In article ,
Dave Plowman wrote:
In article ,
JonBoy wrote:
...hit with a mallet or rubber hammer *in the correct direction* as
the chuck is (probably) on a LH thread.

No - a standard chuck has a right hand thread since basic drills go
clockwise. Reversing drills have a locking screw which is left hand thread.

Thanks for all the advice. Managed to do it. Retaining screw was LH
threaded and chuck was a normal RH thread.
Neil