Anyone had any success with one of these? I've had one for 20+ years. My first attempts produced drills with a negative clearance behind the cutting edge. No matter what I did (or friends who tried) it would not grind the correct clearance. I contacted the suppliers who replaced it with another. Unfortunately just the same results.

I really should have asked for a refund at that time, instead it was placed on a shelf in the workshop and forgotten about. That is until a recent thread on this forum reminded about it. So had another go, same results.

So, what am I doing wrong, any ideas?

I've now looked at several forums on this subject, some say they work well, others have had the same experience as me. The fact they can work makes me think its me rather than the machine, surely not a manufacturing fault?

In the intervening years I used a Draper attachment on a bench grinder, cheap and nasty but worked well! The I bought a drill grinder similar to Warco's, a super piece of kit!