View Full Version : New (to me) tap removal method..

02-24-2008, 11:30 PM
Wouldn't you know it.. I was finishing off the panel brackets for the new control panel I'm building for my bandsaw.
I hand drilled and tapped the cast legs of the base to hold the brackets.
Of course...the very last one...yup, I left the hardest one til last...the #&%*$^&%ing tap broke off. Sort of an ugly place, up under the motor. I'm sure I prolly drilled the hole crooked, that's why the tap broke I'm sure.
Tried for two hours to get it out. Tried vicegrips, needlenose pliers, sidecutters, picks and center punches. Nothing.
Was going to heat up the tap with the torch then try to drill it out.
But what the heck...I have an almost perfect conical nib sticking dead center out of the broken tap. That little nib would fit right perfect up inside of the nozzle on my plasma cutter.
Set it up...a half second later the tap was gone...the hole was almost untouched. Cool!
Run the tap drill through..not bad.. I can live with this. Try...try....try to tap it. Whoa...that hole is as hard as diamonds now.
OK...drill it out to the next size. Holy Chit is it hard. Finally get the hole drilled. Try and try to tap it. Dulled a tap. Grab another...eventually got the hole.
New method...it worked ok. The bracket still looks good even if the bolt there is bigger.
I'm betting it would work better on mild steel. The heat melted out the carbon in the cast I guess...maybe some of the tap metal got into it...it was some hard.
So maybe...someday down the road, this little stunt could save YOUR butt too :D

02-24-2008, 11:43 PM
Thanks Russ, I actually would not have thought to use the plasma. Even though Ill cut everything else with it cause its down right fun..

Curious, did you turn down the power on it.. I always forget to turn it down, I leave it cranked to max when I really do get a nicer cut on sheet metal when I turn her down abit. I gotta start thinking more and stop acting quickly as much. JRouche

02-24-2008, 11:45 PM
I've never tried a plasma cutter for that either, but I've cut a number of taps and bolts out of cast iron with an OA torch. If the hole is 1/4 inch or larger, it is easy, and seldom if ever harms the existing threads.

02-24-2008, 11:46 PM
JR..it was cranked wide open. The cast was about 1/2" thick and the tap broke off with about 1/4" of the tip sticking out. Too tight to get anything to grab the tip.

dirty old man
02-25-2008, 12:00 AM
Never tried it on a hss tap, but many is the time I have used an OA torch to blow a frozen, rusty, wrung off bolt out of a clear hole in a cast iron part, usually an exhaust manifold from a motor vehicle.
Works better if you can first drill a hole thru the bolt, and no, you can't drill that tap. But that bolt ain't got 3 or 4 grooves between flutes, either! If cutting steel out of cast iron, OA works better than plasma as OA won't cut cast iron, only melt it if you get it that hot. Consequently, if you can get the steel hot enough to cut with the oxygen jet without getting the cast iron hot enough to melt, you can blow that bolt, and I'm guessing a tap, right out the other side of that clear hole.
It's a technique worth learning and getting a bit of practice when you see cast iron parts with tapped holes, or bolts scewed into tapped holes, on it's way to the scrap yard. Just waylay it awhile, and then it'll bring a better price as clean cast iron.

02-25-2008, 12:10 AM
and no, you can't drill that tap.
Yes, I can. Hit it with the torch to bright cherry...keep the heat on and let it cool slow. Then drill it out with a masonary carbide drill bit as per weirdsciences instuctions. I've done several of them like that now. This was too hard to get at to do a good job.

02-25-2008, 12:28 AM
Yep O/A in cast iron works great. Thats the quick and dirty for getting broken exhaust studs out. Too bad i didn't know that earlier ... :)

02-25-2008, 05:29 AM
Heat end up red with cuttin torch then hit the oxygen tap gets blown out.

Your Old Dog
02-25-2008, 05:38 AM
I'm reserving comment until Sir John weighs in :D

02-25-2008, 06:40 AM
I'm going to try the torch thing. I've done it with bolts and studs...but...this was just a small hole (#7)(for 1/4X20) that's a half inch deep. It was maybe threaded halfway.
I'm betting the torch makes hard spots also.