Direct fit collet chucks normally allow you to pass stock right through the head stock which can be very handy. Morse taper shanked chucks work fine but should be secured with a draw bolt.

RDG not RGD.

Ideally you would have an ER16 chuck that screws on to the 3/4" thread on the headstock – something like this one from Taig:

**LINK**

1045ER ER 16 Adapter for 3/4-16 spindle

Others are available.

That way you spend a lot less ($30 plays $200 at US prices), can carry on using all your MT1 tooling, and pass longer stock through the chuck into the spindle.

MT to ER chucks are really for milling.

I know this is a wild goose chase, but my very early Cowells has M14*1.5 spindle nose. Anyone got any idea where I'd buy an adaptor like the one John Haine linked? I could make a new spindle, but then existing chucks etc wouldn't fit. I don't anticipate working up the energy to make an adaptor any time soon.

Please look up Axminster Junior chuck.

ER20, will fit Taig spindle at 3/4-16 so should also fit Sherline.

In the past, Axminster would make you an adaptor for this chuck, so if this service is still offered, the M14 x 1.5 might be possible.

The back of the chuck is recessed and the periphery of the recess should be concentric to the chuck. There needs to be a "spigot" on the backplate, that is a "raised" portion from the centre to a radius that fits snugly into the recess, to centre the chuck on the backplate. I think there is probably already a spigot machined but the diameter will be too large.

The idea is to fit the backplate to your lathe, turn the spigot to the exact diameter to fit the chuck and also face the outer "flange" (the bit where the mounting holes are) so it is perpendicular to the spindle axis. The spigot "height" should be slightly less than the depth of the recess. The mounting holes will have a clearance so the chuck position is fixed by the spigot and the outer flange, you can't rely on them to centre the chuck. It's a slightly tricky job but good practice!

In case there is any confusion.

Adding a backplate for a chuck will involve two registers.

One will be register that locates the backplate to the Mandrel of the lathe. The back of the register recess needs to be perpendicular ("square" ) to the ID off the backplate register to ensure that the bacfkplate runs as true as possible, and as repeatably, as possible, to the axis of the Mandrel. .

The second register is that the O D needs to be turned to provide an accurate register for the chuck destined to be fitted to that backplate.

It is essential that the chuck is located accurately along the lathe axis, not an angle to it.

So the backplate needs to be faced so that the chuck is located both radially and axially.

A prefinished backplate should have the register meeting these conditions, so that it only needs the OD to be machined to size, and faced.

Howard