Originally Posted by Ironwood
Thats funny, I have done hundreds and never a broken tap. I can hold a drill steadier than I can a tap handle. Don't over tighten the chuck and you will be fine. If it starts to slip in the chuck, just reverse a a few turns and go in again. Fast and accurate.
I agree with this method I tap holes ALL THE TIME using this same method. Haven't broken a tap in over a decade.
Drill the correct hole, use plenty of cutting fluid and don't reef down on the chuck. It's almost foolproof. I use the same method tapping smaller holes on the lathe. The grip on the tap depends on a bunch of different factors but not tightening the chuck all the way acts as a clutch.
I probably tap 95% of my holes using a chuck either in the lathe, drillpress or cordless drill.