doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Case Coloring Question

2-piper, the information I wrote about was from the 18th Edition of the Machinist's Handbook. As far as how the "old masters" did it, most handed down until they found what they liked. It's a shame that most of it is gone or kept secret.

There is a good article in "Home Gunsmithing Digest" by Tommy L. Bish, published 1970, that goes into detail on how to case-harden, case-color parts.

As far as you saying they would invest that much time in the process because labor was cheap, I disagree, labor is still expensive, no matter then or now, $.20 /hr. then to $30.00 /hr. now, still relevant.
I know that L.C. Smith's parts were all hand fitted, and their case-hardening-coloring was some of the nicest around. So I cannot believe that that much time was invested in the process. I've never tried to file a case-hardened-colored piece to see if it was truly surfaced hardened. Maybe someone could tell us if they did. David

JDW = be assured that guns were case hardened for parts durability. Color was a byproduct. It is easy to forget that low carbon steel is pretty soft stuff. As far as gun design goes, case hardened low carbon steel is a pretty satisfactory material. While not as desirable as modern alloys, it still does a good job.

Oscar Gaddy's DGJ articles/research seem pretty definitive to me. Extremely well done including photomicrographic work. His directions work well also-mixes with more bone charcoal(up to 50-50) favor the blue/green end of the light spectrum, lest bone(10%), favor the red/orange end. Best, Dr. BILL

I have tried cutting through new color cased pieces that were merely samples to find that most were hard enough that a momax steel chisel would break & skid off the steel surface. Needless to say, these same samples would resist being filed. FWIW, Ken

The process essentially as described in Machinery's Handbook, with the exception of adjustment of the carbonaceous mat'l for color, is what is described in W W Greeners book "The Gun" & is also given by an L C Smith engineer in the "Plans & Specifications" book. Many of the processes involved in producing these old classic guns from rust bluing, oil finishing stocks etc were all time consuming. For about the last 50 years I have read at every turn that the price of labor (Brought about by the labor unions, of which I was a member) was what killed the double gun in America. It was of course many more aspects involved, not the least of which was the desire for "FirePower". That time consuming method of case-hardening though was indeed the method by which the old classic gun-frames with color were finished. Chemical finishing of an alloy steel simply for the purpose of producing clor is a late phenomenum.
Miller

The one LC I tried to file was hard as a wedding....well suffice to say, it wouldn't cut with the file.

Case colours are a very pleasing addition to any gun.The prime purpose of case hardening is to provide a hardened wear surface on the action, fore end, lock plates and certain pins and screws.The process is controlled so that the penetration of the hardening is limited to.005 inch approx; at the same time care is taken not to diminish the strength of the core metal.
Unfortunately in the process of recase hardening,increased case depth [carbon penetration]may result and the strength of the action of the gun may be significantly reduced.
Some years ago whilst reviewing restoration of a best English gun with a reputable English gunmaker, the issue of recase hardening was discussed.
The gun maker said they would not undertake the work unless I accepted full responsibility if the gun failed in reproof!
To illustrate their concern, he produced the action of a best London S.L.E. That had failed reproof following recase hardening.The failure occured at the junction of the water table and the vertical breech face, excessive carbon penetration was evident. My gun was hot recase hardened!
Recase hardening is currently in vogue. My question is: What process controls are currently used to avoid the problem described above?[ie:excessive carbon penetration and reduction in ultimate strength of the core metal]

Roy, Very good point. I think you hit the nail on the head. If the receiver, and if it has sideplates were originally case-hardened, had the case colors, and the colors wore off, the case-hardening would still be there. Now originally, the depth of the case-hardening was .002-.005. Re case-hardening the piece would definetly do something to the metal, what I don't know. Maybe there is a metallurgist out there that can add some light to the picture.

According to a letter from an engineer for L C Smith at Hunter Arms (written 1949) the procedure used there was to pack the parts in a crucible containing 3½ parts charcoal to 1 part charred bone. This was placed in a furnace, heated to 1600°F & held at heat for 2¼ hours. The crucible is then direct quenched into a tank of running, cold, soft water. I have in the past had access to a time/penertration chart for carburizing depths but do not have one here at home (retired). I would however expect this to give a minimum penertration of .010" to the case. Adding carbon to a low carbon steel of course does not reduce it's ultimate strength, but increases it. What can happen though is (as in the early 03 Springfields) the steel can be strong, yet brittle & unable to stand a "Shock". I am not up enough on this to say, if in "Re-Casing" penertration is accumulative, ie does it pick up where it left off, or does it have to start over. As this outer case is already carbon rich, I would assume it would immediately upon reaching temp begin to penertrate deeper, but this is simply a guess. I have always had great reservations about having a frame re-cased.
Incidently Cyaniding is normally limited to depth of less than .010".
Miller

2-piper, thanks for the information. In the article from "Home Gunsmithing Digest", that I mentioned earlier, it also stated about packing the parts in a crucible of steel and doing the same thing. It did not go into detail on re-doing case-hardening on the same part.
I have to go along with Roy and say I would be very skeptical about recase-hardening now that I have heard about his experience.