End Mill Holders
I bought a collection of end mills with 3/8" shanks. I wanted to have a consistent shank size for all my end mills, and all the sizes I wanted were available with a 3/8" shank. I purchased a Sherline end mill holder which threads on the spindle, but it was really expensive (~$30) for a threaded and bored piece of steel. I wanted to have a bunch of end mill holders for the commonly used sizes, but I couldn't afford them at the Sherline prices. I found blanks for the Taig tools that were already threaded for the spindle. If I remember correctly, I got these from Carter Tools and they were under $3 apiece. The Taig spindle projects farther from the headstock and has more threads than the Sherline. In the pictures, you can see that the threading does not come out to the end on these blanks.
I put the blank in the lathe chuck, threads toward the tailstock, and faced the end until the threads started immediately at the shoulder. I chamfered both inside and outside edges. I removed the chuck and threaded the blank directly to the spindle. The lathe and mill use the same spindle, so this is very convenient. The newly faced end registers on the spindle, so all the remaining operations were performed on this setup so everything runs true with the spindle. I turned the outer diameter just enough the clean it up and make it concentric with the spindle. I faced a bit off the end to shorten it up and chamfered the outer edge. I center drilled the face and drilled through with a bit slightly smaller than 3/8". I then used a boring bar to enlarge the hole until I had a very snug, sliding fit with a 3/8" end mill. I measured the original holder for the set screw and tommy bar hole distance from the end and drilled these holes in the mill. After drilling and tapping, I used a small file to carefully clean up the burrs on the inside of the bore. This is an easy project to turn a $3 blank into a $30 tool. You just need to make sure the bore runs true to the spindle and isn't oversized. Click the pictures for larger images.
I put the blank in the lathe chuck, threads toward the tailstock, and faced the end until the threads started immediately at the shoulder. I chamfered both inside and outside edges. I removed the chuck and threaded the blank directly to the spindle. The lathe and mill use the same spindle, so this is very convenient. The newly faced end registers on the spindle, so all the remaining operations were performed on this setup so everything runs true with the spindle. I turned the outer diameter just enough the clean it up and make it concentric with the spindle. I faced a bit off the end to shorten it up and chamfered the outer edge. I center drilled the face and drilled through with a bit slightly smaller than 3/8". I then used a boring bar to enlarge the hole until I had a very snug, sliding fit with a 3/8" end mill. I measured the original holder for the set screw and tommy bar hole distance from the end and drilled these holes in the mill. After drilling and tapping, I used a small file to carefully clean up the burrs on the inside of the bore. This is an easy project to turn a $3 blank into a $30 tool. You just need to make sure the bore runs true to the spindle and isn't oversized. Click the pictures for larger images.