Thread: Hole tapping

If there had been slag you should of noticed it when you drilled the taping hole.
Was the tap square to the hole?
Were you using a tap wrench?
Were you using cutting compound?
Did you feed in around 1/2 to 3/4's of a turn and then turn it back to break the chip?
Were both taped holes the same depth?
Did you start with a taper,inter and plug?

actually snaped a 2.5mm drill bit in that hole too, yes did use rtd, use the stuff liberally , hole was through, only used a starter tap, pretty sure it was square, turned it ccw to break the chips but i noticed in the other holes and the first it cut like butter and swarf curled out the other end.
im convinced there must have been slag in there, it was virtually all the way through when it seized up, couldn't move it in either direction, had to make a pin punch to get it out, forget about it been a 3mm hole anymore.

should i have put some heat onto the area then try turning it out when it seized up? would that have done it or would i have just stuffed up the tap regardless?

Heat may of worked,for that size hole and tap the heat would of transferred pretty quickly probably giving the same end result.
You said that you broke a drill in the same hole.
Did you then run another drill through the hole?
Did the drill break going through the material or as it broke through?

yeah , the drill bit was just poking its head out the other side when it snaped, come to think of it i recon i felt a crunch like glass breaking. i was able to knock out the broken drill bit with a punch and resharpen and finish drilling the hole.

That crunch would of been the HSS starting to break.
There may of been the chance that there was a little bit of HSS from the drill still in the hole even though it was re-drilled.
Did the Tap break near the end of the hole similar to where the drill broke?

Depending on what thickness you where tapping and what weight the 3mm thread has to hold, you can get away with it not being full depth thread.
If I am going into something thick I can usually get away with 2.6-2.7mm drill to make taping easier. If it's only thin you are better off with full depth though.

Dave

hi mate you semm pretty handy.. i was going to suggest drilling a little bigger as well. 3mm is pretty small. have you cut many threads with taps? were they good ones

its only to hold a decorative ring on a pot belly door which is 6mm thick and the ring is stainless, about 2mm, the pitch on the screw i think is .5 from memory so i could have gone slightly larger in hole, possibly to 2.7 as its not really holding anything just there for looks more then anything. ended up giving that one a couple of light taps with a hammer and tacking it on the back side.
these are my first 3mm holes ive tapped, had to make a tap holder for the little buggers too.