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Joined: Jan 2002
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Sidelock
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I never understood from Oscar's articles that the crucible should be nearly airtight. Did I miss something? It was my understanding that the increasing heat would drive out any oxygen that is within the crucible, and that a loose fitting top was necessary for this to happen. I have seen some beautiful colors produced with the oven and crucible I now own, and it isn't even close to having a tight fitting lid. ????????

SRH


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I think 'nearly' leaves some wiggle room. It's probably not a bad idea to be able to get the cover off quick when it's time to quench.

I don't know if heat would drive the O2 out, but it should be consumed when the little bit of it in there gets burned up with the charcoal. I'd think the pressure build would be potentially dangerous if the crucible was air tight. I think Ken's pop he mentioned was an inadvertent air tight seal.

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i have colored a lot of parts, i have always sealed the lid with furnace sealant,i put a piece of paper to burn and use up oxygen i put charcoal in and add bone charcoal and layer it,i ran air to have constant bubbles to break up the steam envelope.i ran my kiln at 1200 and depending what i had in my crucibles allowed time to get everything up to temperature. when i quenched i pulled the pack out knocked the lid off and dumped it into the tank.if you made you charcoal and its wet it will get scale.or if you dont cook the bone charcoal enough. that's all i got. mc

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So I'm still trying to improve the color case hardening procedure that im doing and have some more questions. At what time are yall starting the time for the parts to soak at the 1350 temp. Is it when you visually see the crucible with a dark cherry glow or when the door is shut and the furnace is building up temp. I usually cook the parts for the one and a half to 2 hours before I drop it to 1150 before I quench in order to prevent warpage. I start the 2 hours when I see the crucible is glowing. Is this too long?? I am still getting some side plate warpage where the fingers of the side plate attach to the receiver. The receiver does have spacers to prevent warpage but still does. Does anyone use lower temps? Thanks Hereford

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Ive been doing CCH in the shop for the past 15-20 years, and Ive been researching it for longer than that. Keep in mind that case hardening via bone char has been around for a loooong time, and was actually a commercial hardening process; everything from locomotive parts to delicate measuring instruments look at Starrets early squares (beautiful Colors), Ive got mid 1920s tap wrenches with gorgeous CCH. Pre WWII bone charr case hardening was well known and well established.

With that said, I dont think anyone will get original colors, for a variety of reasons, although I can get very close to Winchesters colors. OBTW, I do have Winchesters CCH formulas notice its plural, meaning they had different processes/formulas for different parts.

Here are some of your challenges:

Case hardening/Quench temps: Back in the day they did true case hardening, meaning the parts were quenched at 1600 degrees +. At those temps the metal will move. Winchester experienced a high warpage/cracking rate, and in 1903 stopped CHH. A large company like Winchester or Marlin can absorb a certain failure rate Can you?

Virgin Steel: Ive had the steel analyzed, its a very low carbon steel. Each time the steel is case hardened, carbon is added to the steel. The more carbon in the steel, the higher the chances of the steel warping/cracking.

Wood/Bone ratio: Different ratios will produce different colors/look.

Bone Char: I suspect pre-1900 the bone char was buffalo, today its most likely sheep imported from Scotland.

Water temperature: Water temps have a significant impact on colors, I suspect they used well water. Ground water temps vary across the country, water temperature is 2 to 3F above the annual mean temperature of the locality, because of this, well water in Mass is significantly colder than well water in Florida.

Shall I go on?

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Hereford

Do you mind sharing your oven plans and specs and general set -up.

Many thanks.

Travis

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I actually spent about a year developing my process for repeatable and reliable results. I would take 1/8 inch flat stock and surface grind them so that they were dead flat. I would then CCH them changing one variable at a time checking for colors and warpage. Sometimes up to two quenches a day; so a lot of time, money and energy went into setting up my system.

I remember talking to Oscar Gaddy about this, our first conversation he chuckled.. Told me not to do it . After a while he was quite helpful.

My set-up is a standard ceramic kiln, generally they can be had cheap on the secondary market, some bored housewife tries pottery for a month or so then gets tired of playing. Ive got four kilns in my shop all from the above.

I use a digital kiln controller on the kilns, good ones are not cheap, but it will maintain the temp +/- 2 degrees. The first one I bought, something like $400 15+ years ago, now I just build my own using inexpensive PID controllers.

My crucibles are inch stainless steel, Ive designed my quench tank system where the lid is removed and the crucible drops to a pre-determined distance from the water all in one movement. Again..consistancy.. Always the same each and every time.

Charcoal is mixed using a concrete mixer.

I keep 4 standard wood/bone ratios on hand; one for bold bright colors, two different mixes for Winchesters, and one for Colts.
Lots of variables in getting colors: Water temp, quench temp, wood/bone ratio, bone char size, blocking, drop distance between crucible and water, quantity of O2 in the water etc. And even then there are no guarantees one side of the frame may only have browns and blues, the other side looks like Picasso puked on it all the colors of the rainbow.

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SKB Offline
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Originally Posted By: Mike Hunter



Shall I go on?



Well yeah.....

How about some pictures of your crucibles and quench set up?


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It is a basic rectangular design that is 13in deep by 9in high and 9in wide. Used the brick to build structure. All encased in a steel/aluminum shell that I used all thread to compress. I used 2 coils and heat temp wire and connectors that I ordered from some foundry place off a blade forum a year or so ago. Pid, box, thermocouple, ssr's, etc I ordered off ebay in a kit for 220 application. Isn't pretty and may go back and add a few safety switches etc but works as intended. I dont have the wiring diagram any more but my pid actually had a diagram that was basically identical to how I wired it.

Thanks for the explanation Mr Hunter. Your work speaks for itself and I greatly appreciate the input. Images of the crucible and quench setup would be very informative.

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Originally Posted By: SKB
Originally Posted By: Mike Hunter



Shall I go on?



Well yeah.....

How about some pictures of your crucibles and quench set up?



Hummm. Gots about a year, and a bunch of $$$ developing my system; and what I mean by my system I know how DTR does it, Ive seen how Ballard used to do it (back when they were in Cody), I know how Winchester and Marlin did it, but my system is pretty unique from what I have seen out there, I would like to keep it that way.

Besides, its pretty simple concept; all you gotta do is dump some 1600 degree parts into a tub of water how hard can it be  The fact that I can do it in a t-shirt and flip flops without getting burned makes it a little different.

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