How to do Color Case Hardening


Tom,
First off let me say WOW! Nice work and holding true to the Stevens level of appearance, kudos my man. IRT the color case hardening I found packing the part in a mixture of hand ground dry cow or horse bone, (my preference being the latter) and Hickory wood charcoal dust gives the richest most colorful spectrum Also the pattern can be varied by how you quench the cherry red part, every manufacturer used a different method Stevens would randomly use a jerking motion while quenching their parts. Others would agitate the quenching medium with bubblers or simply by hand. Also the jury’s out on whether you should have a skim coat of oil floating on top of the bath, I’ve tried both with no apparent differences noted. One note of caution there tends to be warp age to some of the smaller thinner items ie the hammer and thinner areas of the receiver at times so expect some refitting of parts and trueing up the receiver again

Looking forward to seeing this puppy doing range time. Keep up the quality work!
 

Tom,
First off let me say WOW! Nice work and holding true to the Stevens level of appearance, kudos my man. IRT the color case hardening I found packing the part in a mixture of hand ground dry cow or horse bone, (my preference being the latter) and Hickory wood charcoal dust gives the richest most colorful spectrum Also the pattern can be varied by how you quench the cherry red part, every manufacturer used a different method Stevens would randomly use a jerking motion while quenching their parts. Others would agitate the quenching medium with bubblers or simply by hand. Also the jury’s out on whether you should have a skim coat of oil floating on top of the bath, I’ve tried both with no apparent differences noted. One note of caution there tends to be warp age to some of the smaller thinner items ie the hammer and thinner areas of the receiver at times so expect some refitting of parts and trueing up the receiver again

Looking forward to seeing this puppy doing range time. Keep up the quality work!

Thanks Marlin,

Obviously I'm not quite ready to do any color case hardening yet, but hope to be soon. I've been looking around for info on CCH and this seemed like as good a write up as any. My Favorite isn't a direct copy of the Stevens Favorite. It's sort of my interpretation of it. I've made several internal engineering changes to make it easier to build without the need for castings, so some parts won't be interchangeable with the real thing. Call it artistic license if you like.

I've read about some of the techniques you describe and look forward to experimenting with them before I tackle hardening my receiver.

Thanks for the tips.

BTW, I just caught the pun in my original post and it truly was unintentional. :eek:

Tom
 
My Starrett 711 DTI looks like that. Would it have been colour case hardened? I was worried when I got it - I though it had been abused or left out in the elements.

Lol. Yes, Starrett color case hardens some of their tools though I doubt they would see the humor in your description of their finish. :rolleyes:

Tom
 
Hello,
I am new to this site, but found this thread while looking things over. I actually wrote the tutorial for the Home Model Engine Machinist forum that was linked at the start of this topic. One thing I would caution about the Marlin thread (I was also on that forum many times in the past) is that the person who did this work was quenching the receivers at a very low temperatures, i.e., 1250 F. I do research in casehardening at the University of North Dakota and have done fairly extensive testing on this process over the last five years and the low temperature issue frankly disturbs me.

While there is going to be some difference in hardness, in my opinion, you should never quench below the critical temperature, say 1370 F (varies), if you want to actually harden the surface. Strangely enough the colors are oftentimes better at these temperature ranges under critical, but hardening is superficial if at all. This is not good if the original design specified a hardened surface. Of course, the reason that some like to do this is not only the pretty colors, but also the fact that the shock at these lower temperature ranges is considerably less than it would be if quenching took place above the critical (higher) temperature range. Consequently there is probably less chance of metal movement and thus reduced risk of damaging the receiver, or having to spend considerable amounts of time hard fitting components afterwards. Frankly I block everything I care about and expect to have to do some post fitting when moving parts are involved. I would not shy away from this task at the expense of a properly hardened part.

I rarely, if ever, caseharden parts much under 1425 degrees F and prefer to soak them in the 1450 range knowing full well that the pack will lose temperature between the time it leaves the furnace and can be delivered in the quench tank. Carbon absorbs faster at higher temperatures, but quenching above 1500 tends to produce very dark colors and above 1600 they pretty much dissappear altogether. This said, a lot of industrial carburization takes place in the 1600 plus range. I have soaked parts at higher temperatures and than dropped to low temperatures for the quench with some success however.

I have never had any problem obtaining very vibrant colors with my process and rarely do much more than wrap the parts in soft iron wire before placing them in the crucible. My standard mix is 50/50 wood/bone and either tap, or distilled water. We have used oil skims and various admixtures in the quench and also run air lines, but frankly, plain old cold tap water freshly poured does as good as anything. Filling a container shortly before the quench allows proper agitation which gets the oxygen content up to a point that you need and the wire creates disturbance enough to give you the spectacular patterns you are after. The wire also helps hold the charcoal mixture in contact with the workpiece for a longer period which also helps with the colors.

