John Murphy of Columbine Bicycles graciously agreed to let me send these comments of his on stainless. I think most of us can sympathize with his comments about the number of emails received as a member of the CR list. Lou Deeter, Huntsville AL
Thanks for the update. I signed on to the Rendezvous, and the next day
had about a hundred emails on my machine and literally "freaked out". I
desperately got out of it as I did not care to chat about every nut and bolt
ever produced. I'm sure it has some good points, but I don't have any spare
time to delve into it, and I don't take surprises on my computer well.
As to the stainless lugs etc go, I was the first person that I know of that used them in this country. In 1979, we began asking Henry James to cast us up some from the same molds he used for the regular lugs. When they were cast in 300 series from the same molds, the shrinkage factor is drastically different due to the same crystalline issues that help make the 300 series so difficult to work with. We had to work with the shrunken lugs with several handmade tools that made the frames take a lot longer on top of the normal stubborness of the stainless. I was occasionally welding up stainless tubing to get to the final lug but if you want to do something really time consuming, that no one will really be able to appreciate, try to make blank lugs from stainless steel tubing. I also made my own stainless dropouts before anyone had a cast or laser cut version. I had them plasma cut from sheet and then I machined the sides to give raised faces etc. Actually not bad for work excesses. In about 1981 we got our first stainless lugs from Henry James and for about 10 years enjoyed an exclusive from him (partly because Hank did not feel they were a finished product with the shrinkage issue). The very first ones were from a carbon Martinsitic/ferritic type stainless 431 alloy. We preferred the 300 series, but Hank said that the casting house frequently cast in the 431 and found it easy to switch his waxes over to that line of casting. In a couple of years we were able to get the 304 and 316 castings. The 400 series is much easier to work with, not differing much from the carbon steel varieties. The problem with several of the 400 series is that many of them suffer diminished corrosion resistance in various conditions, intergranular corrosion problems more than the 300 series, and some are not even stainless until heat treated to a significantly hard Rockwell number.
Under a microscope or chemically, the 300 series Stainless steel is as much different from steel or 400 stainless as steel is from Aluminum. It can absorb vast quantities of energy, and is literally alive and can use the energy from forces in the environment to build strength, evolve, and change into the gnarlyest "carbide for breakfast" eating substance on the planet.
For instance, take a DT Revolution spoke. Starting life, the tensile strength of the alloy (I'm guessing close here) is around a pathetic 60K lb/sq.in.. The yield strength of the alloy is so low that it would void it's usefulness as a structural material for anything but a bottle cap. Enter pressure. The dies for drawing stainless take more abuse than any others, and usually you can see the scars on the dies in the stainless that you buy. The tensile strength from work hardening goes from that pathetic figure to over 200K, a nearly quadruple figure. Now there are other alloys from Bronzes and Aluminums and steels that work harden drastically when subjected to pressure, but you would be hard pressed to find an alloy that changed by that figure just from work hardening. Steels that have high manganese contents can do that, which is why the old Reynolds 531 was such a respectable metal for the cost, Manganese is cheap. Anyway, another benefit of work hardening is that it is essentially a forging process wherein the crystalline structure of the metal is aligned to the forces. A good analogy is stepping on velcro. Heat treating cannot really accomplish this part of the hardening benefit.
In terms of working the metal with tools, it sees the tool as a hardening device. Unless the tool is really sharp and you use agressive feeding to the limits of the strength of the tool, the metal will harden to at least the hardness of the tool, and you'll never get through it. In other words it forms a hard layer just ahead of the shock wave from the tool, and somehow you have to stay ahead of that process by getting under the layer. Easy to say. Some of the carbide tools I use on the hardest tubings made and at times Titanium and will last years of careful usage at that level of stress will not survive a single cut on the various 300 series alloys I use. It's just that tough. A hammer blow to a 60K piece of metal will render it almost impossible to drill or saw at that spot. With a machine tool like a lathe, you can apply more force, but with something like a jewelers saw, you can only break them then replace them.
Beginners will discover the 303 alloy. It was designed to make machined parts with nearly the generous corrosion resistance of 304 and 316, but without the bratty tool crunching properties. It contains Selenium and increased Sulphur to obtain these properties but is not brazeable or weldable except under certain conditions.
Anyway, if it seems like Stainless steel is a brute, it's nothing compared to electroplating, the alternative for bicycle britework. We started plating in 1978, and I dismantled the electroplater last year. I can't even begin to elaborate the heavy issues that come from that stuff. Some of the most disappointing moments of my working life come from the surprises derived from plating. It looks great when it comes out of the tank, but it's hard to justify the surprises for the cute look coming out of the tank.
Well, gotta go make sparks n dust. Thanks again for the update.
Regards n Tailwinds,