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darryl
02-04-2010, 01:07 AM
Went to buy a piece of 1 1/4 round bar the other day. I asked for hot rolled or some kind of stress relieved material. The guy queried me, returning with 'cold rolled?'. No, I said, hot rolled or maybe leaded steel. Again, he came back with 'cold rolled-' again I said no, hot rolled or something that machines nicely.

As I only needed a short piece, 3 inches long to give something to handle, I asked for a foot or two, or any piece thereabouts. So we go into the shop and he picks out a piece of cold rolled. I'm thinking- whatever- and I spy a couple other pieces that could be useful. I gather them up, and he throws on another piece or two, saying it's only weight and nothing wrong with having some bits and pieces on hand. Ok, I got my hands full for less than five bucks, off I go.

I needed to make two 1/4 inch thick washers with a precise diameter hole in them. Fine, I face the piece- not so easy machining, finish looks rough- I drill near to size, hmm, sounded like rocks in the hole- bore it to size which goes well. That carbide boring bit I made from a broken burr is one of the best cutting tools I have. Anyway, I finish the hole to fit the stud to about a half thou of play and clean it all up.

I make two the same. Then I need to remove a pie shaped piece from each one, so off to the bandsaw. I start in following a mark, and when I get close to the center hole, the cutting gets tougher. It goes though, but backing the piece out from the blade it seems tighter than it should be. Hmm. I finish removing both pies and debur, then test the stud again.

It's a no-go! I shouldn't be surprised- the fact that the first cut closed up slightly should have rang a bell, but maybe I was tired.

So here I am, using the stupid piece of cold rolled, knowing that it's got built-in stresses and that I have to cut across the cross section- and knowing that's why I said no to cold rolled in the first place. I'm surprised though that it hardened up where I bored it. Is that something else to be expected of cold rolled, or maybe what I got was some mystery metal?

Machinist-Guide
02-04-2010, 01:37 AM
CRS shoulden't work harden at all. Sounds like you got some mystery metal.
D-2 tool steel among others will work harden easily