Quote:
Originally Posted by ed good
justin: the particular gh that you are referring to had it's receiver recolored by ed lander, an old time gunsmith here in nh. old ed has been a full time general gunsmith since he came home from service in ww2, in 1946! imagine having the services of a gunsmith with over 60 years of experience! we in northern new england are lucky to still have him around to work on our guns.
anyway, he uses a low heat chemical process to recolor shotgun receivers. he uses different chemicals to simulate different factory receiver coloring, depending on the brand and age of the gun. for example, i have a late ithaca 20 ga nid, that old ed also recolored the receiver. it is very well done and is close to ithaca factory work of the period.
unlike the high heat bone charcoal process of recoloring shotgun receivers, old ed never heats a shotgun receiver hot enough to reach critical temperature and thus altering the original factory heat treatment of the receiver metal. keeping the heat below critical temperature avoids the well known problems associated with after market re heat treating of shotgun receivers.
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Ed, I'm sure that 'old ed' is a good guy to have when you need something fixed, and it's nice to know there are still some old-timers around, but I think he has either not explained his process to you, you've perhaps misunderstood him, or, he's doing little to no good to guns he performs this 'low heat' process on.
Steels, whatever their specific metallurgy, have 2 critical temperatures, logically referred to as the lower and upper critical temperatures. The temperature necessary to carburize, which is what case-hardening is, is above the upper critical temperature (roughly 1650 F for .20C steels) Yes, this is a temp, if in the hands of an inexperienced person, will cause warpage, but it is necessary to to get the contained carbon into solution, and add carbon from the packing material. The skill comes in packing, to avoid deformation, and quenching, or rapid cooling from the normalizing temperature to retain the grain structure. The mechanical properties are not in a usable form; even though the UTS(ultimate tensile strength) is high, yield strength will be so close to UTS, that the other two properties, Elongation, and reduction of area, are nearly non existant. Read "Brittle".
a single, or often necessary, a double temper treatment is necessary for maximum, over all, physical properties. This involves raising the parts again, above the Lower critical temp, but well below the upper critical temps.
Whether 'old ed' is taking his parts above the lower critical temps to get these colors, often from 'quenching in oil' I can't say, but any subsequent heating risks simply annealing to a near dead soft condition. I'm sure I'm not alone in wanting to more than just 'simulate' colors of a proper heat treatment, and have it done properly. There are several good craftsmen doing excellent work. What may differentiate them to many is the resulting colors, but these guys wouldn't risk hard earned reputation simple to 'simulate' proper work.
01-02-2012, 02:47 PM
:nono :
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