Saturday, December 19, 2009

They say the heart of rock and roll is the beat...

“They say the heart of rock and roll is the beat...” Huey Lew and The News

I was thinking about that that song other day. So what would be the heart of a knife?

All knives have common features, handle, blade and edge. The handle and blade are easily decorated, but not so much the edge. If you turn a knife into an object of art, is it still a knife? I want to say yes, but if its form over whelms its function does it retain it’s core identity. Perhaps it’s the potential. The objet d'art knife still can cut or stab, but doing so would ruin its appearance and function.

I was at a knife auction and several lovely stag handled Hubertus autos were auctioned. The blades were engraved and etched; they were absolutely beautiful. I didn’t bid on them; the blades didn’t have an edge. That’s right, unsharpened blades, or if as I prefer call them, spatulas. I’m not sure you should even call them knives. No edge, no knife, seems simple enough.

So the edge is the heart of the knife? I think so, but it isn’t the soul. The edge depends on the steel. Companies have developed many proprietary steels like ZDP-189 or Sandvik 12c27 for special purposes and niches. Other steels like 1095 and W-1 have been around for years. Any knife discussion group will have their share of steel junkies, all of which are jonesing for another fix of some steel reported to have mythical qualities. Kind of like a doper in search of the ultimate high.

What gives most steels the strength, hardness and flexibility is carbon. After forging or casting steels can become so hard, so brittle they are tempered. Tempering softens the steel at little by allowing a little carbon to go back in to solution.

It’s complicated. Carbon dissolves in molten iron like sugar in hot water, but let the steel cool and on the way to room temperature iron forms austenite and ferrite. These are different crystals of carbon and iron. Ferrite holds very little carbon and austenite a little more. But austenite hates itself and wants to change. Some time, most time it changes to martensite. It can hold more carbon than ferrite, but it’s brittle. Very hard, but very brittle, so brittle that the knife blade can snap. By tempering or heat treating the blade some of the martensite can changed into our old friend ferrite. The extra carbon? Even thro it has paid its bar bill, carbon has been reject by first ferrite, then austenite, then martensite and again by ferrite. Who would blame it if it develops a complex? The rejected carbon forms tiny ceramic-like clusters with a few iron atoms hanging around the property line called cementite. Don’t feel sorry for cementite, it forms the microscopic small teeth that let the blade cut.

I started thinking carbon was going to be the soul of the knife. I’m wrong; heat treatment is the real soul of any knife.

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