They have very tiny threads

They’re were in a bag at “creative reuse”, which is like a thrift store of art supplies. Each is rounded at the end, like a glow plug. They have tiny helical grooves, about the size of those on a vinyl LP record. They have bluing on them, but also rust, so I’m pretty sure they’re all steel and not carbide. When I shook the bad this little bamboo bead fell out as well, and it slid neatly over the cylinder (which remained unharmed). The square ends make me think of taps or easy-outs. They are right-hand threads. And there was a bag full of them, about 8lbs.