Slingshot Archives - Metro Grade Goods

Posted on December 2, 2016 by Metro Grade Goods — 4 Comments

Metro Made | The Steamplinker Slingshot

It’s been quite some time since I’ve written about another build, frankly, it is tough to live up to last slingshot (The Cafe Racer). In this Metro Made, I dive into a deep custom for my last build of 2016. I’ve been collecting materials for this build for quite some time, from all over the planet. Mainly, brass sheet and brass hardware and brass coated components. When the last component arrived, it was time to start building.

To start, this slingshot is dedicated to OTT shooting, with flats and tubes. To achieve this, the design of the Oren’s tips (which this design was based on) had to be altered. Probably the most unique and often debated feature of Simpleshot’s Ocularis ^® plug system is the rounded tips. While it offers an incredible versatility and ease of banding for various styles of band orientation, my preference for the Ocularis ^® is usually always OTT. Since this build is going to be my 2016 opus and this frame being exclusively mine, I decided to refine the tip into something I would enjoy shooting over, and over and over again.

This illustration you can see the variations I went through to arrive at the final shape. The final tip shape is slightly convex with flat sides and a dip in the middle for the single tube to seat into. The bottom left is what I went with, but without the indentations (a meek attempt at adding wrap and tuck style grooves). The body and handle style remained unchanged, a shape I was very familiar and comfortable with.

Here’s a sample of what I had to work with for details. Some very small 12mm brass cogs, gears and otherwise Steampunk-like accoutrements.

After programing the initial profile, the concept was to use the profile as a template to successively cut and trim each layer of brass, g10, brass, g10 etc etc. This worked out with a few hiccups, but for a complex build like this it can be expected.

The profile also was host to gears, layered at different depths to really mesh into the body. The outmost gears had a 5mm hole which I used to integrate the brass Philps screws.

Rough cutting the rest of the materials. At the core is a 3mm thick brass sheet, flanking that is a .03″ black g10, then a .5mm brass sheet, then purple .03″ G10 and finally an outside scale of .125″ black G10. Did I confuse you with the Imperial/Metric measurements? Try working with them…the reason is that they are sourced from all over the world, so the Metric 3mm and .5mm brass was sourced overseas, while the G10 was source from two different North American suppliers. Regardless of system, the final thickness is just a hair over the ideal thickness for the Ocularis ^®plugs. I wanted to create a piece that had colour in it but in a subdued colour palette suitable for the steampunk theme. While purple on its own is quite flashy; however used as an accent colour to black and brass/gold tones, it gives an air of royalty and class.

Each layer was attached with glue and then trimmed closer to the final shape. Then the brass core and before the last layer was applied, brass M3 inserts were set into the body to so that the screws could be put in place when it was time for final assembly. Unlike most of my excited builds, I took my time with this, letting it sit overnight before trimming the excess material. The Cu-Ren sits next to the Steamplinker as a jumping off point.

The unfinished main body travelled around with me while I did some admin work and shipped out some orders. The more I looked at it, the more things I resolved in my head on how to finish it. Next to it is the Kylo-Ren, yet another Oren variant.

After sitting on the frame for a day (which was mostly to build up the courage) it was time to tackle the brass core with a flush trim bit via the router. My router jig to hold slingshots was crucial for this step as I wanted nothing to do with holding work with my hands near this potentially dangerous step. Luckily with some tweaking of the router bit and feed speed (and some light lubricant on the brass), the majority of the brass and other stacked layers were trimmed away revealing the very attractive core.

The heat of the machining separated some of the layers, no matter, a quick flood with some viscous CA glue and some pressure cured that problem. This also gave a quick preview of what the final core would look like.

With so many layers combining to make the main body, I had planned on peening over some brass rod at the tips, which is what I did. This locked the layers down for good. The added thickness of the OTT tips allowed for two pins per tip.

This next step I couldn’t document very well since it required a lot of hands on manipulation, but the front scale was cut from .185 G10 with the same .03″ purple G10 liner. On this surface a pocket for the maker’s mark was machined and two channels for inlays to be put in. Strips of brass, black and purple G10 were set into place and then sanded flush with the surface to create a faux separation between the handle and the tip area. The channels aren’t straight, they have a slight curve to them, a feature impossible to do by hand but only with the aid of CNC. A quick router trip with .125 bit cleaned up the side and the surface roughed to 100 grit in prep for more shaping and the fine hand work. Having made this shape dozens of times, the compound curves of the shooter side scale is complex but familiar.

Now to flip it over and pay attention to the target side, this is where it got a little crazy. I had to estimate where the lanyard hole would eventually be and select the correct materials to suit the theme. Not only did the materials need to match, but I also like designing these types of features to wear nicely when the slingshot is put on a table or surface or replaced many times into a holster/bag.

So, first was a layer of .5mm brass, then a nice selection of brown ebony (with the grain oriented vertically). Once that cured, the end was ground off with some aggressive 80 grit belt sanding. On that off-axis surface, more brass, purple heart and finally a chunk of canvas micarta. I felt the brown ebony was precious enough to stay within the theme, the purple heart being a natural version of purple tones and the canvas being a little bit of a ‘rougher’ visual texture, it would combine into an interesting composition with the delineated, intersection of brass lines. This is something I’ve been experimenting with for a little while and this was a perfect opportunity to apply it.

Rough trimming the excess material away. The ebony is HARD stuff! The ebony section is pinned in place with a brass rod. The offset purpleheart/micarta is held in place with a .25″ brass tube (itself offset to the rotation so it won’t be going anywhere)

Again, one of those times when taking process photos would have ruined the flow of creation, but fast-forward to the part where the pinky swell is rough shaped, then tweaked with file work and sanded to 400 grit. Ebony being so hard and oily, it took to wetsanding very well.

Some of my favourite parts about this design is how the pinky swell melds into the middle finger indentation near the center of the handle. This makes for a seamless shape, but the material makes is even more interesting.

Fast-foward view on the front scale. The process is very much the same, rough shape after drawing on the lines and then lots of file work, abrasive papers and some cloth backed 400 grit. The design of the front scale has been refined over the various iterations of the Oren, but essentially it’s a removal of all the material that would hit a hot spot in the palm. By placing the liner under the thinner scale material, a nice contour of colour is revealed when filing it back.

Test fitting the gears before the final sanding and polish.

I had tried using the MicroMesh polishing system before on a few other G10 frames and the results were amazing, so there was no reason to skimp on the finish for this. After going through the grits (1500 to 12,000), the surface of the g10 and wood would be as smooth as it would ever get without polishing. The trick to G10, I found, was to leave it unpolished and use some mineral oil to return the jet back colour to the surface since sanding clouds the finish. I may still buff this to a high high shine but the high gloss pinky swell, the matte finish of the g10 and the gleam of the shiny brass makes for a combination of textures that I highly enjoy.

I am still waiting for ONE more hardware piece to come in, which put this deep custom slingshot into the next level. Some 10mm ear tunnel gauges. While I sourced 7/16″ G2000 brass balls for the Ocularis plugs, the gear laden era plugs will give the shooter side some interest beyond the maker’s mark.

Despite the ‘proper’ hardware missing, I couldn’t help but take some archival photos of the finished slingshot.

If you’ve made it to here, it means you are truly dedicated to slingshots! Thank you for reading!

• Stay True •

-Metro/Eric

Posted on March 2, 2016March 8, 2016 by Metro Grade Goods — 1 Comment

Metro Made | The Spanish Cafe Racer Slingshot

The best thing about slingshots is that it is like a very large pie, each slice a different flavour. One particular slingshot flavour is the legendary Spanish target style shooter. The Spanish Target Style has more in common with Olympic style free pistol and recurve bow target shooting than slingshots. With ergonomically shaped handles, adjustable band position and sights, the Spanish Target Style slingshot is a very tailored fit to the shooter.

It has been a very long time since I’ve posted a build log, just too many projects and too many details to write about. This late but better than never, post is one I am very proud of. Here’s the story of how the Spanish Cafe Racer was created.

Cafe Racer, after the classic naked sport bikes that favour speed over comfort for short races between watering holes.

The idea came to me after I had finished another Spanish style slingshot, named the Jawa. It differs from other Spanish style slings because it has a moveable sight and fixed band positions. Typically, the bands are moved to match up with a fixed sight. The grip is a hybrid pinch/pistol grip which is based off a semi semicircular hand web shaped and a long pistol style handle.

I had received a connector rod and piston combination (from a Triumph TT 600 for you motorheads) I was more excited about the piston than the con-rod (which can be converted into slingshot as well). The circumference and and over all shape was going to be perfect for the project I had in mind. Here’s a photo of the final product so you have an idea of where we are going.

Here’s a shot of what kind of raw material I was working with: a solid cast aluminum piston head. The recesses for the con-rod movement were a great jumping off point on the design of the handle.

After some very careful planning and digital alteration of the piston head (lopping off a section of the front of it). This is what I came up with for the front fork plate, handle and base plate. The fork plate design is a meld of aesthetic and functional choices; the fork tips, the index finger hole, attachment holes and maker’s mark position ALL in one part. The handle is a 3 part sandwich where the middle section is sunk into the base of the piston and held in with the con-rod pin.

A quick and dirty digital mock up of the fork plate. It is out of scale, but the general idea was there. After 2 days of planning, I was ready to go into the shop and start crafting this speed machine.

