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color case hardening
- Thread starter robert bw
- Start date
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Any professional blacksmith knew how to case harden even 300 or 400 years ago. Anybody who does case hardening on a regular basis will end up with colors at times. Back then it was only a matter of finding out why they had colors sometimes and then not at other times. It never took long for somebody to discover why. But they tried to keep it a professional secret for economic reasons.
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I got my start in case coloring using the Brownell's stuff but the colors were rather drab. This was because I was using to much heat. Had good case depth but not much color.
I now use 1425-1450 for 1.5 hours,use a mix generally of 3-1 wood to bone charcoal and make sure the drop is no more than 1.5 inches from the quench water. I use a shutter lid system that causes the drop height to be very consistent. Gaddy taught that this was important to getting good color because it prevents any air from effecting the parts.
Colors began to improve after reading and trying Oscar Gaddy's suggestions on the subject.
I also picked up some info from an English four generation double gun builder (Browns Double Guns) that greatly helped.
One of the best tips I got from the English gun maker: after withdrawal from the furnace let the crucible set for two whole minutes or "rest" as he put it before dumping in the air-rated quench water. I think all this does is let the heat dissipate a bit, it sure enhanced the colors.
One to the techniques I experimented with and now use regularly is to sand and then bead blast the parts after finishing the normal clean up and stoning of all the parts.
This had the benefit of doing two things, it knocks down the bright gawddy colors that come out and it gives a bit of "knapp" for the oxides to attach themselves to making them last better in my opinion.
A good deep case and color will last surprising well if done correctly.
If they wipe off easily then it was not a very good job plain and simple.
Turnbull's case jobs don't come off very easily and he is probably one of the industry standards now days. But boy are they gawddy in my opinion!
I have seen guns many decades old that are used regularly and still have good colors. Actually when they get a little wear on them they begin to really look good in my opinion.
I now use 1425-1450 for 1.5 hours,use a mix generally of 3-1 wood to bone charcoal and make sure the drop is no more than 1.5 inches from the quench water. I use a shutter lid system that causes the drop height to be very consistent. Gaddy taught that this was important to getting good color because it prevents any air from effecting the parts.
Colors began to improve after reading and trying Oscar Gaddy's suggestions on the subject.
I also picked up some info from an English four generation double gun builder (Browns Double Guns) that greatly helped.
One of the best tips I got from the English gun maker: after withdrawal from the furnace let the crucible set for two whole minutes or "rest" as he put it before dumping in the air-rated quench water. I think all this does is let the heat dissipate a bit, it sure enhanced the colors.
One to the techniques I experimented with and now use regularly is to sand and then bead blast the parts after finishing the normal clean up and stoning of all the parts.
This had the benefit of doing two things, it knocks down the bright gawddy colors that come out and it gives a bit of "knapp" for the oxides to attach themselves to making them last better in my opinion.
A good deep case and color will last surprising well if done correctly.
If they wipe off easily then it was not a very good job plain and simple.
Turnbull's case jobs don't come off very easily and he is probably one of the industry standards now days. But boy are they gawddy in my opinion!
I have seen guns many decades old that are used regularly and still have good colors. Actually when they get a little wear on them they begin to really look good in my opinion.
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I haven't any idea of the internal temperature Jerry I just know the color is better and case depth is still adequate.
This method relayed to me by Robin Browns writings on how they do it at their shop was a great help in advancing my learning curve and it is time proven over four generations on fine double barrel shot gun production.
I doubt the internal temperature inside a couple of inches of red hot charcoal has dropped a hundred degrees in two minutes and I know of at least one fellow that has done many Marlin receivers that only uses 1350F before his drop.
I mostly do single shot rifle receivers and their various parts so this is primarily the area I have focused on.
This method relayed to me by Robin Browns writings on how they do it at their shop was a great help in advancing my learning curve and it is time proven over four generations on fine double barrel shot gun production.
I doubt the internal temperature inside a couple of inches of red hot charcoal has dropped a hundred degrees in two minutes and I know of at least one fellow that has done many Marlin receivers that only uses 1350F before his drop.
I mostly do single shot rifle receivers and their various parts so this is primarily the area I have focused on.
