Re: Spindle register issue


I will do the experiment tomorrow night. I have 3 SB in the basement ( one is not powered, being in storage)

I will turn a piece and move it from lathe to lathe and take measurements.

I am quite sure the lathe with altered register will always be off.

We will see how repetitive readings will be.

I am a strong believer that the altered register has an effect on chuck Alignment. We will also see if the high point repeats as well.

I will publish results tomorrow.
In the meanwhile, the question about register rebuild is in the air.

Worst case scenario, the original 9A spindle will be back in commission until I find a viable solution

Guy Cadrin

---------- Original Messagea ----------
From: "Davis Johnson" <davis@...>
Subject: Re: [SouthBendLathe] Spindle register issue
Date: Thu, 21 Jun 2018 20:28:43 -0400

HTRL agrees with you (heresy around here, tho).

I'd be interested in an experiment.

Chuck up a short piece of scrap, turn the outside for a bit.

The part you just turned will be exactly concentric. Check it with an

Unmount/remount the chuck several times without removing the piece of
scrap. Each time check it with an indicator.

I really would be interested in the results, and would do the experiment
myself except that I don't have a chuck with a loose register.

On 06/21/2018 08:15 PM, m. allan noah wrote:
I'll buck the conventional wisdom, and state that the register
diameter does not matter at all. The conical face of the thread, and
the flat shoulder behind the register are sufficiently to achieve
kinematic positioning of the chuck.

I daresay the problem is your testing method. Reground jaws is
basically meaningless, unless they were ground on the lathe in
question, properly preloaded, with the diameter set to exactly the
size of the stock you are now holding. Take of the chuck, and put it
back on, and see if it is consistent. That is a true test.


On Thu, Jun 21, 2018 at 8:00 PM, carbure2003 <guycad@...> wrote:
About. a year ago, I bought a 10K spindle on ebay.

As I have not used much the lathe where I fitted the spindle, ( only with collets) I never noticed that the register was under sized. (1.495 in dia), quite likely machined by a previous owner.

I trialed a chuck with freshly re ground jaws on it and it was defenitely off centered by many thou.

Register defenitely has importance when yo want to swap chucks from lathe to lathe and keep chuck accuracy.
Did somebody ever attempt to rebuild a spindle register ? (Register is 1.510 in dia on my other SB)

If yes, how did you proceed? (Welding is not an option)


Guy Cadrin
70s Millionaire Returns with Surprising Prediction

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