Yes, pics would be right handy. If you have an M Type Drummond you have a good old machine. Quite a few owners of them on here. As well as lathes.co.uk, a good resource is to join the Yahoo Groups drummondlathes group and have a look through the info in the FILES section etc.
Usually with chucks, you will need to buy the size you want, possibly a 5" (125mm) depending on lathe, and then either machine the old chuck backplate to suit it and bolt the chuck on to the backplate, or you can buy a backplate blank from lathes.co.uk or elsewhere and machine it up yourself, which may be a bit tricky for a beginner as it needs to be accurately screw cut and machined to fit the spindle.
Post some pics of your existing chuck/s and the panel can probably advise further.
Edited By Hopper on 20/05/2017 11:30:03