Threading Acetal

[DareBee]

I am looking at a job requiring tapped holes in Acetal.
Does anyone know if there are taps specifically made with extra clearance or what not for tapping plastics?
If so how about manufacture names and or supplier links.

[cadman]

Most of the major tap manufacturers make taps that are oversize +.003/.005 specifically for threaded holes that will get thick plating. I had a job that needed oversize threads and I used Besley and Sossner oversize taps for this job.
I used to machine a lot of Delrin & Acetal and I just used coated high performance spiral flute taps for aluminum. There would be an occasional loose thread, but overall these worked good.

CM

[Geof]

For Delrin (acetal) I use standard spiral flute taps that have never touched anything but Delrin. Use plenty of coolant and you can run at aluminum speeds. Two cautions are: 1, if you are dealing with black Delrin your taps will only do a few hundred holes because the black is abrasive. 2, make sure the flutes on the tap are cleared between holes otherwise you might find you are trying to ram a blob of melted and re-hardened acetal down your hole.

If you are tapping you must be drilling; make sure your drills are also sharp and keep the speed moderate and feed up with plenty of coolant and pecks about 1/2 drill diameter. Acetal will melt very readily inside deep holes.

[DareBee]

Thanks Guys
Geof the spiral flute taps will clog easier than a spiral point, the main hole I am looking at is a through hole approx 1.5x dia.
Would you still use SF instead of SP?
IMO the SF have a touch more positive shear action but are weaker and harder to clean.

[Geof]

I should have mentioned the spiral flute is for blind holes. Yes on a through hole the spiral point does not clog because the chip gets cleaned during retraction.

[DareBee]

Thanks
I wasn't trying to debate the use of SP over SF taps was just wondering if there was an un-obvious reason to use the SF due to the specifics of Acetal (Delrin) ;-)
It's all good