Hi DGC ,

There are really only two credible solutions to your problem :

Use the existing spindle and make all chuck backplates and other fittings new to suit .

Make a new spindle with Myford spindle nose and use standard Myford backplates and fittings ..

There is no credible solution using an adapter .

The easiest and best of theses solutions is to keep existing spindle . Making new chuck backplates is not difficult .

To bore the accurate spindle register you will need to first make a gauge which is a short piece of bar turned to EXACTLY the same diameter as existing spindle register . You may need to have more than one go but you'll soon have success . For the thread I recommend that you basically screwcut the thread but use a bought tap to actually finish to size – it'll be a standard thread and people like Tracy Tools will probably find you a tap .

So with backplate casting mounted in chuck or on face plate boss outwards :

Face off end of boss , drill and bore the through hole undersize and then bore core size for thread .

Screwcut thread and finish with tap (tap may not have enough clearance to go right through to back but cut as much as possible in place and if needs be finish later ) .

Very carefully bore the spindle register using your pre-made gauge . Aim to have gauge a very close fit in bore .

Optionally finish machine the other surfaces at boss end of backplate .

Mount partially made backplate on actual lathe spindle and turn the chuck register and and other surfaces .

Take great care with all the final sizing of spindle and chuck registers – take very fine cuts and don't go full length in one go – try a very little bit at the end of register for fit each time and then turn the full length as appropriate .

The above is a good way of making backplates if you have limited experience but there are better more high precision methods which we can talk about another time if you want to .

NB : Its the spindle register that does the alignment of chuck and backplate to spindle . The thread would ideally be accurate but to a definately lesser degree than the register .

Ask me any questions you would like .

Regards ,

Michael Wiliiams .