–Shop Time–

First step was to mill off some of the piston head to reveal a face to attach the fork plate to.

Then it was time to cut the for plate, something very satisfying seeing a part you’ve poured hours into designing come out exactly how you imagined it. 3mm carbon fiber was the material of choice for its high strength properties.

The first unholy matrimony of the fork plate and the piston. At this point…I was getting really anxious to surge ahead.

Front view

The plate is attached via two M4 inserts pressed into the newly milled face, you can see them peeking when looking under the piston (the brass bits).

The handle blocked into place waiting to be shaped.

I had thought I had chosen some mahogany, but mistakingly selected some teak. No matter, teak was a better choice in the end. Funny thing happened when I laminated the three parts together, using only a thin CA glue as the bonding agent, the CA glue fizzed, hissed and froze nearly instantly when the two parts where pressed together. Never seen that happen before.

After some quick shaping, removing only what was needed to make it work, the handle was done. Soaked in linseed oil for 10-15 mins and buffed with some paste wax.

A 3/4 view of the handle installed.

The right side view shows that the the handle profile wasn’t altered since no fingers or palm would be touching it. However you will notice that the middle finger curve is subtly in place as is a little notch for the ring finger. These two little recesses were crucial for the proper and repeated hand placement when gripping this frame.

The rear view shows that the left portion of the handle was removed so that the meat of the palm has a place to sit and support. The peg on the right is a place holder for a bar that will span the entire width of the slingshot, serving as a finger and thumb shelves.

You’ll also see a the base plate was cut from some loose fiber filled carbon fiber place. The plate sandwiches the fist and handle, so the more I squeeze with my ring and pinky fingers, the more the frame snugs up into my palm.

This pic shows the M4 inserts for the fork plate attachment and the two M3 inserts on the top that will become the alignment pins to ensure the frame is square to the target.

The machining process left the edges sharp and there were some stubborn carbon deposits on the top of the piston head so into the tumbler it went for an overnight toss up with steel pin media.

While that was working itself into a frenzy, a quick sight pin was made from 1mm carbon fiber board. This will attach via the same screw as the fork plate attachment.

The edges of the piston head where the gaskets used to be were too sharp so some thin leather with some contrasting stitching was applied. This covered up the sharp areas but also gave it a nice upholstered look.

The last thing to add was a 2.5mm hex tool (made from a 1/4-20 thumb screw and a saw off section of Allen key). Some details were hand filed into the head so make it look like a gas cap.

First 10 shots on a 2.4″ target, 3 landed in the circles and 1 bulls eye.

A final spit polish: some orange M4 washers, a threaded rod with carbon fiber sleeves and .75″ aluminum balls completed the Spanish Cafe Racer. Enjoy the slide show!

See you all very soon at the first Annual South East Slingshot Tournament, March 11-12!

If the pictures weren’t enough, here’s a video of the road/range/shooting case I made for it!

Posted on October 5, 2015October 5, 2015 by Metro Grade Goods — 6 Comments

Enzo Carbon Fiber Hydra Slingshot

I’ve had this carbon fiber board in my shop for half a year, waiting to be made into something awesome, my recent CNC adventures (see my LunchBox CNC instructable) have allowed me to actually USE this material and take advantage of the awesomeness that is CF.

The CF board I have has one shiny side and one rough side, this is likely why I was able to buy it so inexpensively. To achieve the correct thickness to start with, two sections of this board were glued together to make one solid sheet of material. I rough cut the 4″ wide board with hack saw, you always want to use a saw with lots of teeth so not to tear out the fibers.

Using 5 min 2-part epoxy and a similarly sized sheet of vulcanized fiberboard (plastic cardboard spacer material), the two halves of the sheet were bonded and clamped to cure for 24 hours.

When using epoxy, it is important to properly mix the two parts for a good amount of time. 5 mins epoxy is a WORKING time, not setting up time, so take an extra 30-45 seconds to really whip it up. Normally, you would key the mating surfaces so that there would be a lot of texture for the epoxy to grab on to, in this case, since the CF was already textured and rough, that part was already done.

It also critical not to put too much pressure on your parts, you want good coverage and bonding of the epoxy, but you don’t want to squeeze it all out with too much pressure from clamps. I use a number of pony spring clamps of various strengths, light duty ones to light clamp on the sandwich so not to have the two parts skate around. Then slowly add more medium duty spring clamps until the pressure is evenly distributed.

This is where I may lose some of you…but stay with me..it’ll be worth it.

This slingshot design, which I call the Hydra (see more Hydras here) is one my favourites. I basically designed it to be done with metal or a composite like CF or G10. The skinny arms just can’t be made from wood. I altered the design a bit to accept a special attachment method for leather band tabs.

Leather band tabs are just another way to attach rubber to a slingshot frame. A piece of leather is either lashed, glued, clamped otherwise attached to the slingshot tip and then the rubber is tied on to that, it’s a very common attachment method and favoured by the Spanish target style of slingshot.

My method of attaching tabs to a frame is called the ‘Tapped Tab’, because the frame’s tip is tapped with a 1/4-20 thread and the tab is attached via a bolt. The tab is also threaded through a horizontal slot to equalize the pressure on the fork tips. This type of attachment requires the materials of the slingshot to be very strong and stable, typically aluminum or a composite.

To design the slingshot, I used Adobe Illustrator to create the 2D pattern and accurately size the holes. From there, the pattern is saved out to an SVG (scaleable vector graphic) and opened up in to MakerCAM (a free CAM software to generate G-code). MakerCAM will allow me to program the feed rates and types of cuts I want (pockets, drilling, profile cuts etc).

I believe I ended up with these settings:

15 Inches per Min Feed

5 Inches per Min Plunge

.05 Depth of Cut

It was slow, but it was very accurate.

I used my LunchBox CNC to cut it out.

Instead of tapping the CF directly, I opted for a press fit threaded insert. I also made holes to accept a M3 threaded insert for attaching the handle scales to.

Then it was time to press ‘start’ on the CNC machine.

The bit used was an 1/8″, single flute, downcut carbide end mill. This gave the biggest chips and the downcut left the surface very clean.

I chased the bit with the shop vac hose to eliminate any carbon dust and debris that may fly away during the milling process. With the bit spinning at 10,000 RPM but taking very light .05″ cuts, the job took 23 mins. The result was a very clean and accurate representation of the 2D CAD model.

The final thickness of the CF slab was .47″ and the 1/4-20 threaded inserts are .5 so I had to shave off .03″ on with my lathe to get them to seat flush with the surfaces.

When installing these inserts, it’s easiest to thread a bolt into them and then press them into place. I added a bit of CA glue when it was 2/3 in to really set them into the hole.

The M3 inserts (can be found on eBay for a few dollars for 100’s) are 10mm long and were just pressed into place. M3 screws are very common as well as most electronics are assembled with that size screw.

The Hydra is what is know as “pinch grip side shooter”, the deep round sections near the middle are pinched between the pointer finger and the thumb and the frame is held sideways (forks parallel to the ground). The slingshot is already looking pretty cool, but it’s a pain to hold. To make it a more comfortable shape, the edges need to be rounded and some more beef needs to be added to the handle area.

I didn’t take any pics of the CNC cut of the handle scales, but the process is essentially the same. The material is 3/16″ thick haircell texture ABS sheet. My previous incarnations of this design had 1/4″ thick scales, but for this special one off Hydra, I wanted the scales to blend into the frame.

My though process about using the 3/16″ thick ABS was if I used a 1/4″ round over bit, the entire edge and a tiny bit of the CF frame would be rounded over, resulting in seamless transition between scale and frame. It worked out very well.

After shaping both the scales and labeling them to their mated side, I focused my attention to the frame. I switched to a 3/16″ round over bit and sped up the router speed. I took careful note of how far to plunge when machining the ‘arm pit’ areas so that the transition between the raised scale and the flat frame would be even and smooth. The same amount of attention was paid when I was machining the inner fork area.

CF is nasty stuff, if you sand it, it turns everything black and the dust is awful. To avoid this, you can wet sand. It takes a bit longer but the result can be washed away and the CF dust is virtually eliminated.

The CNC machine and the router left the surface pretty smooth, but really give it a nice finish, sanding it required. I wet sanded with 150, 320 and 800 grit papers. This evened out the surface and preps it for final polishing.

The scales will be attached with some counter sink 6mm long M3 black oxide screws.

We are almost there.

The ‘end grain’ of the CF is now exposed and to make it a bit more stable, I sealed the edge with some cheap, super thin CA glue. This is a pen maker’s trick. Be in a well ventilated area wear nitrile gloves. You just need to put a tiny drop of glue on the edge of the slingshot and rub it with a single finger till it dries. This should only be seconds.

Repeat the process until all of the edges are coated with a thin layer of super glue, BUT if you are using ABS, be careful not to use it on the ABS surface as CA glue reacts to it and will ruin any smooth surface.

Now it’s time to really make it shine. I use one of my favourite tools, which isn’t even a proper tool at all, a nail buffer. With 1000 grit on one side and 4000 on the other, the foam backed buffing stick is the perfect low tech polishing tool. Slowly but surely buff the whole surface with the 1000 grit side and then follow up with the 4000 grit.

Once you’ve achieved the level of shine you like, take an alcohol swab and wipe off the slingshot. This will remove any transfer of materials and clean up any residues. DO NOT USE ACETONE, acetone will react ABS and just melt it.

