Mate Alan wanted fit some new flush handles to a folding bathroom door. These required a large hole cutting in the door and a hole saw seemed ideal for the job. He had inherited a hole saw mandrel but it was manually rotated using a tommy bar. “Can you make it work with a drill?” he asked.
The mandrel was hacksawed into two parts near to the handle end.
The shank then needed reducing to 12mm so that it would fit into a drill chuck. Because I only have a small lathe chuck I had to tighten on the screwthreads which was not ideal and did not give a lot of support. The supplement this, I centre drilled the end and supported the mandrel from the end with a half centre. I then faced and turned the rod. There was some damage to the threads so I used a trianglar file to repair them. A better approach might have been to use some softjaws or it might have been possible to turn it between centres as it had a hole in the threaded end.
It’s not my neatest of jobs but it should be accurate enough to drill the required hole.