Thread tapping

[johndib]

I'm tapping 14mmx1.25 holes in aluminum. Using an er32 tap holder and a 7/16" collet but the tap slips in the collet. Obviously have it tight. Is there a better/different tap holder? Or a different way to lock the tap in the collet? Or? Tapping at 150 rpm and a feed rate of 3.9. Haven't tried different speeds or feeds but not sure that would make a difference.

 

[tof1]

You're using a ER tap collet that grips the square tap end and it's still slipping?

 

[gregormarwick]

I'm tapping 14mmx1.25 holes in aluminum. Using an er32 tap holder and a 7/16" collet but the tap slips in the collet. Obviously have it tight. Is there a better/different tap holder? Or a different way to lock the tap in the collet? Or? Tapping at 150 rpm and a feed rate of 3.9. Haven't tried different speeds or feeds but not sure that would make a difference.

3.9 what? inches per minute? If so that's completely wrong. Correct feed @ 150rpm is 7.382 ipm. Are you rigid tapping or using a tension-compression holder?

If you were rigid tapping with that tap and that feed and speed in aluminium I'd entirely expect you to just drill a 14mm hole, rather than have the tap slip in the collet, although the tap could pull out of the collet if it's not actually tight.

However, if you're using a tension-compression holder then it will likely tap in so far, until the tapping chuck hits max. tension and then the tap will start pulling out of the collet.

 

[Larry Dickman]

your federate is so far off it's unbelievable. 1st, 14mm in aluminum, 500 rpm would be conservative. Then your feed s/b 24.6. Give that a try.

 

[johndib]

You're using a ER tap collet that grips the square tap end and it's still slipping?

Round collet. Where do I get an er32 collet that will grip the square of a tap?

 

[Hazzert]

Fix your federate first or you'll be buying a new tap right after the holder.

1.25/25.4 X RPM= feedrate for a metric tap

 

[tof1]

Round collet. Where do I get an er32 collet that will grip the square of a tap?

Tap Collets | MSCDirect.com

 

[johndib]

Got it. Thanks but I think whoever said I had the Feed rate wrong was... right. Fixed that and it seemed to tap correct without the tap slipping. Thank you all.

 

[Red James]

This is a perfect example of the benefit of programing feed per revolution (G95 on most machines). The feed per rev is the pitch of the tap, and is independent of the RPM.