I also shined up the brass screws I am going to use to attach the tabs, the same buffing stick was used

I don’t know about you, but I photograph my work as soon as I am done with it. This way, it’s in the best possible condition it can be in. This project was so much fun and it really tested my materials knowledge, having never worked with CF before, I relied on my previous knowledge of composites and plastics to inform my machining strategies.

I am quite pleased with the result and the heirloom quality combined with the high tech material and methods make for a great end result.

Thanks for hanging out and I hope you get something out of this.

-Eric/Metro

Posted on May 27, 2015 by Metro Grade Goods — 1 Comment

Metro Made | The Molly Pick-Nick Slingshot

A few weeks ago, I was fortunate to come across some new materials gifted to me by a fellow slingshot crafter, something called GPO3. GPO3 is a loose fill fibreglass composite, commonly used to insulate electrical installations. Like all things that are flat and tough, most times knife makers will use it to graft onto their handles. GPO3 has a nice consistent red colour throughout with some subtle, long fibrous texture.

When I got my hands on it, I didn’t know what to do with it, use it as a core, use it as a scale material. I had a few thicknesses, 1/4″, 1/8″ and a 1/16″ stock. I finally go to making something, using the 1/4″ as a core, call it an experiment. GPO3 is strong enough to be a stand along slingshot as the long fibres combine for a very tough composite with very little flex.

What came out of the experiment was this:

Resemble anything? Did you think…hot dog? I did. So that was aptly named the Hot Dogger. Here’s a quick video of me shooting it.

I enjoyed the feeling and look of the GPO3 so I went for something a little more ambitious, something kind of colourful and not everyone’s taste but I felt I needed to make something for once and not have to post rationalize features or design choices. This would be a through and through concept to completion build.

The inspiration, this picnic pin-up painting by Harry Ekman.

So let’s start with the core of it. Recently, I have heavily favoured the OTT Tapped Tab Tyton slingshot. I can shoot it sideways and upright and have great success for both, each have their advantages and disadvantages. So to make this build extra special, I decided to stick to something I knew.

I am going to skip the part about laminating, if this is your first time reading, you should check out this post to get up to speed: The Spanish Knight. The 1/4″ aluminum core was laminated with some specifically chosen coloured liners followed by an outer layer of 1/8″ GPO3. The colours chosen by the most common, and my most favourite hot dog condiments: yellow for mustard, red for ketchup, green for relish and white for sauerkraut. The laminatatins are all held in place 4 solid aluminum pins. Here you can see the partially finished core with pins glued in. Pretty standard stuff when gluing differential materials together.

Leaving to set up over night and coming back to it in the morning, the pins were ground flush and then the edges of the entire slingshot where passed over a 1/8″ round over bit on the router.

Now..the fun part. Instead of just using regular maple, I went with a nice selection of quilted curly maple.
Using small strips of spacer material, I built up a candy stripe pattern found on old school drinking straws and then selected a small bit of zircote to reference my favourite picnic beverage, cola.

Here is the slab, overflowth with epoxy resin to fill in any gaps.

The back side scale was done in much the same way but I went back to the pin-up image to pull some colour choices. Some yellow heart from her dress, the white and blue from the picnic blanket. At this point, I’ve decided her name is Molly, so shall the slingshot’s name be.

Letting the epoxy slabs cure over night once again, and in the morning sand the surface flush to reveal the contrasting, almost graphic novel style material slab.

Once the shape of the scale was traced out on one of the slabs, I taped them together to work on them simultaneously. This also made pulling them across the router bit a lot easier. These were sanded to 600 grit and it was beginning to look like I was going to pull it off.

Laying the scale on top of the core, it was all coming together.

…and a quick mock up to see how it would look. The hot dog is strong with this one.

I had previously posted about a new tool I got in the shop, a mini laser engraver. To add more detail, I etched an ant on one scale and a scaled down (6mm) Metro Grade skull on the other.

In the above picture, I already had attached the scales onto the frame. Seeing how these were decorative and weren’t structural, I felt there was no need to pin them into place. CA glue (super glue) bites onto GPO3 very hard and is a fairly secure bond.

Once everything has set up and permanent, it was finishing time. The GPO3 really needs no finishing, but the surface is dry, dull in colour and often will shed tiny fibreglass shards that will itch for days, so something to tame the mane would be helpful. On the Hot Dogger, I used just paste wax to finish the GPO3 and it worked very well, so I knew that waxes would help. The wood needed an oil and wax finish so my best choice was to use my trusty linseed/beeswax combination finish, literally named Tried and True (available at Lee Valley).

I slathered it on liberally and let is set up for about an hour before touching it, then I hit it with some heat from a hair drier to open up the fibres of the wood to let the finish penetrate and liquify the wax too. The colours really pop when the finish gets applied.

While I waited for the finish to set up, I made up a set of BB bands and selected some hardware to attach them on to it. These particular brass thumb screws are $4 each, but are well worth it.

Rubbing down the wax for a final time with clean cloth, it was time to take Molly out for a nice sit in the grass.

I hope you enjoy this build, I know I did. It’s not for everyone, but then again, I usually build what I like to see and hope others enjoy it too.

If you are headed to the 2015 East Coast Slingshot Tournament, you will be able to see this and many more of my personal custom slingshots in the flesh. I will also be hosting the Craftsman Roundtable discussion with master builder Nathan Masters of Flippinout Slingshots and SimpleShot.

-Eric

Posted on May 17, 2015May 18, 2015 by Metro Grade Goods — 3 Comments

Metro Made | The Wormhole Attachment (Lumbri Tyton Slingshot)

I recently bought a new Chinese cast aluminum slingshot called the Tiger Scorpion, while the attachment system wasn’t new (I have a few frames with the same style tip), the shape was kind of neat.

So I banded it up with some bb tubes and played around with shooting it..it was neat! I had set it up with a single tube with a ball in the tube end, then after one particular shot, the single tube slipped into the big hole as well as the small hole….bling..lightbulb. I quickly undid the bands and ‘wormed’ it through both the big and small holes, terminating at the small hole. Kind of like the Wave attachment.

Boom, instant OTT single tube attachment…this got me thinking..the Tiger Scorpion, while cool, wasn’t 100% what I liked. What I do like is my Tyton. I have practically packed up everything to send to Peppermack of Cracked Pepper Cataplts, so when the urge and inspiration hit…I was nearly devastated, BUT I have never been so happy to have found two extra cores in my shop.

I took my digital file of the plain tipped Tyton frames I got cut for modding and discovered that there would be room for a big and small hole set up like the Tiger Scorpion, but what I wanted to do was make the smaller hole, even smaller than it was on the T/S so it would be more of a friction fit with no ball in tube needed. Thus the Wormhole attachment was born, and the namesake for this slingshot, the lumbricus terrestris: an earthworm.

I started by gluing up two plain tipped Tyton frames with a blue spacer in the middle. I pinned the top two pin holes with aluminum and peened them into place before flush sanding the face.

I layed out the new hole patterns, a big 5/16 and a smaller 3/32, with connecting channels to the outside of the fork tips. This would allow for single tubes or looped tubes if I fancied it. From there, I shaped the tips till they were rounded and a divot was filed into the top of the tips to center the bands. I also shaped the finger and thumb grooves like my other Tyton mods.

You can see here how the Worm attachment works. Since the band makes a 180 degree turn before rolling over the tips, there is no way the band will slip out.

From there it was time to dress the Lumbri up! I shaped a small bit of ‘patriot’ pattern Kirinite. It was just wide enough to get to the base of the handle. After profiling it, I resawed it into to identical halves and flushed the faces. From there shaped and finsihed the front edge of the scale that touches the surface of the slingshot, like building a knife since you can’t access that area with out really damaging the surface of the slingshot.

After fitting a 1/4 brass tube a 1/8 pin, I decided to try something I’ve seen 1000’s of times on custom knives, the very popular Anso texture pattern, an intersecting series of scalloped grooves. After plunging in for my first couple of grooves, I could already tell this was going to look sweeeeeet.

The Anso pattern is named after Jens Anso, an fellow industrial designer, custom knife and gear maker. Jens first did the pattern and has since been used on many custom knives and equipment. Here he is adding this trademark texture:

Rough cut and shaped scales.

The rest are final pics, I didn’t want to ruin my work flow as the dust from the Kirinte is heavy and gets EVERYWHERE. In the end, I buffed the scales and matt finished the aluminum. I also added a Paduak makers mark and coated it in superglue to seal it up.

Thanks for stopping! See you at ECST 2015!

-Metro

Posted on April 21, 2015April 22, 2015 by Metro Grade Goods — Leave a comment

Metro Made | Cutting Band Grooves in Slingshot Forks

This is a short tutorial and some would consider it a minor detail, but as they say, the devil is in those said details. In this Metro Made, I show you how to I cut band grooves in slingshot tips.

Band grooves are important as they aid in the attachment of bands when using the wrap and tuck method. The grooves also improve safety as they seat the band tying rubber and prevent it from slipping off the tips of the forks. Having evenly space and equally spaced band grooves improves the accuracy of the slingshot as the bands would be tied equally on the slingshot’s fork tips.

