We’ve had this metal sphere knocking around in the basement and the shed for decades and I am curious what it was originally intended for or used for.
It’s 2.375 inches in diameter give or take maybe a couple mils, as best I could measure with my cheap home calipers. It’s dense, like steel, and holds a magnet. It’s mostly shiny, and the reflections are unchanging as I rotate it – there’s no wavering of the image, as in the reflections from a shiny spherical Christmas tree ornament – so it is as spherical as I can judge by eye. It has patches of very faint corrosion, like fine rust but dark brownish gray rather than vivid flaking brick-orange as in pure iron rust. It has no features anyplace on it; no seam or mold flashing, no holes or flats. Considering that it was often kept in boxes of junk or loose on workbenches and shelves, it surprisingly has no visible scratches or dents that I can find.
I suspect that it is a ball from a huge industrial ball bearing. Such a ball would be harder than typical steel, perhaps containing lots of chromium or other alloying agents. Or it might be a 400 series stainless steel, which would be hard, and rust slightly, and hold a magnet. One of the people in the household used to work for a photographer and helped with an advertising project for a maker of such bearings, some of them big enough to walk through, and would clean off the parts with solvent and rags. However this person has no memory of this ball, so that might be a red herring.
I am sure this is not from a ball mill. I have worked around ball mills, and those balls are coarse and typically depart visibly from spheres.
Any ideas? Any suggestions on how I could confirm it is a bearing ball, or disprove that it is?