Pen spring.

Adjustment on a lathe? That’s a stout spring!

I came out of the gate pretty damn obscure with this one. It's a piston cylinder hone for engine blocks. The next one will be more recognizable (or will it?)

nostr:npub1w975kchdvcw7c50m8xtzw29yynwsp78dk6x693fg2xme5zkj23js6xgfqv

nostr:npub14eng8plhflea40cu3lafnw6nwkxsp5te2v7hzy74lz6a9mjhpaks0wm4rw