Scott has it right...mostly. One yard I know about asks their customers to separate their swarf by metal type and supplies barrels for this. But this is hit and miss, so when they receive the swarf, they dump it out and go over it with an xray gun to make sure each barrel is a decent sort. This procedure is used for swarf that they pay for, like aluminum, stainless steel, brass, Inconel, etc.
Plain old steel swarf is received in dump bins. I don't think they pay for this but don't sort it either.
Jon.
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