Need help! The small screw that secures the grinder bit to the shaft was stuck and my efforts to loosen it resulted in stripping it. I've tried spraying it with lubricant -- still no luck. What can I do?
There is a tool that many mechanics and tool shops have. It is normally square or triangular. It is used by drilling into the broken off bolt, or in this case, the grub screw. The tool is hammered into the hole and then with a wrench/spanner loosened.
However, you should make sure that the socket for the allan key is clear of glass residues. I do this by using a needle or other thin sharp object to clear out all the glass powder. I am sure there are other things to clean out the hole too. When the socket is cleaned, I push the key into the socket very firmly and hold it there while turning. This has worked for me in the past.
Once the grub screw is out, you need to get a replacement, so the same problem does not re-occur. I keep the screws from old heads in my box of grinder parts for this eventuality.
So the maintenance is not only on the shaft but also on the fixings. Putting a dab of Vaseline or thick grease into the socket will help keep it clear of the glass residue.