I bought a “Unibit” type of tapered drill bit from China, a large one. It cuts up to 36mm but the shank is 1/2 inch or 13 mm. I want to put it in a 1/4 inch or 6.5mm chuck. The only drill I have with a half inch chuck is a big hammer drill. So I decided to see if I could spin the bit in the hammer drill and file down the shank. I tried a file, but it just polished the hardened shank. Same thing happened with a hacksaw blade. So I got a fine grit diamond coated file, and that started to cut into the shank, but I didn’t see any metal shavings coming off, so I gave up.
I think the shank is too hard to do it with the tools I have. The shank needs to be in a lathe, and ground down with a grinding wheel. I need to find someone who has a lathe and can do it for me. It’s tough getting things to work like you want.
