That old machinist who showed me his trick for tapping holes without breaking a tap

Back at my first shop in Pittsburgh, this guy named Dan told me to use a little bit of sulfur-based cutting oil and back the tap out every quarter turn, and I swear I haven't snapped a single tap since then - has anyone else had a random old-timer drop a tip that just stuck with you?

3 comments

3 Comments

the_joseph24d ago

Use a left hand drill bit first if the tap breaks. Thats the trick nobody talks about. Dan probably knew it too but didnt tell you cause he wanted you to learn the hard way. A left hand bit spins backwards so it catches the broken tap and backs it out while drilling into it. Saves your part every time. Combine that with the sulfur oil and backing out every quarter turn and you basically never lose a hole to a snapped tap. Old guys hoard the best secrets like its treasure.

fiona98523d agoMost Upvoted

Funny you mention that, my dad had a similar trick for stripped screws that he swore by. He'd tap a flathead screwdriver into the head with a hammer just enough to get a grip, then twist it out slow and steady. Said it was the same principle as those left hand bits, just a different tool for the job. Ever tried that method on a stubborn screw that wouldn't budge?

seanjackson23d ago

Ive tried that and ended up tapping my thumb instead.