How far from the fork tips edge is completely up to you but I generally go with a minimum of 1/4″ish from the edge of the band groove to the tip. It really depends on what kind of bands you shoot, how much band attachment rubber you tend to use…but here’s what I like. I enjoy using single cuts of the thinner Therbands, blue & black, for a lighter draw and faster retraction, as such I don’t need much of a band groove, but I still need one there.

I begin by marking where my band groove’s center will be. To mark them evenly on all the sides of the fork tips with the same distance from the tips, I use my trusty drop compasses.

Here, I’ve used my blue lead to mark. Why blue? It’s the first drop compass I picked up.

I use a very fine tooth razor saw and cut down the line. With the a lot of teeth per inch, the razor saw won’t cut much but the surface of the metal or wood, but the point isn’t to cut the through the tip, just to make the blue line indelible.

The blue line is no more, but replaced with a shallow, straight cut.

I then pick up a triangle file and seat one of the tips and pull 4-5 stokes to deepen the line into a shallow groove. You want to open up the material so that a round file will have a place to sit in and not skip around. I typically use a 1/8″ diameter round file but if you want a bigger one like a 3/16 or 1/4 groove, you may want to go a bit deeper with the triangle file to ensure the larger round is placed accurately.

Remember, slow is smooth, smooth is fast. You can check your work after each stroke or two, if you mess up, you can correct it.

Now for the real magic.

Use the round file to open up the channel to a round groove. I usually don’t go past 1/2 the depth of the file, approx 2/5 of the way. Again, slow is smooth, smooth is fast. Check your work as you go, if it’s deviated left or right, you can correct it.

After about 10-12 strokes with the file. If there is any material blowing out the back side, you can run the file in the opposite direction to clean it up.

Now do this 3 more times and your band grooves are good to go!

You could also do this to the front and back of the frames, but I usually don’t.

A better look at the whole package.

In case you were wondering, the frame is a new aluminum core we have yet to release, based on our Tyton design.

With some Theraband Black tied to it, a 15mm-10mm tapered cut at 7.5″ active length, my formula for deadly fast bb bands.

So that’s it.

A quick demo of how to cut accurate band grooves on pretty much any board cut style slingshot.

Thanks for reading!

-Eric

Posted on April 4, 2015March 30, 2015 by Metro Grade Goods — 1 Comment

Metro Made | The Italian Job Slingshot

Since I started making slingshots, there have been a lot that have gone out the door. More and more I have less and less time to appreciate them before they do leave my shop. It was time to build one for me and me alone, one for the ages, one for me to take to tournaments and show off my skills as craftsman. I call this build…the Italian Job.

This all started when I came across a unique material, a vintage, hand cast acetate tortoise shell made by the famous Italian house, Mazzucchelli. This amazing fluid, subtly textured, semi transparent material is common used for eyewear but I managed to acquire a few sheets at 8mm thick. This was the anchor to my flagship slingshot.

I used one of my most comfortable frames, a modified Mule (designed by Mark Toddy) I like to call the Three-Trick-Pony. The tips are able to use three types of bands, hence its three trick monicker. The 1/4″ thick aluminum frame was scuffed and then tortoise shell was laminated onto it. I then mixed up some more epoxy and incorporated some espresso beans which filled the hollow voids in the aluminum core. This was the 2nd nod to the Italian theme.

Once the epoxy had cured, a quick sanding on the belt sander made the cast beans flush with the surface of the frame.

After trimming and sanding the tortoise shell flush with the frame’s perimeter, I chose to use another very unique material: C-Tek. This white C-Tek was chosen as I felt it mimicked the hexagonal ties found in many Italian cafes. It was at this time, the pin holes where filled with brass tubing.

Separating the C-tek is a red vulcanized fiber spacer, this will play into the theme as you will see later.

The pattern of the tortoise shell beginning to show up.

The espresso beans are barely visible, but after some buffing, they will be easily seen.

A close up of the C-Tek. The opaque white with aluminum honeycomb really does come out looking very nice.

For a better ergonomic grip, a pinky stop made of highly figured olive wood separated by another fibreboard space, but in emerald green. Completing the Italian national colours, the green spacer helped interface the natural wood material and the synthetic C-tek.

I didn’t take too many process pics of the shaping of the tortoise shell, but I used my favourite shaping tools, an Iwaski file followed by an ultra fine 1/2 round file then various grits of sand paper till I hit 1000. I then use a hard buffing wheel with some green compound and buffed it to a dull shine.

In certain lights, the cast beans are much more visable. You can also see how I used some tin foil to back the casting to prevent the red from showing up.

Then it was time to shape the C-Tek. The soft resin behaves poorly to power tools since it heats up very quickly so again, it was time to use the Iwasaki carving files and various grits of sand paper. I could only do so much shaping as the epoxy for the pinky stop was still curing.

Before rough shaping of the pinky stop, the corners and bulk of the olive wood was bandsawed off.

The olive wood sands very nicely as it is very oily and dense, so the belt sander was a good way to do a very rough shaping into a tear drop shape.

There is no really fast was of doing a palm/pinky swell. Manual tools again come to aid, as the roundness of the pinky swell took shape, the swirly grain also revealed itself.

After some high gri sanding, and then some light buffing, this slingshot is complete.

Sexy archive photos, note the Metro Grade skull etched into the pinky swell

Thanks for reading yet another slingshot build.

-Eric

Posted on March 29, 2015March 20, 2015 by Metro Grade Goods — 3 Comments

Metro Made | Bloodlines Slingshots – Meeting Prince Charles

May 21, 2014. The Prince of Whales visits the shop, I am tasked to present him with a unique gift made in the shop. I am proud to say, I have 2 Metro Grade slingshots in the Royal gift collection.

I call these two slingshots, the Bloodlines, as you see, one is for Prince Charles himself and one for his brand new grandson, George. These had to be unique, classic and well crafted, so I didn’t fool around with an unfamiliar shape, I went with my classic Capuchin side shooter.

My goal for the pattern design is to meld a little bit of Brit with a little bit of Canuck. Using the Union Jack as inspiration, maple, paduak and walnut is utilized to make a slightly modified version of it. Here you can see the laser cut maple as the skinny lines of the Union Jack are formed.

As the each piece of paduak is set in place, the ‘Jack comes to life.

As I said, a little bit of Brit and a little but of Canuck. After dry fitting and making sure all the parts fit, it was time for glue up.

Once the glue was set up, the surface was face sanded to reveal the gestalt pattern of the Union Jack being anchored by a purple heart Canadian Leaf. The paste at the bottom is a bit of ghetto wood filler for some gaps left in the lay up.

On one slingshot, I decided to document the date, the event and the location. Also the Assentworks logo is etched into the handle. On the 2nd slingshot, some Metro Grade branding as well as “George”, for obvious reasons. Another purplehear maple leaf would later fill George’s slingshot’s handle.

Some quick router work on the edges and some final sanding before a couple of coats of sealer.

Here are the archive photos:

..and thanks to Tracey Goncalves for the images of the actual hand off. My exchange was quite short, a mere minute. His majesty was ill, runny nose to be exact so his voice was very quiet. He asked, “are these catapults?” to which I answered “yes, one for you and one for your grandson, George”. He explained how he used to play with one as a child, good to know.

It was an honour to meet him.

It’s funny to review those photos and look at my face….I can’t make a single serious face even when meeting royalty.

Thanks for reading!

-Eric

Posted on March 16, 2015 by Metro Grade Goods — Leave a comment

Metro Made | The Taser PFS

This project, titled the Taser PFS, couples a number of things that I love: machining metal on a lathe, working with stabilized wood and using leather tabs for attaching rubber to a sling.

This all started when I was poking around YouTube trying see what other country’s slingshot tournaments looked like. I came across this Eurocup coverage:

Later in the video, an interesting designed slingshot came up. It looked like a wood handle with two brass posts where a bridge attached hosting a center located sight pin. The posts and the bridge compressed two short leather tabs that attached to the rubber tubing. Needless to say, in the short few seconds that I saw it, I was intrigued.

So I set out to make something unique…not exactly like the one in the video but something I could pocket, enjoy with a variety of shooting styles and best of all, something I could challenge myself with. Over the course of my time as a designer, I’ve amassed quite the collection of materials and I am not proud to say that my stock area is more like a hoarder’s dream, and a organizer’s nightmare. For this ‘Taser” I wanted something narrow, but sturdy. A thick slab of red dyed, stabilized sycamore wood that was booked matched to be a knife handle scale was suitable for this project.

The sycamore scale slab was about 1.5″ wide, .5 thick and 5″ long. I didn’t need 5″, more like 3.5″. First thing first was to machine the sycamore and since it was stabilized with resin, this was pretty easy since it worked more like plastic than wood. BUT before machining the wood, I needed to make the posts.

I wanted taller posts than the one in the video since my plan was to attach these onto the wood from underneath and have the leather tab bolts, independent to the post. These ended up being about 1.25″ long with a 1/4-20 thread on the top tip and 10-24 threads on the handle attachment side. I also knurled the top of the tips so there would be a little bit of grip, it also added a bit of a cool look to the final product

Once I had the posts all sussed out, it was time to machine the sycamore. This was pretty easy, as previously mentioned, the stabilized sycamore’s resin content really smoothed out the cutting. The handle was made into a paint brush shape and in the shoulders two holes to attach the posts were made. The holes where counter sunk on the underside to recess the 10-24 screw heads.

