Can I start a thread with a plug tap?

[martik777]

1/4-28 LH - no taper taps available this week. 7/32" hole.

What can I do to start the tap easily?

 

[T Bredehoft]

Hold the tap in a drill press, secure the hole immediately below it, (secure the material the hole is in) DO NOT START THE DRILL PRESS, UNPLUG IT. Lower the tap into the hole and turn it by hand, or with a pipe wrench if necessary, but DO NOT USE THE MOTOR,

 

[Ischgl99]

All I use are plug and bottoming taps, just put a bit of a chamfer on the hole and it should go in no problem.

 

[martik777]

Hold the tap in a drill press, secure the hole immediately below it, (secure the material the hole is in) DO NOT START THE DRILL PRESS, UNPLUG IT. Lower the tap into the hole and turn it by hand, or with a pipe wrench if necessary, but DO NOT USE THE MOTOR,

I just tapped ~50 parts (1018 1/4" deep thru hole) , no issues, on the mill under power (jogging) then the tap broke. I noticed it slipping on the last couple parts so tightened the belt which is likely what caused it to break. Not sure why it was harder to tap maybe the tap was getting dull?
Anyways will use your advise and tap the rest by hand but it is hard to get a feel rotating the pulley on the top of the mill by hand.

 

[aliva]

I've ground off the first couple of threads on the tap, now you have a starter tap. I've done the same with reamers

 

[mickri]

I added an extension to one of my tap wrenches so it stays centered in a chuck. I turn it by hand. Have never tried power taping. Too afraid that I will break the tap.

 

[Eddyde]

Yes you can tap with a plug tap, done it many times even under power, low speed 100 rpm on the mill.

 

[martik777]

Yes you can tap with a plug tap, done it many times even under power, low speed 100 rpm on the mill.

Power tap using jog mode (<30rpm) worked great for 50 pieces but then the tap started slipping in the collet I tightened the belt then it broke. Any idea why? Tap was uses for maybe 200 pcs total (1018 1/4" depth thru hole)

 

[benmychree]

Power tap using jog mode (<30rpm) worked great for 50 pieces but then the tap started slipping in the collet I tightened the belt then it broke. Any idea why? Tap was uses for maybe 200 pcs total (1018 1/4" depth thru hole)

Tapa get dull ! Then they break ---

 

[benmychree]

I use plug taps for power and hand tapping routinely, always have, very seldom use taper taps, which in my experience have a lot more drag than plug taps. I have a Weldon tap sharpening attachment for my cutter grinder, so, can salvage dull and broken taps.