I was drilling and tapping bunch of 1/4-20 holes in mild steel and I stopped the machine after I thought drilling sounded little different than usual just to find that drill got little dull and it drilled one hole 0.22". No problem I thought, I just tap it with a form tap. I have to say I use form taps very seldom. The hole is fine when you check it with a thread gauge but dia reminded 0.22". Are form taps not recommended for mild steel? I used rigid tapping at 1000 RPM. Any thoughts? Jerry
- posted
15 years ago