Threading acrylic for a machine bolt

While the acrylic is still warm and soft from the laser, you can thread a cut hole by simply driving a bolt into it.

Plastic threads aren’t durable, especially for steel bolts, and created so crudely. But it seems quite secure enough for my purpose (a fixture for a wood project).

The acrylic was 1/4" Proofgrade. The screw was a #20 1/4" stainless steel bolt which measured 0.24" on the outside of the threads. I cut a hole of nominal width 0.225".


Handy to know! I suspect you could also do this by warming the hole with a heat gun before threading the bolt.


Yes, I originally read the advice to use a heat gun, and not having one, thought I’d try this instead.

If it’s not warm enough, it’ll crack. (I tried.) It probably helped that there were cuts in the surrounding area too, making it warmer, and that the acrylic was thick (1/4", not 1/8").


Those can often crack even if done appropriately warm. I’ve generally use heated brass threaded inserts which work great. Then you have metal on metal and can be extremely strong, and when I needed an alternative I engraved a nut pocket on the back and used a clearance hole if possible.

for example for the inserts:

the tool (although regular solder iron tips work in a pinch):


Acrylic taps just fine with a sharp tap. Not one that’s been used on other materials.


I have used a tap (for much smaller ~m3 screws) on acrylic without heating and, have had no problems with cracking.


I agree that what I did is the least reliable option, to be used only when nothing else is at hand and it suffices for the task.

Thanks for the link (“heated brass threaded inserts”), haven’t heard of those before. I happen to have some steel threaded wood inserts, which might work, but with the large threads, I’d probably need the heat gun.

A tap kit sounds great, but is the least cheap option if you don’t already have one.

The nut pocket is a good option (or just attaching the nut with epoxy) … but I was out of nuts too!

A clip nut can work in some cases, or maybe an expansion nut (well nut).


we exist in somewhat comical world, where the backup plan for a $0.25 nut is a $4000 laser cutter… :thinking:


Those inserts are great for 3D printing too, BTW. I’ve never bothered buying the tool, they push right in with a soldering iron.


Yeah, It’s a smidge easier to keep them perfectly square with the tips designed for them, but have certainly just used the regular tip on my iron. For folks using these, remember you soldering iron is probably set to a much higher temperature than the thermoplastic you are inserting into, and depending on the material can really bake the plastic making it brittle. If your soldering iron doesn’t have a settable temperature just use it as quickly as possible to keep heating to a minimum


I wonder if anyone makes a TS100/Pinecil style tip designed for inserting these. That would be super handy.

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