Designing a Fast, Lightweight Speed Square Holder using 3D printing

As a mechanical engineer and product designer, I'm always looking for ways to make great tool holders even better. Before I became an engineer I spent years in the construction trades, doing wiring, framing, mechanical, plumbing, sheetrock, and I even spent some time building high-end yachts! 

More often than not I find myself working in the shop or on a jobsite with my tools scattered around me as I move around. I love the idea of big toolbags (and even own an amazing set of Occidental framer's bags) but it's really rare that I ever actually wear them. Face it: for most jobs you need a couple essential tools at arm's reach. Most of them, like a nail gun or worm-drive saw, you don't really want to carry around. But a few are indispensable.

Enter one of my favorite tools: the humble Speed Square. This is a tool that does so many jobs it's hard to count them all.

• Use it as a guide for straight skilsaw cuts on 2X lumber.
• It's the perfect tool for stair layout.
• Measure angles quickly and easily.
• Add a spring clamp to the T side and it becomes a temporary brace for butt joints.
• Open a cold one after work. 

The awesome and incredibly useful Swanson (or pick your brand) Speed Square

The speed square is truly one of those tools I can't be without. The problem is it's really hard to carry around. Often I'll strap on my big framer's bags just so that I have a big enough pocket to fit my speed square. 

I'd been mulling over how to build a holder or holster for this square for a long time, but I was struggling to find a design that was clever, minimal, and would hold up to some real abuse. I considered a big hook, or a little stainless steel bracket similar to my TapeMaster. But every design had a different problem: too bulky, not secure enough, difficult to use, etc. Then late one night I ran across a video of This Old House that had my solution!

(BTW that's a great video if you want to learn more about how to use a speed square.)

This "slot" design was just what I was looking for, but I wanted to make something that would be more tactical - because as one of my customers says, "tactical is practical"...

So I opened up Fusion360, warmed up my 3D printer, and started tinkering. First I started with an easy-printing plastic called PLA and a really basic design. That's the design you see in the top-left of the picture below. It's one, really big piece and it's approximately the same size as Tom Silva's holder in the video. It actually worked pretty well, but I felt like I could make the design much lower profile. My other holsters tend to disappear when there isn't a tool in them, so I set that as my goal.

Just a bit of the huge pile of printed test pieces. I won't stop until I make a holster that stands up against Kydex!

I started to carve away the excess material in CAD, being careful that the design would still print well. The key is to be sure there are no overhangs and that the wall thicknesses are basically all the same. I use a slicer called Simplify3D and I've found that if I use just the right settings I can get a thin wall to be completely filled with plastic. Combined with a heated chamber and some exotic materials like polycarbonate and PETG I can achieve printed parts that are similar in strength to injection molded ones. That's a big deal because it means I can use designs that are much more complex and functional than typical simple Kydex-formed holsters without having to invest thousand's of dollars into injection molds.

In my career as a mechanical engineer, I've printed probably over $100K in 3D stuff on pretty much every printer out there. The way these machines are now, I'm just blown away at how good these prints are.

The resulting holster is truly a thing of beauty. I settled on carbon-filled PETG for the main body and friction finger. It's tough, very rigid, and just looks tacti-cool. The clip needs some extra toughness since it needs to flex on and off a belt all it's life and stand up to getting wrenched around in weird ways when you forget to take it off getting in your truck. It's made of a polycarbonate (think bullet-proof glass) and ABS blend. Without further ado, here are some shots of the finished design!

The finished design. Much lower profile and looks really cool. There is a big opening at the top to provide an easy target so putting the square back in takes less aim and you can do it without looking.

Here you can see the tension finger. That gives it a really nice positive friction that keeps it from sliding out or rattling around, but it comes out easily when pulled.

The clip can be swapped to either side so the holder can be worn on whatever side of your belt you find most convenient. The clip can fit belts up to 2" so it can go on your normal pants belt or your work bags.

Because of the custom design, I couldn't use the normal FOMI clip used on Holstery products. I also wanted something a bit longer to fit on 2" tool belts. Here's a quick comparison to show how strong the PC-ABS 3D printed clips are. Compared to the injection-molded clips we use it's basically the same strength.

It's been a long, but really fun road getting here. I've printed nearly 100 different prototypes getting to a final design. I think people are really going to love this holster and I'm excited to apply what I've learned about materials, 3D printing optimization, and design to a whole new series of holsters in the future.

Stay tuned!

***UPDATE***

Well the 3D printing experiment has come to a close. I really liked building these but unfortunately they were just not quite as strong as they needed to be to hold up to the rigors of the job site.

Instead, I'm replacing this with an aluminum version with the same dimensions. For anyone who has one of the plastic versions and would like a replacement, I'm offering that free-of-charge. Just shoot me an email with a pic of your holster and I'll get one on it's way to you.