After the initial fitting, the edges of the skinny handle were rounded into a generous radius. This provided comfort and a cool reveal of the sycamore’s neat grain structure.

After rounding, there was an element missing from the handle’s base so I added a 1/2″ aluminum tube to serve as a lanyard hole should I choose to add one. This again brought another element of machine aesthetic to an already machined product.

At this point the Taser was done, serviceable as a target destroying tool. The last thing to add was the sight bridge, like the one in the video. It’s an added feature that if it didn’t serve the slingshot well, it could be removed. To achieve this bridge, I turned to another machine; the laser cutter. I chose to cut 1/8″ ABS, since ABS is more shock and impact resistant to other plastics that can be laser cut. Acrylic would shatter and polycarbonate cannot be laser cut. ABS’s soft structure gives when struck, which is good since I needed to tap a small 6/32 bolt into the top.

This pan head bolt’s groove was slotted with a file to accept a 1/32″ acrylic rod which, when hit with sunlight, will glow red. This served as a compound bow style sight pin. This worked very well in both concept and action, however, my preference in the end was to leave the sight bridge off.

Here’s a pic of how the sight pin looks like with some light shining on it. The coolest thing about attaching tabs under compression like this is you can shoot with the tabs rolled OVER the tips like at true OTT (Over-the-top) configuration when shooting this frame sideways, or you can pull the tabs straight back and have it like an upright PFS (pickle-fork-shooter).

Both are fun to shoot and in the end…isn’t it all about how fun it is?

After etching the Metro Grade skull into the surface of the sycamore, it was time to take some juicy archive photos:

Thanks for reading another Metro Made, I know you have a choice to read other blogs so thanks for stopping by!

Stay tuned for even more slingshot builds and Metro Made posts.

Posted on March 9, 2015March 9, 2015 by Metro Grade Goods — 1 Comment

Metro Made | Tap & Tab Figure 8 Descender Slingshot Build

I am back!

January and February kicked my butt.

After what feels like an eternity, I return to the shop for a short build and an alternative take on the popular climbing figure 8 descender hardware. The last time I tackled one of these, it was more of a TTF, tubes affair. This time around, I do a little bit more machining to achieve an even more refined version of the classic slingshot shape.

Posted on December 23, 2014December 24, 2014 by Metro Grade Goods — 5 Comments

Metro Made | Mini Router Table Box

More times and not, I enjoy roughing out curves, fillets and chamfers by hand. However, there are times when the might of a router with a proper round over bit is the best ‘route’. When I sought out a small trim router to suit my needs, something amazing came into my sights.

Cruising around the internet, I came across the Ryobi One+ battery powered trim router. At 5A, it’s plenty of power for slingshots and other small projects, and the best part is that it interfaced with my already large collection of Ryobi Li-ion batteries. At $50 a piece, they were inexpensive enough to get a few to save on set up time. I had the idea to build some modular boxes, router boxes, router boxes that would sit on a stand with different tools set up so I could hot swap them out when I needed.

I started by using an online resource for designing finger joint boxes, my plan is to make sorta of a square hat box with the router base sitting on the top. I entered the dimensions into the online box maker and out spit a PDF of the box. After taking the file into Adobe Illustrator, I measured the outside dimension and then generated another box, this would become the lid. I digitally chopped off the top of the base box and then lopped off the bottom section of the lid. This left me with a pattern I could start dropping features onto.

The first thing was to figure out the orientation of the tool. The Ryobi trim router doesn’t have a flat base parallel with the surface of the base, this is meant to be a hand held tool, not stationary. The base didn’t matter, it only means that it would be suspended in the box. This did two things, it allowed for height adjustment of the bit (no need for a complicated lift system) and would also allow for the router base to be level with the box surface without bracing. Measuring the base of the router, it was a 9cm square with about a 3/8″ rounded corner, so that’s what got drawn on the top of the lid. Directly under the layer is another layer that would support the head and also index the router so it would always be in the same position. This is a lot of reading without much photographic explanation but it was such a fast process the later images will make sense after reading this.

The second thing was the on/off switch, being a battery powered unit, the front of the tool needed be accessible so that it could be turned off and on while in the sealed box. So locating the switch and making a generous hole in the front panel of the bottom box was done. A rotating switch plate would cover the hole so increase the dust collection effect of the vacuum…..

Which brings us to the third feature, a dust collection port. On the back panel, a 2.25″ hole was located so that a hose could be attached to have a down draft effect. While a SOME chips may make it away from this vacuum, most will be carried away. Two additional layers of material could be glued to the inside to create a .75″ flange so that hose would have something to grab onto.

Ok….so after this was designed in both my head and in 2D, it was time to prototype in MDF. Throwing a sheet of 1/4″ MDF into the laser, one by one the panels were cut out. On top is the router with the big battery.

First cuts of the first panels. You can see the plate on the near the bottom of the sheet, it’s the indexing ring and support.

First dry fit of the parts. The finger joints were actually sized for stock that is .235″ thick and the MDF is .255 so they don’t line up here. Not a big deal since the MDF was just used for sizing and for first fitting.

The router clears the bottom nicely and will allow for about 3/4″ of travel downwards.

After editing the files to change a few details for alignment, it was time to move to some Baltic birch. You can see the indexing plate is now round, I forgot to account for the inside edges of the box. Ideally I this would of been made out of 1/2″ plywood, but the laser has trouble cutting that thick of stock. With a 10″x10″ foot print, the box will be plenty stiff.

Dry fitting the plywood parts. You can see the beginnings of the dust port near the bottom of the box.

I should note that I made two of these boxes, one for each router, and my 2nd one went 4X faster like with any multiple build. The glue joints on the 2nd one are much tighter, I previously hadn’t worked with so many finger joints at once. I also sanded the edges to get rid of the burning PRIOR to gluing on the 2nd one.

This is basically it. The rectangular hole on the front is the switch hole, this got lengthened by hand later to adjust for the bit height. The support/indexing plate was glue in place and further reenforced by 4 countersunk screws.

A shot of how the router looks like suspended by the support/index plate.

A quick zip on my other router table to cut the edges down and it was time to make a second one. Next to the first box (on the left) is the second box. Like I said, it was 4X faster to make the second one.

Once the basic form was made up, it was time to address some performance details. First, the switch hole cover. No Metro Made project is complete without the Metro Grade skull.

This is simply screwed in place (the hole on the skull plate is bigger to allow for rotation).

I knew the routers would likely have a lot of vibration and with such a light weight box, it would be amplified. To combat this, two bricks were put inside the box to weight it down and some rubber feet were installed on the bottom to dampen the vibration. This also makes the whole box very sturdy when in use, less fear of it tipping over with the center of mass, well below the table’s surface.

The best part about these boxes is that they are BOXES! which means they are perfect for storing the adjustment tools. I don’t know about you but I have a small collection of cheap tools, so leaving this small 8mm socket wrench and the bit adjusting wrench ready to be used INSIDE the box is great. Some commonly used bits can also be stored inside the box, I have to make sure they are weighed enough so that they won’t get sucked into the dust collector. This is also a good shot of how the dust port looks like, two additional layers of plywood make up the port.

To lock the lid down, I used two 1/4-20 bolts with a flower knobs on either side that correspond to two slots cut out of the lid.

Here are the slots. On the underside of the lid, on the inner corners, a thin 1mm cork strip was glued in place to increase the contact of the lid and the box. This should dampen the vibration more and also make for a better airtight seal.

The surface of the router plate was TOO slick so some 220 grit sandpaper took off the sheen and added a bit of traction for better control. 4 additional screws were added to the router to really suck down the router base surface to the box lid.

One final shot of the dust port.

The first box will be set up with a 1/4″ round over bit almost exclusively so the 2nd box needed a few more details to make it more versatile. Aside from being a flush trim box, it will also be the box I use to cut band groove slots on the tips of slingshots. I have to buy a 1/8″ and a 3/16″ core box bits, but the idea here is that the swinging arm will pivot on one end to increase or decrease the distance from the bit and act as a fence for the slingshot to ride on. The free swinging end gets clamped down by a quick clamp. When I figure out the idea distances to swing it, I’ll make some indexing pins to easily repeat the cut.

Now to install it in the shop. This whole project was spurred when I found this amazing cabinet at my local Re-Store (Habitat for Humanity) for $15. I think it was used as an mail inbox unit, obviously part of a larger installation due to the unfinished sides, it’s very sturdy. I put some medium duty casters just so I can move it around, but when I am using it, I have it blocked up in the front.

It is the PERFECT thing for organizing my thin woods and smaller blocks of lumber.

The cabinet had a lip on the top side, which I actually think was the bottom, which is nice for the router box to rest up against. I freed up the area in front of the wood storage by moving the small blocks to the new cabinet. There is just enough space to get behind there and get the larger planks of stock. The modular boxes allow me to move the whole unit off the base and then move the other box into its place, no need to spend time changing bits.

I know I’ve gone on and on about the dust port but router make such a mess if you don’t control them.

So to close this Metro Made up, a short video of the first run on the router box. I hadn’t installed it on the base.

To celebrate the finish of these boxes, I made this Blood Orange Tyton with it. The smooth radius courtesy of the 1/4″ round over bit.

Thanks for reading and have a superb holiday season!

