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,
John