What size lathe chuck key?

[challenger]

My Sheldon lathe has 2 chucks with the same size jaw tightening. The key measures .392. What size chuck key is this?
Thanks

[nickel-city-fab]

I would call that 10mm

[challenger]

I would call that 10mm

Yup. I posted and went right to my "convert" app to find it is 10mm. For some reason I never thought this lathe would have a metric chuck. Stupid me.

[reggie_obe]

Yup. I posted and went right to my "convert" app to find it is 10mm. For some reason I never thought this lathe would have a metric chuck. Stupid me.

A Sheldon lathe, what brand chuck? Not a metric key unless it's an offshore chuck.

[Doozer]

I would make it .392".
What is the question ?

-D

[challenger]

A Sheldon lathe, what brand chuck? Not a metric key unless it's an offshore chuck.

Both chucks came with the lathe when I purchased it used abou 15 years ago and neither have a maker stamp etc. AFAIK they were issued with the lathe so?
I have a key for the chucks but wanted a longer one because the handle jams against the jaws of the 4jaw when I reverse the jaws.

[wierdscience]

Could also be 25/64 " =.3906

[reggie_obe]

AFAIK they were issued with the lathe so?.

It's very unlikely that Sheldon would have sourced CCC chucks, so it's not 10mm.
The beauty of making your own lath chuck key, make it suit you needs.

[754]

Yeah but I doubt it..

[nickel-city-fab]

I would bet that they are offshore, replacement chucks.

[old mart]

Polish made chucks would likely have a metric key. As the measured size is 0.0017007" different from 10mm, it certainly isn't a 3/8" one. Perhaps the makers name is on the chucks, it is common practice.

[MattiJ]

It's very unlikely that Sheldon would have sourced CCC chucks, so it's not 10mm.
The beauty of making your own lath chuck key, make it suit you needs.

From what I have read back in the day quite many chucks were imported from Poland (Bison, Toolmex) and TOS chucks from Czechoslovakia(spelling?)

[754]

Pull a mounting bolt, my money says its Metric..

[old mart]

Amongst the collection of chucks at the museum are two 5" Pratt Burnerds and a good 125mm Chinese one, the PB's use 3/8" keys and the other one uses 10mm. I generally use the smaller keys for all three as it is easier.

[reggie_obe]

Quoting a Sheldon Engineer,
"Sheldon did not make any chucks. However if a customer wanted to have a chuck fitted to the lathe when he ordered it the customer was given a choice of selecting the maker or if it was up to Sheldon depending on what type, style, etc the customer wanted Sheldon would most likely purchase it from Buck, Cushman, Skinner, or Hauton to list a few I can think of at the moment. Backing plates were custom made in the assembly dpt. for flat-back chucks for threaded spindles per orders. Regards, John K"