Mystery Lathe Chuck

[paulygman]

I picked up two small lathe chucks last weekend at an auction sale, one is a 3" 3 jaw chuck stamped A F CUSHMAN MAKER ...... HARTFORD CONN ...... Pat Nov 14 1871. The second is a 3-1/2" chuck has 4 jaws, the chuck jaws are not completely independent as they work in pairs, the jaws are about 1/4" in height, the back side mounting is a 1/2" diameter socket with a set screw. Pictures are below, can anyone tell me what the second chuck would have been used for? Thanks paulygman.

 

[4ssss]

Maybe on a Comparator?

 

[woodchucker]

I picked up two small lathe chucks last weekend at an auction sale, one is a 3" 3 jaw chuck stamped A F CUSHMAN MAKER ...... HARTFORD CONN ...... Pat Nov 14 1871. The second is a 3-1/2" chuck has 4 jaws, the chuck jaws are not completely independent as they work in pairs, the jaws are about 1/4" in height, the back side mounting is a 1/2" diameter socket with a set screw. Pictures are below, can anyone tell me what the second chuck would have been used for? Thanks paulygman.

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Interesting, a lot of neat little features on that 4 jaw.
First, the screws are pulling rather than pushing toward the center.
The jaws on the larger 2, have a bevel cut that is pulling the piece toward the body of the chuck.
It is self centering for each pair.
Pretty interesting based on the patent date.

 

[Silverbullet]

I would bet it's an engraving block , for jewelry or gunsmith . I think the base would be just as interesting if you had it.