Which chuck to choose

[Arutha]

I'm planning to buy a new chuck, but am not sure what to choose.

I do need a chuck with an option to turn my own threads. Either a threaded insert or a backplate.
My lathe is an old Swedish Rex lathe with BSW (Whitworth) 1 1/4" x 7 thread on the spindle, and I doubt anyone supplies inserts or backplates for this thread.

I looked at the Axminster SK114, but it does not seem to have blank inserts for turning your own threads.

The Versachuck has replacable backplates.

The Sorby Patriot is also an option, as well as Vicmarc.

I would prefer to be able to purchase an accurate insert or backplate for my lathe, but I do not believe this is possible. The next best option is a blank insert or backplate, that a machine shop can thread for me.

I know little about metal turning, but I do know that, for precision work, it would be preferable to make the complete insert without remounting. I.e. both the male and the female thread should be made by the machine shop.

A blank insert supplied by the chuck manufacturer is probably usable, but I doubt you'd get the same kind of precision.

I think it should be easier to turn an accurate thread using a blank backplate, as it should be easier to register in the correct position (than a blank insert).

 

[CHJ]

If you do not invisage having the lathe spindle replaced or modified to a more readily available thread standard by a machine shop, I would suggest your best bet would be the Versa chuck and Blank ISO back plate that can be machined to suit the spindle nose.

A machinist will need to know the specifics of thread length and the register diameter and depth.
See this sketch for guide to dimensions needed

 

[Arutha]

Thanks.

The Versa chuck is interesting, as it is mounted with an iso backplate.

What do you think about the blank inserts that chuck manufacturers can provide? Is it difficult for a machinist to produce an accurate, threaded, insert using one of these?

From what I've heard, to get maximum precision, you should make the complete insert without remounting.

Not sure if it would cost me more to have an insert made from scratch, or to buy a blank insert and have a machinist finish it for me.

But I think an iso backplate might be a safer choice. But the only woodturning chuck I've found that uses backplates is the Versa chuck. So not much to choose from. But many people seem to like the Versa chuck.

 

[CHJ]

If an insert has an outer Male thread to locate in the chuck as opposed to a plain sleeve then a machinist has to first machine a female thread in a sacrificial blank held in a chuck or collet to hold the insert in true alignment so that it too can be bored and threaded to match your spindle.

As far as machining costs are concerned.

A Male Gauge blank needs turning to match your spindle, preferably using an existing faceplate or similar that fits the lathe to check for fit. (alternate is to take the spindle out of the lathe)

This is then used to check the Female bore thread in the Backplate or Insert.

So one extra machined 'throw away' piece for a Back Plate, two for an externally threaded Blank Insert.

It's not just a case of boring a hole and cutting a thread, holding methods and sizing gauges have to be considered.

 

[Arutha]

Thanks. Interesting to hear how metal work is done.