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Hi,
Of course you are making a trade off between depth and hardness of the case and colors. I experimented with different temperatures using a 50-50 mix of bone and wood charcoal, 90 minute heat soak, and room temperature quench stirred just before the drop. The drop was about 1-2 inches above the water. My crucible is a rectangular box and lid and the pack drops as a solid brick. I ranged the temperature in 25 degree increments from 1375-1600 degrees. The best blues and purples occurred at the lower temperatures. As the temperature increased, amber tones tended to dominate until they finally became grayish at 1600. I found that 1475-1525 were my best trade off temperatures for colors and hardness given my conditions of charcoal mix, heat soak time, and pour. I used an electric furnace with programmable controller so the temperatures could be set and maintained quite precisely.
dave
Of course you are making a trade off between depth and hardness of the case and colors. I experimented with different temperatures using a 50-50 mix of bone and wood charcoal, 90 minute heat soak, and room temperature quench stirred just before the drop. The drop was about 1-2 inches above the water. My crucible is a rectangular box and lid and the pack drops as a solid brick. I ranged the temperature in 25 degree increments from 1375-1600 degrees. The best blues and purples occurred at the lower temperatures. As the temperature increased, amber tones tended to dominate until they finally became grayish at 1600. I found that 1475-1525 were my best trade off temperatures for colors and hardness given my conditions of charcoal mix, heat soak time, and pour. I used an electric furnace with programmable controller so the temperatures could be set and maintained quite precisely.
dave
I have done approximately the same thing as Dave Pearson. I had the same results. I found that I had a fair degree of hardness at 1350° and a lot more colors. However I always try to quench at about 1450 to 1500. I do a lot of gold work and it requires a very close temp. control. The gold work will alloy out at anything over 1550° F
I knew a lot of professionals who quench at temps as low as 1250° because the customers are more impressed by the colors than they are at the hardness. The average guy doesn't even kmow how hard the surface is. With fine engraving the hardness is very important because the idea is to stop the engraving from wearing down.
MD is probably quenching at 1350 to 1250. and that will produce some fine colors and a acceptable amount of hardness for most people. There is another advantage of quenching at that low temp, Less warping.
I knew a lot of professionals who quench at temps as low as 1250° because the customers are more impressed by the colors than they are at the hardness. The average guy doesn't even kmow how hard the surface is. With fine engraving the hardness is very important because the idea is to stop the engraving from wearing down.
MD is probably quenching at 1350 to 1250. and that will produce some fine colors and a acceptable amount of hardness for most people. There is another advantage of quenching at that low temp, Less warping.
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I use a programmable furnace as well from Evenheat and have been experimenting with two stage heat soak.
The idea is to hold it at the higher temperature 1550 for 1 hour for more carbon infusion and reduce to 1450 for 1 hour, pull and let rest for 2 minutes and then quench.
I've gotten good results on several receivers with this method. I have a couple more Rolling block receivers to do in the near future and will use this technique on them.
I keep a 3x5 card file on the particulars of each change in technique and the results so I can reproduce it at will.
As Jerry points out less heat means less warpage or crack potential and better color.
I have also found that reusing the same quench water with a bit of new distilled water added along with pre-aireating of the water for fifteen minutes to a half hour before the quench makes brighter colors.
I use one of the fish tank micro bubblers that works very well.The bubbler also has the benefit of agitating the quench water. I cut the bubbler just before the drop as what is wanted is the dissolved oxygen in the water not the larger bubbles.
I also like to draw the temper after the quench at about 350 F for 1 hour. I don't know if this last is really necessary but I do it as a precaution against cracking in areas of a receiver with square mortise cut outs.
The hard skin of carbon infusion is under tremendous tension, I have read, after the quench and the anneal is supposed to relieve this somewhat.
The idea is to hold it at the higher temperature 1550 for 1 hour for more carbon infusion and reduce to 1450 for 1 hour, pull and let rest for 2 minutes and then quench.
I've gotten good results on several receivers with this method. I have a couple more Rolling block receivers to do in the near future and will use this technique on them.
I keep a 3x5 card file on the particulars of each change in technique and the results so I can reproduce it at will.