If anyone has any questions about the process I can be reached at: ajohnson@business.und.edu.

Regards,

Alex Johnson
 
Thanks for the comments Alex, it's good to get information directly from the source.

It sounds like the guy on the Marlin thread was more interested in color than hardness if he's quenching that low. I would rather quench for hardness and take whatever color I can get. My Steven's project isn't quite ready for hardening yet, but it's getting close. I need to get over to Ebonex and pick up some bone charcoal, it doesn't seem to be available anywhere else unless you want to pay a fortune for it a Brownell's.

Tom
 
Receiving a good deal of information regarding the Colour Case Hardening process from the posts is much appreciated ...still there are a few questions I need to ask...keep in mind I have zero (nothing) practical experience with cch ..these questions focus more on the chemical processes...maybe a metallurgist will be able to provide some insight?... ..but:

1)In which sector are the colours (tan,cobalt blue, hue, straw ect) obtained or created...in the pack -compound or in the quench tank ...when are these colours created?

1 a)How are these colours created...which chemical process take place?

2)What ingredient can be added to create a specific colour? more cobalt blue or hue colour? Where (into which ) do you need to add the specific ingredient to attain the sought-after colour? quench tank or pack composition( bone -charcoal/charcoal)?

3)Which added ingredient will give you what colour?

Regards

Gert
 
The American Custom Gunmakers Guild has a video for sale on their website concerning Color Case Hardening and Nitre Blueing:

http://www.acgg.org/index.php/resou...997-seminar-1-color-case-hardening-nitre.html

The cost is $35. I have no idea what it covers or if it is even any good, it's just something I ran across recently.

Incidentally, if you haven't been to their site it is worth checking out. They have a number of resources available on a variety of subjects and the free sample (PDF) copy of their magazine "Gunmaker" has lots of great tips.

http://www.acgg.org/

Randy
 
The very best source of information on Colour Case Hardening can be found here :-http://www.marlin-collectors.com/forum/viewtopic.php?f=21&t=3732&sid=fff443322de44ac6480bdfe492c43a25
The thread runs to 30 pages and it takes a while to real all the pages and digest the information. Unlike many so called 'Experts' the writer actually shows his results and the methods of obtaining them. The two part article by Oscar Gaddy is interesting but very much out of date. There is far too much hocus pocus written about CC Hardening. Some of it makes Shakespeares Witches in Macbeth seem to be modern scientists. Just as an aside 'Wing of Bat and Eye of Newt seem to make the finish too green' lol.

Harry
 
Thanks for the comments Alex, it's good to get information directly from the source.

It sounds like the guy on the Marlin thread was more interested in color than hardness if he's quenching that low. I would rather quench for hardness and take whatever color I can get. My Steven's project isn't quite ready for hardening yet, but it's getting close. I need to get over to Ebonex and pick up some bone charcoal, it doesn't seem to be available anywhere else unless you want to pay a fortune for it a Brownell's.

Tom

So I read you entire thread and you are the reason that I found this website AND the reason I joined also!!! I wanted to see how your Favorite turned out as I am in the process of converting an 1894 Favorite that was originally chambered for 32 Long to 17 Mach2. I have relined the barrel and relocated the FP in the breech block so that it hits the rim of the 17 Mach2 correctly, but I am wanting to beef up the breech block pivot screw and that was the specific thing I was wanting to look at on your build. Very impressive machine work on that receiver by the way!!!
I'm primarily over at RimFireCentral and either on the Mossberg or Hunting forums. But I did some work on a Stevens Crackshot that had seen better days and in researching info for it I discovered the Favorites and I decided that I should have one!!! A member of the Stevens/Savage forum was able to tell me that Stevens case hardened their receivers according to some original literature he has, which would certainly explain why the threads in the receiver were able to reform the threads on a new breechblock pivot screw that I made out of a grade 5 bolt. So since the receiver is case hardened I have to anneal it so I can work on it properly, which means I need a heat treat oven, so I have to figure out how to fabricate one of those!!! I've been researching that for a while so I think I will be good on that, but now I find this info on CCH and I really like the looks of it. I will not be able to remove all of the dings and dents from the receiver but now added to the list is to CCH my Favorites receiver even though it is a very well used receiver with how shall I say... lots of character marks!!!
Well the whole point of this response was to see where you were at on YOUR Favorite. Is it CCH yet??? If so any pictures???
God Bless, Frank.
 
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