I recently bought a few machinist chests full of tools and other goodies. I’m not a machinist myself, but I’m familiar with a lot of the tools associated with the trade. This piece is a smooth solid steel cylinder with four equal spaced holes bored completely through it. It measures approximately 5.5" long and 2.25" diameter. Weighs almost 4-1/2 lbs. The end has stamped “Feb. 48 Eddie Champ.” The other end is identical minus the engraving.
I suspect it might be a cylindrical square, but I’ve not seen examples quite like this. It came with a plastic sleeve.
I think it’s a cylindrical square. It can be set on one end on a surface plate to find 90°. Because it can be rotated, it can be checked for error. I think they’re often made by apprentice machinists, hence the name and date stamped in it.
Example commercial version: https://www.mscdirect.com/product/details/06504302?item=06504302
Example use of one with a surface gauge as a squareness comparator: https://youtu.be/53q6kVX9gjM?t=1244
I’m pretty sure it is a cylindrical square and was someone’s shop project in tradeschool or as an apprentice, or just from a slow day.
It’s a 4-barrel 10mm socket shooter.
Could it be an insert for calibrating temperature probes?
That was actually my first guess, but they’re usually bored blind. Also those would be some GIRTHY probes, lol.
