Open-Source Extruded Profile systems are a mature breed these days. With Openbuilds, Makerslide, and Openbeam, we’ve got plenty of systems to choose from; and Amazon and Alibaba are coming in strong with lots of generic interchangeable parts. These open-source framing systems have borrowed tricks from some decades-old industry players like Rexroth and 80/20. But from all they’ve gleaned, there’s still one trick they haven’t snagged yet: affordable springloaded T-nuts.
I’ve discussed a few tricks when working with these systems before, and Roger Cheng came up with a 3D printed technique for working with T-nuts. But today I’ll take another step and show you how to make our own springs for VSlot rail nuts.
Why Springload in the First Place?
For anyone playing extrusion hot-potato in a multi-person build a-la Lasersaur, springloaded T-Nuts are a wonderful convenience. When springloaded, these otherwise normal T-nuts stick in place rather than slide down the slot, making the building process more manageable with less parts to track simultaneously. We just set and forget!
Don’t get me wrong. Springloaded T-nuts already exist for us hobbyists using maker-style extrusions. But they’re pricey, as in more-than-a-dollar-a-pop pricey. Alternatively, we have the more popular “afterthought nuts,” commonly known as “Drop-In” style T-nuts. We can conveniently add these nuts even after we’ve closed off access to the slides with other nuts. But anyone who’s done that a few dozen times knows two things. First, orienting a panel full of these nuts can be cumbersome, and second: drop-in T-nuts don’t always seat properly when tightened, leaving them catching nothing and utterly useless.
In short, springloading the vanilla T-nut with our own springs is the cheapest bet for reliable assembly that guarantees that our nuts stay fixed during assembly, if you can sacrifice an hour to make the springs.
Ok; enough with the chit-chat. Let’s start making springs!
For this build, you’ll need:
- 1x M6 threaded rod with 1mm pitch or a 30+mm M6 screw of any type
- 1x hand drill
- 1x set of needle-nose pliers (normal-nose pliers work too.)
- 1x set of hard wire cutters (such as McMaster-Carr PN: 59445A45)
- 1x spool of 0.016-in. stainless steel wire (McMaster-Carr PN: 949K59)
- 1x safety glasses per pair of eyeballs
I’ll make two forewarnings.
First, this stainless wire is fairly thin stuff. I’m sure you can substitute other wire types, but if you use anything thicker you must wear gloves. The wire I chose happens to be thin enough that it’s fairly friendly to form without the risk of drawing blood.
Second, this stainless wire is also much harder than copper hookup wire. In fact, it’ll gladly nom your electronics wire cutters if you let them get too close to each other. I know it’s tempting, but make sure you use wire cutters that can handle hard wire, and, for heaven’s sake, don’t put this stuff anywhere near your teeth!
Heads-up: plop on some eye-protection before marching into these instructions in real life!
To prevent the wire from popping out of the drill chuck, we need to fatten up the tip. With pliers, curl away the end into a small lump like shown.
From here, put a right-angle bend about 16mm (0.629in.) down the length. This bent piece will serve as our “key” for loading into the chuck. Now, unspool about 450mm (1.5ft) of wire and chop it off with your hard wire cutters.
Now, let’s prep the tool. Load a small portion of your M6 threaded rod (or really long screw) into your hand drill’s chuck. Here I’m using a 40mm, M6 set screw with 5 threads-worth inserted in the chuck.
If your drill has a low-speed mode, set it now. This next part is counter-intuitive: set your drill to the unscrew setting (aka: counterclockwise), which will make the wire climb the screw thread. From there, load the bent tip of the wire into the free space between the drill chuck teeth like shown.
Slowly engage the drill trigger and let the wire collect on the screw. Rest your left-hand index finger on the wire such that it rests on a screw groove and slowly spool up the wire with the drill trigger.
As it spools, keep your thumb away from resting directly on the wire. It’s tempting to rest our thumb on top of the wire and close to the screw, but it’s a pinch point.
As you continue spooling do not spool up the whole wire length. It’s easy to lose control and have it whip your fingers. Larger wires would be sure to cut your hand, but this one would still leave a nasty sting.
Instead, stop spooling with about 30mm (1.2in) of loose wire left. From there, remove your spooling hand, and the wire should uncoil itself with no pain to those precious fingers. Ta-daa! Your first spring has come to life.
Note: Notice how our spring tends to expand after we finish winding it? I’ve tried a few different screw types and finally landed on M6, which leaves the spring expanding to a size that just perfectly fits over the bottom of a classic VSlot T-nut.
At this point, our spring is a bit squished, so give it a stretch to give our spring about a 2mm pitch. I begrudgingly put a number on this step because I do this part by feel, and I’d encourage you to do the same. The stainless steel has such a weak spring constant that tolerances on this step are very forgiving.
Finally, give that spring a haircut. With your hard wire cutters, cut down smaller springs that have about 3 wraps apiece. Again, tolerances in this step are also forgiving. If your spring has between 2.5 and 3.5 wraps, it’ll work. Remember: the whole idea behind these pieces is to save time later, not spend time now, right?
Finally, we’ve made it to that glorious moment! Load a spring on the back of your T-nut, slide it victoriously into position, and simply beam with exultation. And, perhaps, post to the internet. Tag appropriately. Call mom.
This process may be a bit time-consuming, but I find it rather therapeutic when I’m supposed to be writing research papers. And for all the times where I have extrusions mounted vertically, these springs are a huge win.