As Jerry points out less heat means less warpage or crack potential and better color.
I have also found that reusing the same quench water with a bit of new distilled water added along with pre-aireating of the water for fifteen minutes to a half hour before the quench makes brighter colors.
I use one of the fish tank micro bubblers that works very well.The bubbler also has the benefit of agitating the quench water. I cut the bubbler just before the drop as what is wanted is the dissolved oxygen in the water not the larger bubbles.
I also like to draw the temper after the quench at about 350 F for 1 hour. I don't know if this last is really necessary but I do it as a precaution against cracking in areas of a receiver with square mortise cut outs.
The hard skin of carbon infusion is under tremendous tension, I have read, after the quench and the anneal is supposed to relieve this somewhat.
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Yes, I use a snug slip fit to the major thread diameter, hollow round block in the barrel hole and another square block drilled full of holes in the mortise that retains the hammer and breech block.
I want the support but I don't want the massive heat sink effect of the support blocks.
I want the support but I don't want the massive heat sink effect of the support blocks.
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My first crucibles were made of steel for a vertical drop of gun receivers like Gaddy used but after trying them for a while and doing more research I found that the old gun firms like Stevens and Marlin used rectangular crucible boxes made of iron with loose lids and dropped the receivers horizontally, top first.
So I made some more stainless box type crucibles and now prefer them.
I think good color is easier to get with this method and the warpage is no greater, which was my primary concern before switching.
The loose lids are necessary for a couple of reasons.
1. They need to let the contents out evenly all at once during the quench drop.
2. They need to allow the carbonizing gas from the burning charcoal to escape to relieve pressure in the crucible.
I have at least half a dozen different shapes and sizes of steel crucibles now to better accommodate the various gun parts and to save on the expensive charcoal.
I do need to experiment on reusing charcoal after it's dried out from the quench to see if it will still work or not.
The hazmat to Alaska is frightfully expensive.
So I made some more stainless box type crucibles and now prefer them.
I think good color is easier to get with this method and the warpage is no greater, which was my primary concern before switching.
The loose lids are necessary for a couple of reasons.
1. They need to let the contents out evenly all at once during the quench drop.
2. They need to allow the carbonizing gas from the burning charcoal to escape to relieve pressure in the crucible.
I have at least half a dozen different shapes and sizes of steel crucibles now to better accommodate the various gun parts and to save on the expensive charcoal.
I do need to experiment on reusing charcoal after it's dried out from the quench to see if it will still work or not.
The hazmat to Alaska is frightfully expensive.
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I would be interested to here if any of you folks who mess with case hardening and coloring have tested used charcoal after it has dried from the quench.
I have noticed there is very little ash in it after I have reclaimed it and it looks almost like the fresh stuff with the exception of a bit of lighter colored grains I suppose to be partially ash.
I would expect that the phosphates from the bone and perhaps some of the carbon from the wood to be dissolved out but it just might be re-usable until it becomes ash.
I'm reasonably sure that is the reason used quench water helps make more vivid color because of the dissolved phosphates already in it from the previous charcoal dump.
Interesting subject and tons yet to learn!
I have noticed there is very little ash in it after I have reclaimed it and it looks almost like the fresh stuff with the exception of a bit of lighter colored grains I suppose to be partially ash.
I would expect that the phosphates from the bone and perhaps some of the carbon from the wood to be dissolved out but it just might be re-usable until it becomes ash.
I'm reasonably sure that is the reason used quench water helps make more vivid color because of the dissolved phosphates already in it from the previous charcoal dump.
Interesting subject and tons yet to learn!
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It most likely will not even come close to matching the other colors on the gun as I'm guessing they are cyanide cased not charcoal which looks nothing alike.
frogwalking
45 Cal.
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Here is a wonderful story of how to do it, with photos.
http://americanlongrifles.org/forum/index.php?topic=41026.0
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bubba.50
Barefoot Hillbilly
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jerry huddleston said:
I'd take that chance if I could find someone to do the job right reasonable. if it didn't work out the brass one would go right back on & all I'd be out would be a mildly costly Renegade triggerguard. that might give me the excuse to buy a pre-carve from Track or Pecatonica.
