Lathe chucks

[Screwdriver]

The chuck is bolted to the backplate. Usual form when you mount a chuck is to turn a step in the backplate (called a register) to a close fit in the back of the chuck so the chuck turns perfectly concentric with the backplate. The problem is that (most) 3-jaw scroll chuck are not perfectly repeatable (since you need some clearance for the scroll to turn) so depending on the quality and useage the work will run out to differing amounts. What you can do is turn the register a few thou small so that the chuck can move about a little. If you want your work to run perfectly true in the jaws you slacken the bolts on the backplate slightly and use a plastic/hide/lead hammer to bump the chuck until the work runs as true as you require. I'd like to claim credit for the idea but I learned it from a post by John Stevenson.

I have found though that if you mark the work & chuck with a magic marker and put it back in exactly on the mark - more often than not it will repeat quite closely.

That would not fix a problem with the scroll issue as described above though. Sounds Like a new chuck is the only option.

S.

 

[Pete.]

I never meant to suggest it would, just to point out that even a budget 3-jaw can be adjusted for no runout so long as the work is held co-axial to the spindle.

 

[hareng]

If you are short of the D1-4 just buy a Bison integral D1-4 and be done with it. D1-4 plates ok from RDG about £50 just need to turn down, do the register and so on.
Still using two small 5 1/4" Bison one had on toy Myford 20 yrs ago, jaws worn now lives on rotary table. You can get the soft jaws from a place in Hockley Brum about £40 and sell on ebay.
Bison on to L00 fitting back plate.

Same 5 1/4" chuck on to a D1-4 backing plate rear fixing can just about do it.

Like anything Chinese the quality of workmanship is wildly unreliable though do have integral 8" D1-4 that is accurate.
If you do go integral ie inbuilt into chuck with D1-4 fitting, you will have less stress on bearings with the chuck closer to headstock and gain some valuable length between centres.

 

[Spark plug]

I've seen some Pratt chucks on tinted net that seem reasonable but I'm going to call 600 first just in case they are cheeper, I may pass out if they actually are.

I've noticed some of the Chinese ones don't advertise there speed rating either.

 

[Spark plug]

Ok I called 600 today and they weren't to bad price wise but I have found the same chuck slightly cheeper elseware so Ile probably order that next week.

 

[ukracer]

Ok I called 600 today and they weren't to bad price wise but I have found the same chuck slightly cheeper elseware so Ile probably order that next week.

What price. size and supplier was it mate??

 

[hareng]

Pratt do an economy range not that much dearer than Bison/Polish.

Wouldn't mind a nice small 6 jaw D1-4

 

[Spark plug]

What price. size and supplier was it mate??

Ile PM you the details.

 

[roofman]

This afternoon i stripped and cleaned my 9" 4 jaw for my new Harrison...2 years ago i lent my 4 jaw from my other lathe to a friend...never ever got it back so lesson learnt