Broken #21 Drill Bit in mill part.

I don't think the flute length is that great on the Em I have in mind, but I'll look in the morning and let you know. I probably have something.
 
I have some solid carbide small end mills with 1/8" shanks,TIN coated. They are Chinese,and came in little plastic boxes of assorted ODD sizes,the largest about 1/8" down to 1/16". I used to get them from a guy with a large bunch of cheap Asian tools at a gun show. He may have died,haven't seen him in a while.

With these cheap little 4 flute end mills running at full speed in my Bridgeport,I have neatly reduced several broken taps that the gunsmith shop broke off in flintlock frizzen springs to dust. Didn't even touch the threads in the holes. I wish I knew where to get these little sets of 10 end mills that he sold for $10.00 a set. They have been great for frilling out HSS taps. Their cutting edges are only about 3/8" long,which likely helps them to not break.

This was one of my jobs when I was master toolmaker in Williamsburg-getting others out of jams.
 
One shop I worked at had a number of parts of some pretty tough to tap materials, so we were always breaking taps in them. Blind holes where the print called for us to tap the holes about 2 turns past the bottom of the hole, it seemed like. Everybody hated doing that part of the job. We didn't have a tap burner for a while, and one old timer had a method that should never have worked, but did. Mostly we had trouble with 1/4-20 holes, drilled with a #7 (0.2010). We took the butt end of a 3/16" carbide end mill and ground a 4 sided pyramid shaped point on it, and it was slightly larger than between the flutes of our taps. Running the mills wide open, around 2700 RPM and constant air blast, it just just the taps out like butter. I theorized that the friction softened up the tap, and the super negative edge held up to the pressure well enough to dust the tap. It would produce very tiny, very hot chips, but go right through the tap. Had to try and grind the broken end somewhat flat and square, if we could get to it, but it worked great. I still use that method once in a while.

Then we bought a tap burner. Messy, but easier. Unless you didn't stop when you got to the bottom of the tap or drill you had broken. Then you had a hole in the part.
 
george wilson said:
I have some solid carbide small end mills with 1/8" shanks,TIN coated. They are Chinese,and came in little plastic boxes of assorted ODD sizes,the largest about 1/8" down to 1/16". I used to get them from a guy with a large bunch of cheap Asian tools at a gun show. He may have died,haven't seen him in a while.

With these cheap little 4 flute end mills running at full speed in my Bridgeport,I have neatly reduced several broken taps that the gunsmith shop broke off in flintlock frizzen springs to dust. Didn't even touch the threads in the holes. I wish I knew where to get these little sets of 10 end mills that he sold for $10.00 a set. They have been great for frilling out HSS taps. Their cutting edges are only about 3/8" long,which likely helps them to not break.

This was one of my jobs when I was master toolmaker in Williamsburg-getting others out of jams.
Click to expand...

HF used to sell those in used assortments; alas no longer.
They've dropped a lot of useful stuff over the years. :(

M
 
When I was starting out,with a limited budget,I sometimes made effective small milling cutters by grinding a broken off tap's threads completely off,then grinding a short portion of the remaining body triangular. The end of the cutter was ground at an angle to make it cut there(scrape,actually) also. These were small end mills 1/16" or less in diameter. They scraped very efficiently on brass mostly(I was making a lot of small things from brass back then). The cutting flutes were about 1/8" long,and I ran them fast.

I got the idea from very old taps,which in the 18th. and 19th. C. were often just square or triangular,but cut threads well,anyway. I still make an odd tap for repairing a mechanical antique that same way.
 
george wilson said:
When I was starting out,with a limited budget,I sometimes made effective small milling cutters by grinding a broken off tap's threads completely off,then grinding a short portion of the remaining body triangular. The end of the cutter was ground at an angle to make it cut there(scrape,actually) also. These were small end mills 1/16" or less in diameter. They scraped very efficiently on brass mostly(I was making a lot of small things from brass back then). The cutting flutes were about 1/8" long,and I ran them fast.

I got the idea from very old taps,which in the 18th. and 19th. C. were often just square or triangular,but cut threads well,anyway. I still make an odd tap for repairing a mechanical antique that same way.
Click to expand...



George, you and I may have attended the same schools back when.....you know, back in the late 1700s.:whistle::))
 
I DID work in Colonial Williamsburg for 39 years,and developed an interest in early ways of doing things that transferred to machining! I studied lots of old books,and knew old machinists who had had to get work done with MINIMAL resources years ago,when that was the order of the day in many small shops.
 
Want to thank everyone for the help, I got a 3/32 carbide ball nose end mill and cut the drill out.

Here is a picture of it painted and back together. It also took out the rest of the broken screw and all I had to do was chase the threads.

Paul

Support.JPG
 
Always did like a happy ending Paul.

"Billy G" :))
 
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