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Teflon Tapping

D

darthhippy

Plastic
Joined
Oct 20, 2021
I need to drill a 24mm diameter by 40 degree tapper plug about 3 inches long. (my lab works and mixes both imperial and metric cause what is convience?)

The first step would be put the plug in a 3 jaw chuck and use the tailstock to drill out a 25/64 whol with the 25/64 drill bit.

the tricky part comes with tapping the hole with a hand tap. Is a hand tap gentle enough for this operation or should I use a form tap?
 
The most difficult thing about machining teflon is how squishy and slippery it is. I would not try form tapping, only cut taps. We machine teflon every once in a while and I hate every second of it. Delrin is much easier due to the higher hardness.
 
Max speaks the truth.

Be sure to support (if possible) the outside of your project. The tap will simply push the matl out of the way if it can.

Oh, and dead sharp tooling is utmost here. (no old crappy taps......got it?)
 
MaxPrairie said:
It could, maybe run the tap in then freezer then run the tap in again. Helps to machine rubber quite a bit...
Click to expand...

Thanks for all the feedback. I won't have time to do it today. The moment I can get away from production tmrw I will start. Ill throw the tap in the freezer when I arrive and by 11 or 12 I should have it all drilled out and ready.
 
Make sure your tools have only cut Teflon or they are brand new. Use plastic or aluminum specific tools and a high hook tap if tapping. Other than that it's not bad to machine, much easier than polyethylene. No forming and don't waste your time trying to freeze it. Something like this would be simple on a cnc mill where you can threadmill it. I used to machine thousands of little intricate parts out of Teflon and never found it difficult, as long as you can hold onto it.
 
I think the recommendation was to put the part in the freezer- not the tap. Also, don't even try a form tap, Teflon is way too soft for a form tap to work.
 
Seems like this is a time to call a tap manufacturer like Emuge. My intuition is that you need a custom tap with high rake angle on the cutting edges maybe skipped-tooth pattern deeper flutes etc. They may also have formulas for making the a .250 custom tap to .265, for example. You can't be the only guy to need to do this.

Denis
 
MaxPrairie said:
The most difficult thing about machining teflon is how squishy and slippery it is.
Click to expand...

I'd rather machine Teflon than UHMW any day of the week lol.

Other than that Teflon isn't bad, it cuts really nice. But like others have said, it's not Delrin which is a dream.
 
I've posted this here before, but here it goes again. Teflon has some distinct phases, and the bitch of machining it (to an accurate dimension) comes from the CTE being distinct for each of those phases.

tma1.jpg

Don't worry about freezing it, just keep it OUT of that wonky crystalline hexagonal phase IV. Ya know, the one that goes from about room temperature ±10°C on the chart. Tg is way up at 150°C+ so freezing it won't do you any favors on that front, but it'll thermally move like crazy right around room temp.
 
DavidScott said:
Make sure your tools have only cut Teflon or they are brand new. Use plastic or aluminum specific tools and a high hook tap if tapping. Other than that it's not bad to machine, much easier than polyethylene. No forming and don't waste your time trying to freeze it. Something like this would be simple on a cnc mill where you can threadmill it. I used to machine thousands of little intricate parts out of Teflon and never found it difficult, as long as you can hold onto it.
Click to expand...

I think this had to be in the beginning of your post :)

my experience is not production, but sometimes I need to repair or modify scientific tools, never had a problem tapping it, even if the tap isn't brand new (or a special for plastic), the thread will still form enough for the screw to screw in, if it is slightly undersized, the screw will displace the material around it (this is with M10 and smaller, haven't had the need to do larger threads)

that being said - I throw taps as soon as I notice a problem with them, so my "not new" taps are still quite sharp

have a project on the table right now where I need to drill few 0.7mm holes 14mm deep in teflon to fit some pogo pins
 
I was the first person to use that particular tap so it was fresh and sharp. Used some soft jaw bench vice and a got the tap run straight and true after a little start with the tail stock. Used a fresh 25/64 drill bit in the tail-stock for the thru hole. The plug goes straight in gets nice and snug. It's gonna work just fine for the bromine pump on the barrel bung. The most annoying part was making sure to break the chips and clear the flutes. Had to use some tweezers to pull the last little bits of the tapping chips.
 
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