Posted on December 19, 2014 by Metro Grade Goods — 2 Comments

Metro Made | Rotating Tip Ergo Slingshot

It was time to try something new, something exciting, something….with moving parts. Slingshots aren’t known for moving parts, but it was time to try it out. Rotating fork tips aren’t something I came up with but I did want to take a stab at it and try to make a deadly accurate BB shooter.

I started by designing a shape that is a smaller frame than usual. A pinch grip style with some beefy fork tips. This would be cut from 3/4″ maple so I knew it wouldn’t be a problem for structural integrity. The plan is to drill a hole straight down into the fork tips, tap it when a thread and screw in some machined sleeves.

After transferring the pattern onto a 3″ wide board of maple, it was cut out and sanded to the profile. A 1/2″ aluminum lanyard hole was epoxied into place.

After shaping the grip area with some generous curves, the handle was shaped with some nice crisp chamfering.

A 1/2″ pocket was drilled into the face with a Fortsner bit and a walnut maker mark button was pressed and glued into place.

Now the tricky part, holding the frame in a drill press vice two 7/32″ holes were drilled into the tips. These holes where then tapped with a 1/4-20 tap. After removing the tap, thin cyanoacrylate glue was dripped onto the threads to strengthen them. After the glue cured, the threads were chased with the tap again and more glue was dripped in.

After the glue was fully cure, the frame was dropped into a bath of boiled linseed oil for a 25 minute soak.

Two coats of light polyurethane sealer was wiped on. This was left to dry for some time.

Now that the frame was done, it was time to make the business end of the slingshot, the rotating tips. The rotating tips’ concept is that the bands would rotate on the axis of the fork tips, eliminating the abrasion it would normally experience when the rubber retracts into the frame.

We start by facing some 5/8″ 6061 aluminum.

The tips are going to be 12mm high with a groove of 4mm to help the bands seat themselves nicely on the center.

The toughest part about making rotating tips of this kind is making two identical ones.

Rechucking the tips after parting them off the stock, it was faced and the a centerdrill was used to help start the hole.

Then a 1/4″ hole was bored straight through the tip.

Using a big single flute counter sink, the tips were chamfered so that the machine screws would nest inside for a cleaner look.

Exhibit A…machine screw seated and clean look achieved.

Rinse and repeat.

Now it was time to screw tips into place, adding a drop of super glue into the threads to make sure the machine screw would not back out again. A thin washer was added to decrease friction and make the action smoother. The screw’s pressure was tuned so that the tips would rotate but not wiggle.

Again to the other side. In case you were wondering, the screws screw into the fork tips about 5/8″.

And we are done! Time tom make up some bands.

A band set with some very small loops made up…

A pair of ring expander pliers help stretch the loop out so they could be fixed over the tip.

And we are done!

I am happy to report that the rotating tips not only look super cool, but they also work REALY well.

Some quick shooting of the Capuchin RT with the same aluminum rotating tips.

Thanks for reading another Metro Made!

Happy Holidays!

-Eric

Posted on September 28, 2014September 28, 2014 by Metro Grade Goods — 4 Comments

Metro Made | Spanish Knight aka Don Quixote

Fall is here, which means less time on the range and more time in the shop. This also means more Metro Made posts! In this instalment, we make a slingshot for Gaspar Arcón, one of Spain’s top slingshot target shooters. Not only is he deadly with 8mm steel balls, he’s also a super nice guy and also friendly on Facebook.

We been chatting back and forth for the last little while and we decided to work on a trade. Gaspar lives in the heart of Spain where Olive trees grow naturally, free for the picking. He often goes out and collects forks from these trees, the wood being a very dense, very figured and shapeable material, perfect for slingshots. A couple of months ago, he sent me a box full of goodies including a huge thick fork for carving and several smaller forks for standalone slings.

Here is the Metro Trade report I did on it:

This Metro Made is my end of the bargain, grab a cup of coffee, this is an exact play by play of the whole process, start to finish.

I started off asking how large Gaspar’s hands were. After knowing how far his grip was, it was time to map out where his fingers would lay and incorporate leather tab band attachments commonly found on Spanish style slingshots. On a previous, top secret project, I developed a slot system for the leather tab that would attach with a screw on to the frame. I used that design on this Spanish Knight.

This DXF file was then sent to the waterjet shop and the frame was cut out of 1/4″ 6061 aluminum, known for it’s good strength to weight ratio but at a relatively inexpensive cost. Once the cores were in the shop, it was time to select the timbers. I wanted this to be a useable slingshot, not too crazy of a jewel that Gaspar wouldn’t be afraid to use it, but something special he would love sharing with his colleagues. I also wanted it to be inherently Canadian. For the business end (the tips) I chose Canadian sugar maple, for a couple of reasons, firstly it’s Canadian, secondly, it laser cuts with very good accuracy.

I also chose a nice red coloured wood, Chakte Kok AKA Redheart. for the handle section of the back side. This wood doesn’t laser cut very well but it’s a section that can be manually cut out. On the front side, I chose a nice section of curly Walnut because it is easy to shape and it’s very warm to the touch.

To accent the selection of timbers, I went with copper tubes for the pinning. A nice 1/8″ from K&S Engineering and a section of 1/4″ OD utility soft grade tubing (for the lanyard hole)

For that extra special touch, I sourced some brass 1/4-20 screws where I would normally use steel. I coupled these with some neoprene washers which would prevent over-tightening since they have a single slot for a screw driver/coin.

After getting all the materials ready to go, it was time to get cracking. First step was to machine the hole for the screws, this is important to do now since the scale would cover this hole up and it’s good to get the messy work done first. A power drill, a 1/4-20 tap and some machine oil made quick work of the threads. The hole was already presized to the correct size so there was no need to drill it out for the tap.

The brass bolts only came in 3/4″ lengths so they were cut and filed down to size. 1/4-20 is a nice, forgiving thread that is strong but small enough to fit into this frame.

Using the threaded holes as a locator, some recesses were drilled into the mating side of the maple JUST in case there was over-tightening. The recess would provide some relief so that the mechanical advantage of the screw wouldn’t delaminate the scale from the core.

Time to adhere the two parts of the back scale into place. The mating surface of the aluinum was keyed with 80 grit sand paper so the epoxy would have something to tack to.

Using pony spring clamps to hold the timber in place. It’s important not to put too much pressure on it since the epoxy wants to squeeze right out if too much is used.

Maker Tip: Get yourself a notepad, a cheap one but with thick paper. Use this combined with a stash of cheap popsicle sticks to mix up your epoxy. When you are done mixing or even if you leave it to set, you can rip off the top sheet of the pad and throw it away. No need for mixing your epoxy on a scrap wood or whatever. You can even drill or punch a hole in it and hang it up near your epoxy supply.

Once the epoxy has had an hour or so to cure, a coping saw it is a great way to remove the excess material. The redheart smells funny when cut and sanded so I wore a dust mask every time I worked with wood. No sense developing a dust allergy.

Now I get to use some of my favourite tools, the Razor File. This particular flavour is a 1/2″ wide, Xfine version. The Razor File actually CUTS the wood instead of abrading it. I work into the core so not to blow out fibres. It’s a good time to note that the laser cut maple was digitally expanded 1mm so the burned edges could be filed away to perfectly meet the aluminum core. The Redheart is filed flush as well.

I am a big fan of power tools as they make quick of work on things but when dealing with special projects and delicate wood, cutting things by hand prevents big mistakes. I love how the slow file process produced a neat pile of light and red coloured filings. Notice the razor file creates chips and not powder.

This is the final shape of the silhouette, the excess epoxy will act as a gap filler mixing with the burned edge of the maple to create very crisp black line.

To clean up the inside slot, a nail file is trimmed down to fit in there and a couple of swipes and it’s done.

Now that the backside scale is profiled, it’s time to prep for the front side scale. Here a 1/8″ bit and a 1/4″ bit are used to clean up the holes, prepping for the copper tubes.

..but before that, the walnut scale needs some attention. Since this is going to be epoxied on before shaping, there are two edges near the exposed aluminum that would be inaccessible after it’s tacked down. I use a pencil crayon to mark where I need to sand back the burned edges.

The frame itself needs to some attention. The exposed aluminum area get a sanding to 600 grit. The smooth transition from wood to aluminum needs to be prefect since there is no other exposed aluminum other than the spine and edges. Having the aluminum smooth there is also important in the gluing process, more on that later.

The copper tubes dry fit into place. They get chucked into a drill and a coarse sanded to create a tooth for the epoxy to grab onto.

Again, spring camps hold down the critical mating areas, mainly the tips and butt end. Some additional epoxy was dabbed onto the tubes so any gaps would be filled.

This is where surface prep proves its worth in time investment. Since the fork tips was sanded flat and smooth, removing any excess epoxy that was squeezed out with a cotton swab was easy and painless. The transition between wood and metal is now seamless with a tiny bead of epoxy filling any gap.

A short while later, I couldn’t help by test fit the bands. These are traditional 5mm wide gum rubber bands that Gaspar sent to me a couple of week ago. They are medium pull and work great with tabs.

You can get a first look of how the tab attachment system works now, the tab is threaded through the frame, and held in with the bolt. Then the tab is rolled over the top and gets held down by the tension of the bands. Upon release, the tab rolls over the frame and like any other OTT shooter, but the bands do not touch the frame, making them last much longer than normal.

