??'s about Acetal Plastic Machining (Delrin)

[Davefr]

I need to mount some small brackets on a piece of Acetal plastic that's .25" thick.

The screws will probably be 8-32 or 10-24 X 3/8".

Does .25" thick Acetal tap well? Does it have reasonable screw holding ability at that thickness? (I need very little strength).

Anyone have experience with Acetal plastics?

TIA

 

[EdT]

IMHO, that should work fine. If it was me I think I would opt for the finer threads. Use sharp tap that will actually cut the material rather than just deforming it although as far as screw retention that might be a plus.

 

[jeffg]

I have good luck with freezing the material before tapping. The holes dont shrink up as much.

What kind of force will the brackets have to hold? If its too much for the threads to hold, you might try some threaded inserts that go in from the back and have a flange to prevent pull through.

 

[gsloan]

I have machined many parts from Acetal. It is one of the easiest materials to cut and is very stable. You will have no trouble tapping. The only thing I would warn you about is if it will be used outdoors or will be exposed to much UV light, the white or natural will deteriorate fairly soon but the black has UV protection.

 

[bmk]

I machine Delrin quite a bit. Use the 10-24 tap with a #25 tap drill. No need to freeze it prior. I wouldn't power tap it though. JMT

 

[matt_i]

Also have machined a fair amount of acetal (Delrin) always at room temp. Sharp tools, dont go uber fast just because its a "soft" material as you do not want to melt it.

I would also recommend the #10-24 with a coarser thread.

 

[A_Pmech]

Use a new and sharp spiral point tap, coarse thread and zap it through with a hand drill.

If necessary, a small amount of vegetable oil as a lubricant. Like most "machinable" engineering plastics, it machines amazingly well.