Vintage Starrett dividers

[paulm12]

from a recent box of tools I picked up: an older Starrett spring divider with an unusual (to me) locking nut

- the logo is "The L.S.S. Co" "Athol, Mass, USA"
- it also has a logo/stamp on each leg " AWA Chicago" I think
- the nut is split in a manner that the inner threads only engage when compressed, which happens when the nut is pressed against the divider leg. When loose the nut flops open, and easily just falls off the end of the threaded rod. The nut has a patent date of Jul 4 1905 (is more legible than the picture shows).

Has anyone else seen one like this?
.

 

[notlob]

Very common on Starrett calipers and dividers - I have a bunch of them. There should be a small ball affixed to the end of the threaded rod to prevent the nut/thumbwheel from coming off. I believe you are also missing the cup-shaped piece that should be between the split nut and the divider leg.

Here is Laroy S. Starrett's patent for the split nut:

https://www.google.com/patents/US793850

Here's a pic showing the ball:

 

[paulm12]

thanks Not. I wasn't sure if the ball was missing or never there. thanks for the link.