After a short trip on the belt sander, the excess surface epoxy, tubes and wood are all flush.

The curly walnut is looking fine.

Returning back to the vice the edges of the walnut where filed back to flush with the frame with a fine, 3/4″ Iwasaki Razor File.

It’s starting to look like a sling!

Time to clean up the aluminum from all the file scratches. A round of 80 grit sand drum with a rotary tool and then a second pass with a 120 grit.

This removes the major scratches and dings.

Now the hardest part. This whole time, it was about prepping the surface for the real artistry: shaping the scales. Normally, a 1/4″ round over bit can be used to just give the whole thing a uniform edge and it would be done. Too easy, too quick, too dangerous and not special enough. Remember, this is going to a champion!

I talk about layout and marking tools in this video:

The marking tools come out, a HB pencil, a white pencil crayon and a compass.

On the walnut, I map out where I want the scale to taper towards the tips so that the thumb can naturally rest and push up against the button head screw. Gaspar holds in his left hand, but to keep things symmetrical, I laid out the taper on both sides. I also mark out the radius on the rest of the handle and the two areas where I want to chamfer and not round (the fork yoke and the butt end)

The back side is even more complicated, I wanted transitions between the radius of the handle and the crisp edge of the slots. The yoke area will have the same chamfer as the walnut side.

Time to get filing. To establish the transition, the Xfine 1/2″ razor file gets plunged into the edge to create the crisp line that follows the frame curve.

Then it was a matter of following the lay out lines and rounding the edge until it met the metal. Taking great care not to cut into the metal surface.

Using a super fine half round file, the roughed out edge is cleaned up to a reasonable smoothness. The goal here is to blend in areas that need blending and leave the crisp edge on the places that need to be left alone. This is where power tools fail and hand finishing and slow methodical cutting wins.

The same technique was applied on the yoke area, establish the crisp transition and then cut away to the guideline. This was a lot easier since a chamfer is much more forgiving than a hand cut radius.

Lather, rinse, repeat on the other side.

The last chamfer is the butt end, I imagined this to be the tip of a broad sword so the two chamfer meet in the middle the two edges of a sword. There is a slight curve but careful filing completes the compound curve.

The back side isn’t quite finished. Since the middle and index fingers get wrapped around the waist area, the scale was filed down with a half round file (so the copper pin could be also filed down simultaneously). The subtle 3mm dip into the surface of the slingshot makes registering the grip a lot easier and intuitive.

Now it was time to pay attention to the walnut/front scale. Blue painters tape is used to cover the aluminum tips to minimize damage if an accidental slip of the file happens. Those who make knives, know this technique all to well to save the highly buffed and prepped surface of a blade.

This was one of the toughest shaping processes since it’s not just a slope, but a compound curve sloping towards the tips and outside of the forks. The goal here was to have a nice place for the thumb to brace since a thumb normally rotates outwards.

Once those two complex slopes were done (super tough to get symmetrical!) The same process of establishing the transition between curve and edge and then continuing to round the edge was done. In the photo is one of my favourite files, a super fine 6″ half round USA made Nicholson.

The file leaves the surface pretty smooth, but some 100 and 240 grit sanding sticks help smooth the transitions and surface out.

A some buffing with a 320 grit sponge to really smooth out the wood.

You can see how the tips of the walnut scale roll out and towards the tip.

Lastly, some synthetic steel wool takes out any remaining weirdness in the surface.

A rubbing alcohol swab removes any grease and dirt (and the redheart tends to deposit on the lighter coloured wood). The compound is quick evaporating so it doesn’t raise any grain, but any grain can be knocked down again with the steel wool.

Finishing!

The whole slingshot gets a 15 min bath in boiled linseed oil and then massage for a couple of minutes. The sling is then left with a thick layer of it for about 30 mins while the the oil has a chance to penetrate the surface.

After the 30 mins, excess is wipe away and again left for another 30 mins.

Meanwhile….the brass screws get chucked into a drill and then while spinning, get pushed into a spinning cloth wheel. The dual spinning action creates a mirror surface in no time. Overkill? Sure. Why not.

You can almost make out my camera!

Shiny!

Time for some Tried & True beeswax/linseed oil mix.

Laying it on thick and then leaving it for 15 mins, wiping away the excess then buffing it dry with a cotton rag. The result is a nice natural finish low shine and smooth texture.

The Maple coupled with the Redheart is just divine, since they are similar in hardness, the texture on both is similar.

One of the best thing about beeswax is that there is no cure time, so onwards to fitting the bands on!

Huge satisfaction in seeing this together.

Once it was together, it was time to get some archivable photos.

Thanks for reading, if you’ve stayed up to this point..it’s time to get up and stretch, I know you’ve sat for at least a fortnight.

Get out and make something.

-Eric

Posted on August 3, 2014August 3, 2014 by Metro Grade Goods — Leave a comment

Metro Made | Oak Metbro Unishot and Classic

Since the launch of the new Metbro line, they have garnered a small following of slingers wanting to try out the old school feel but with some modern aesthetics. This Metro Made is about finishing a pair of Metbros, a Classic and a Unishot with some old growth oak, brass pins and a leather insert for the thumb pad.

Want to make one? Check out our Maker category.

Metro Grade Goods Maker Category

Posted on May 31, 2014May 31, 2014 by Metro Grade Goods — 1 Comment

Metro Made | Wasply PFS Slingshot

Been a little while since I’ve posted a Metro Made, so there is no reason why NOT to post one. Fresh from the laser cutter to your workshop, this is a tutorial on how to assemble and finish your Wasply PFS Maker Kit. Don’t have one? You can get yours here: Wasply PFS Maker Kit

In the kit, you’ll have two cores, and two sets of palm swells.

First things first, glue up the core, and two palm swells.

When they are set up, I used a belt sander to start to shape the palm swells. This make life a lot easier later if you take off the bulk of the material first.

Once the swells are partial shaped, time to glue up the swells on the body core.

I used a spindle sander to remove the laser burned wood but this can be done with files and sandpaper.

A round file expands and refines the band grooves.

A few more swipes with a first cut file and the inside of the forks is cleaned up.

The hardest part of the build is shaping the palm swells so they are perfectly round. I used the belt sander again, rotating it like a drum stick. Rasps, files and sandpaper will do the same job.

Using some 100 grit nail files, the palm swell is blended into the core, making a seamless joint.

An optional machining step is to cut some scallops with a big 3″ drum into the finger grip area, but this can be done with a 1/2″ round file.

Now to finish it! A variety of 100 grit, 320 grit foam blocks and a final swipe with some steel wool to prep the surface for clear coat or oil.

The one on the left is one designed by Magpie Slingshots and I replicated it to test out the scale. We worked in collaboration to come to the final design of the Wasply PFS.

After a couple of coats of clear and some light buffing with the wool to get it a more matte finish, the Wasply PFS is done!

Thanks for reading and in case you missed it, you can get your Wasply PFS Maker kit at our store.

Posted on May 5, 2014May 13, 2014 by Metro Grade Goods — Leave a comment

Metro Made | The Turkey Shuckpow!

Shops that have skunkworks devisions will always try new things, one offs, tests and prototypes that often lead to very possible production ideas. In this ‘skunkworks’ post, I try to do a few things differently that will definitely make its way into some production slingshots.

It’s much easier to test something when you have a solid frame to work on, quite literally. I took our SHUCKAPOW design and made up a 1/4″ Baltic Birch plywood core. From there, it was some quick work since the spacer veneers in between the layers would curl from the wet glue moisture. I have a lot of smaller pieces of exotic and hardwood veneers and it would take a life time of making slings to use them as small spacers between surface laminations, so I decided to try something new, skunkworks test #1: surface veneer lamination.

On top of the ply core, a layer of purple heart was laminated to both sides. This was left to try a bit before sanding down the surface.

In between the Paduak layers, I laser cut some maple veneer to contrast between the orange and purple. Again, left to set up a bit before sanding the face flat to receive the veneer.

This is the entire sandwich. On one side is a layer of cherry/zebrawood veneer and on the other side birch/wenge. Two scrap plywood boards kept everything tight and under pressure. I actually leave this for a whole day to ensure a good bond between the veneer and woods.

It’s a bit of a mess, but the careful planning and forethought will pay off in the end.

After curing, it was time to try skunkworks test 2: differential layer laser etching of the veneer. Using the laser set at a 20% higher power than usual, I try to vaporize the zebra wood to reveal the cherry underneath. Check!

Worked very well. I also want to note that I purposely used a more watery wood glue to bond the two veneers together to ensure that the layers are well set.

I do the same to the other side, but the Wenge is much harder than the Zebrawood, so there is only a different in texture and not colour. It is at this point I take the sling to the belt/disc sander and clean up the edges, revealing the sweet, sweet colour palette.

The spindle sander takes care of the rest of the burned edges and the insane amount of lay up work is showing it’s true “colours”.

This is where a bit of experience comes in handy. Having made many slingshots with plywood before, I knew that underlying layers would show up once the edge was routed. A rim of orange surrounds the dark hardwood veneers, making me very pleased with the progress. The top two layers of light wood plus darkwood makes for a very clean and graphic contrast.

