Pittsburgh cold heading plant

Tom's first-person visit as a young assistant professor — "you have never been through a plant any louder than that plant."

There's another process. Back when I was a young assistant professor, I went to Pittsburgh once and I don't remember why, but I went through a plant doing cold heading. Cold heading was developed after World War Two when someone learned that if I put a phosphate coating on steel — how do you put a phosphate coating on steel? You just dunk it in phosphoric acid. Is that hazardous? It's Coca-Cola, right? Coca-Cola is just phosphoric acid. So it's not all that hazardous. The other day a classmate of mine was here who used to go through a case of Coca-Cola a day, and he ended up in the infirmary with anemia, because he lived on Coca-Cola and M&Ms. Couldn't figure out why he had anemia. But if you phosphate-coat this — you take a wire, this is 3/8 inch diameter wire, phosphate coated, then put it in a stearate bath. Stearate — what's that? It's soap, same type of thing. Stearic acid, it's a stearate.

Tom's first sample collection. Eight-stage forming sequence: shear → size → backward extrude → deepen → flange → punch hole → knurl → thread → plate. Production rate 10–20/sec; phosphate-stearate ("soap") lubrication; deafening noise levels.

This was one of the first things I ever collected. I went to Pittsburgh to a firm — I can't even remember the name because it was over 30 years ago — and they were doing what's called cold heading. In this course we'd call it extrusion. Cold heading was developed after World War 2 when they discovered that if you took a piece of steel and phosphated the surface — and I cover this when I do adhesive bonding, because phosphated surfaces are how you prepare surfaces for adhesive bonding — you can take a steel rod and you can shear it. [Tom holds up the cold-heading sample sequence.] This is the sheared piece of a three-eighths inch steel rod. It used to feel soapy. Most of us have fingered this a lot for the last 30 years. This is the first sizing operation where they take that and squeeze it to size it precisely, put a little indent on one end. This is the next operation, where they actually start an internal, a backward extrusion, and they start making a deeper indentation. This is the next one where they go deeper and the thing is now getting taller. This is the next operation where they put a flange on it, a head on it. Then they have another operation — and this is the one I don't want you to lose, I've lost it a couple times over the years, I'm about to lose it again — this is the only piece of waste from this process. This is the hole they punch out of the middle of that flange. So this is what you end up with. These two go together, got a hole in it because they punched out that little ring. Then they knurl the outside, then they thread the inside, and then they plate it. And what is it? It's a machine screw insert with a knurl. If I'm a woodworker and I want to put my thing together with machine screws, I can use this insert and drill a hole in the wood, slam this in, the flange keeps it from pulling through, and now I can put my machine screw in and I have a good strong joint in a piece of wood furniture.