Thread: Info from USA on spindle nose register

Jordan,
As I understand it, register fit refers to the backplate/chuck interface and this needs to be close to ensure that the chuck mounts solidly and securely on the shoulder.
I can understand that a threaded chuck needs a good square helix to pull up on, but most chucks now come suitable for backplate mounting unless manufacturer specific?

Cheers Phil

G'day Phil,

Some Hercus supplied chuck bodies were directly threaded, others had backplates. In either case, there is clearance on the cylindrical "register", which is just a plain, unthreaded portion beyond the thread. Hercus/South Bend don't use a stepped shoulder like on Myford for example.
The findings in the US were that repeatable accuracy was improved by NOT having a close fitting cylindrical register.

Jordan

The register fit you reffer to is the fit of the spigot machined onto the front of a backing plate that fits into the recess in the back of the chuck.

The register on the spindle is the face that the chuck backing plate seats against when srewed onto the spindle.

Originally Posted by nadroj

The southbendlathe Yahoo group had a recent posting regarding the importance of a close register fit. In short - it's not important. A good thread helix made square to the register helix was found to be better.
This is reportedly the finding of experiments 50 years ago, by chuck and lathe makers.
Hercus were evidently aware of this, as they didn't use a close fit for the chucks.

Jordan

- most American designed lathes with threaded spindle nose use indeed only the threads and the face for registration. Hercus lathes are an American design.

- many European designed lathes with threaded spindle nose use additionally a separate registration flange (as in the DIN800 spiondle nose) to achieve a higher degree of accuracy. The Swiss made Schaublin lathes are such an example.-

I can recommend this thread if really interested in this subject, but it is long:
Machinist meaning of "Register" ? - Page 3

Chris

I read some of that thread - more heat than light!
The US info mentioned is from manufacturers.

Jordan