Skunkworks test #1: scalloped grip areas. I have seen this done on many beautiful slingshots from other makers, but I couldn’t figure out how to do it correctly until now. I finally figured out that if I took the biggest drum on the spindle sander, I could use the top layer as a guide as to how much to remove and the general angle of contacting the drum. The existing curve helped guide the process along and the 100 grit drum took off material in a hurry. Before this step, I drilled out the tube holes and counter sunk them too.

After all the major machining steps, it was time to give the Turkey Shuckapow the full sanding treatment. 100, 240, 600 and steel wool, the off to the paint booth for three coats of acrylic. The clear coat really brings out that differential veneer etching, the cherry shining through the zebra wood.

The Wenge side is much more subtle, but the whole point is use this as a test bed for some previously unused techniques.

After some cure time in front of fan, I quickly wipe it with some steel wool to take off some of the glare. Then it’s time for a close up!

You are probably thinking…why did I name is the Turkey Shukapow? Because in the end, the colour, the shape, the lines, reminded me of a vintage 50’s bowling alley. What’s better than three strikes in a row? 10 dead centre shots with a custom slingshot.

Thanks for reading yet another long winded post…were you interested in HAVING it? Buy the Turkey Shuckapow here!

-Stay True-

-Eric

Posted on April 27, 2014May 6, 2014 by Metro Grade Goods — 4 Comments

Metro Made | Flatland Flame

When I was commissioned by Prairie Fire magazine to make a few slingshots for their annual fundraiser, I gladly accepted the challenge. This Metro Made documents the creation of the first of the two, the Flatland Flame.

I started with a familiar design, the Harlequin Capuchin. Laser cut some 1/16″ thick purple heart slabs. Since the piece of purple heart I had was only 3″ wide, I had to split it up in halves.

To get a bit more contrast between the purple heart and laminated faces, some maple veneer was also cut.

Slowly, but surely, each piece of the puzzle was cut from various woods. Shown here is some Cocobolo, some Padauk and some Tulipwood.

On the back side is Rock Maple and Padauk. To complete the main face, Chakte-Kok, Bloodwood, Yellow Heart and a maple circle.

Now, the longest and hardest part of the build, the lay up. To start, the Purple Heart halves are glued to the plywood frame with some maple spacers.

After about 15 minutes of compression, the veneer is sanded flat, ready to accept the next step.

The maple veneer spacer to complete the layer. This was repeated on the other side to mirror the wood pattern.

Like the original Harlequin Capuchin, I started with the simpler back side because it take less time to setup and dry. Zebrawood and Wenge spacers make a nice texture between the contrasting woods.

Finally laying up the last pieces of the back side, spaced by Ebony and more maple. Slightly less than 30 minutes later, the face was sanded flat and it was onto the main face.

It’s messy, but it’s the way it has to be….

Another 30 minutes later, the face was ready to be flushed. Before more sanding, I moved back to the laser cutter to etch in some markings.

The Metro Made Skullthulu getting etched into the maple circle.

Flipping it over, the name of the sling etched.

Cleaning up the edges from the laser cut burning and refining the shape a bit.

To relieve some pressure on the final round over, all the edges where taken down with a 1/8″ bit.

Like the Mesquito Supernatural, select edges are taken down with the 1/4″ bit.

Sanding…lots of it. 100 grit nail file, 150 grit foam block, 240 foam block, 600 grit paper and a buffing with 000 steel wool. It’s the smoothest I’ve ever gotten wood to be.

2 coats of acrylic sealer and I washed my hands of this project.

The incredibly smooth surface thanks to the steel wool provided a perfect substrate for the sealer, the photos don’t lie.

Yet another satisfying job done.

-Stay True-

Eric

Posted on April 19, 2014May 6, 2014 by Metro Grade Goods — Leave a comment

Metro Made | The Dark Horse

Sometimes, a nice long, complicated project is all you need to really get over your creative slump. Carefully calculating how things go together, taking the time to properly do clamp things down and lovingly polishing your new creation, it’s all in the details.

The Dark Horse is exactly that.

After doing some tests, all the dark woods that I had selected for this project absorbed too much heat to be cut so the result was a very burnt and singed edge and surface. So, switching to manual navigation!

I could at least start with a couple of cores and and a back side scale. This time around, a 1/4″ slab of purple heart, a 1/4″ slab of American Walnut and a back side scale of Black Walnut. The walnut laser cuts and etches nicely so the name Dark Horse and the MGG skull was etched on it prior to assembly.

After the cores where cut, it was time to lay up the bits of wood. Tackling this like a Tetris game, sanding slowly to fit the blocks into place, delineating the layers with a triple stacking of contrasting veneers (maple, ebony, maple). The inside core is American Walnut, which is much lighter than the Black Walnut used for the backside.

Always choose a hard wood for the fork tips in case of a fork hit, in this case, Zircote. It has a VERY interesting micro texture and is hard as nails. Sandwiched in the middle and will eventually make the scoop of the yoke, is Zebrawood. Below that is the aforementioned triple stacked veneer. In the center is rectangle of Wenge (this was purposeful), the Wenge is flanked by Black Palm end grain and some more of the American Walnut.

After gluing up the final bits, Black Palm and Pau Ferro for the pinky hole, the excess was cut off with the band saw. The whole face was then flush sanded to reveal the nice geometric dark wood pattern.

Once that was done, it was time to trim up the new hardwood face so that it conformed to the shape of the rest of the body. Using a 1/4″ flush router bit, the final trim was quick and easy because I built the pattern on a laser cut blank. I’ll make note here that going at a steady pace is more important than speeding through the pass on the router, hardwoods chip really easily.

After laminating the cores to the new trimmed face, the hole for the tubes needed to be drilled. 3/4″ of existing hole as guide made locating the holes pretty easy.

Moving over to the spindle sander to clean up the laser marks on the sides of the Purple Heart, American Walnut and Black Walnut cores. The Zircote is already showing its amazing stepped grain.

Switching bits to a 1/4″ round over, select edges were taken down, mainly the parts where the hand hits. The Black Palm is now showing its very unique, vascular bundle texture. The Pau Ferro (on the pinky hole) is also showing it’s wide, dark streaky grain. The other edges were knocked down with a 1/8″ round over bit but no photos were taken of that process.

I wrote before that the Wenge was placed in the heart of the face for a reason. Wenge is exceptionally hard but it also has a differential density between the grains. This means each vein of wood will react differently to laser etching, aka heat. Knowing and understanding this material property, I scaled a knight chess piece vector to be etched into the Wenge. The etching gave a pleasing wavy texture to the graphic and the outcome was as expected, a textural difference between the wood’s sanded surface and the etching. This would be further enhanced when the polish is applied.

Despite taking precautions and a steady hand, there was still some chipping that occurred at the wood’s mating joints. Some ghetto wood filler, glue and saw dust, filled those gaps easily and blended back into the wood work.

I took extra care in sanding and prepping the surface to accept the acrylic spray, going from 100 git foam blocks, to 240 grit nail files to 600 grit paper all the way to 1000 grit strips. Then it was off to paint, 4 coats of spray with a light buffing in between to smooth out the overspray marks. If you look closely, you can see the laser etching detail is much more clear once the clear coat hit it, the ridges of the etch, surrounded by the smooth surface.

45 minutes later, the coating is now ready for a polish using my super secret sauce, the nail buffer. A 4 step foam block backed with progressive grits, close to 10,000 grit in roughness rating.

A couple of minutes of buffing and its off to the photoshop!

Thanks for reading!

Had enough? Want to buy this slingshot? Get it here: Dark Horse Capuchin Slingshot

-Eric

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Posted on December 8, 2013December 15, 2013 by Metro Grade Goods — Leave a comment

Metro Grade Tuff Udder Pouches

When building custom slingshots, there three key areas of focus, the frame, the bands and the pouch. The last one often overlooked but it’s one of the most important parts of the slingshot.

We’d like to introduce the first Metro Grade Tuff Udder pouch: The Big Bertha.

Holding the ammo correctly, catapulting it forward, retaining its shape, these are all features of a good ammo pouch design.

Here’s a quick video of the pouches:

We started with a 1/8″ thick, heavily oiled cow hide and threw it under the laser cutter. The design features a ventilated body for increased speed and reduced weight. A middle hole centers the ammo perfectly for consistent results shot after shot.

The laser cutting left the surface dirty, marred with soot and residue. Since we wanted to wash these pouches with a light detergent to remove the surface oil, the bath also removed the grim.

We wanted to start out Tuff Udder series with the biggest and most versatile one, allowing the slinger to shoot anything from 1/4″ steel balls to big rocks found in the wild.

Just under 3″, the Big Bertha isn’t a small pouch, so it’s ideal for heavier band sets.

Posted on November 21, 2013May 6, 2014 by Metro Grade Goods — 3 Comments

Metro Made | Video – Plexiglass Capuchin Slingshot

Acrylic Plexiglass is one of materials that has so many uses and finishes that it’s hard to miss when used correctly.

Often mistaken for polycarbonate (Lexan), Plexiglas isn’t the bullet proof plastic, it’s the hard, semi strong material that can be made completely clear again after being machined. Unlike Polycarbonate plastic, acrylic CAN be cut with a laser, which is how what we used to cut the outside profile of this slingshot.

How’d we do it? It’ll all become clear very soon…..

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Want this slingshot? WIN IT!

Go to the Metro Grade Facebook Group : Here

Like, comment and share the post about the video. When we reach 300 likes, we’ll pick a random winner from that comment list and give this away!