11-09-2017, 06:09 PM
Well, I’m back to where I was several days ago. Here’s what happened yesterday:
I wasn’t lucky enough to be able to remove the broken tap by shattering into small pieces. I’ve read that suggestion many times over the years but it’s never worked for me. Nor have those cute little tap extractors (come to think of it, E-Z outs and I have had running battles, too).
Thinking about my woes with broken taps over the years, I’d like to diverge for a moment with a really weird story.
About fifteen years ago I broke a tap – also a #4-40 – in a Mauser receiver. I was active on PM at the time and posed the removal question in the gunsmithing part of that forum. I received the standard answers and one that shocked me. The guy who suggested it made the provision that it was a last resort but that it had worked for him.
For some reason, I didn’t think of using a solid carbide end mill at the time and I’d (mentally) exhausted my other options so I decided to try the unorthodox suggestion. Incidentally the Mauser receiver was a 1893 model and they were fairly easy to come by at the time so I wouldn’t have lost much if I’d ruined it.
I clamped the receiver in a vise and fired up my O/A torch with the smallest tip. Yep, he’s REALLY going to do it ! Following instructions and with as much precision as I could muster, I quickly heated the piece of tap red and then cranked up the oxygen on the mixing chamber. Bingo, blew the little pieces of tap out the receiver and bob’s yer uncle.
A factual anecdote and incidentally, I’d never try that again – the stars and planets were in perfect alignment on that day and at that time !
Returning to the current difficulty, I placed the little vise back in the set-up in the vertical mill and installed a solid carbide 1/8 inch end mill in the spindle. The highest speed on my mill is 3200 RPM, which is considerably slower than a 1/8 inch diameter carbide end mill should be running but I set the speed to 3200 having no other choice.
(I should point out at this time that I’ve also tried this carbide end mill trick in the past with about 30% success. The secret is slow, consistent downfeed so that the tips of the cutter don’t suddenly run into something and chip off. That’s hard to do with a broken tap because the cut is nearly always an interrupted one.)
Feeding as slowly and carefully as I could, I was able to mill out the broken tap, the aluminum insert and even a tiny bit of the hardened vise, ha-ha-ha, sparks occasionally flying out of the hole.
I found a 3/16 carbide drill and opened the hole up:
Now to make a new insert but THIS time I tapped the #4-40 hole while the insert was still in the lathe:
Epoxied the insert, as before and allowed to cure after which I cleaned up the area with some emery paper. One more tiny drama concluded.
I wasn’t lucky enough to be able to remove the broken tap by shattering into small pieces. I’ve read that suggestion many times over the years but it’s never worked for me. Nor have those cute little tap extractors (come to think of it, E-Z outs and I have had running battles, too).
Thinking about my woes with broken taps over the years, I’d like to diverge for a moment with a really weird story.
About fifteen years ago I broke a tap – also a #4-40 – in a Mauser receiver. I was active on PM at the time and posed the removal question in the gunsmithing part of that forum. I received the standard answers and one that shocked me. The guy who suggested it made the provision that it was a last resort but that it had worked for him.
For some reason, I didn’t think of using a solid carbide end mill at the time and I’d (mentally) exhausted my other options so I decided to try the unorthodox suggestion. Incidentally the Mauser receiver was a 1893 model and they were fairly easy to come by at the time so I wouldn’t have lost much if I’d ruined it.
I clamped the receiver in a vise and fired up my O/A torch with the smallest tip. Yep, he’s REALLY going to do it ! Following instructions and with as much precision as I could muster, I quickly heated the piece of tap red and then cranked up the oxygen on the mixing chamber. Bingo, blew the little pieces of tap out the receiver and bob’s yer uncle.
A factual anecdote and incidentally, I’d never try that again – the stars and planets were in perfect alignment on that day and at that time !
Returning to the current difficulty, I placed the little vise back in the set-up in the vertical mill and installed a solid carbide 1/8 inch end mill in the spindle. The highest speed on my mill is 3200 RPM, which is considerably slower than a 1/8 inch diameter carbide end mill should be running but I set the speed to 3200 having no other choice.
(I should point out at this time that I’ve also tried this carbide end mill trick in the past with about 30% success. The secret is slow, consistent downfeed so that the tips of the cutter don’t suddenly run into something and chip off. That’s hard to do with a broken tap because the cut is nearly always an interrupted one.)
Feeding as slowly and carefully as I could, I was able to mill out the broken tap, the aluminum insert and even a tiny bit of the hardened vise, ha-ha-ha, sparks occasionally flying out of the hole.
I found a 3/16 carbide drill and opened the hole up:
Now to make a new insert but THIS time I tapped the #4-40 hole while the insert was still in the lathe:
Epoxied the insert, as before and allowed to cure after which I cleaned up the area with some emery paper. One more tiny drama concluded.