Heat treating S&W revolver parts

So S&W revolvers have case hardened ignition parts. In this question I am talking about older revolvers. Everyone says just replace parts, do not touch anything. Firstly it's a no go, parts are not a direct drop in for me, some places needed proper mating. Secondly in order to be super smooth mostparts bad to be adjusted polished, mated like a clockwork. Obvious keep away places are SA hammer notch and associated sear surface on the trigger (though one side had to be stoned on the sear to keep from hammer pushoff). I learned a ton during the build process and it was a very rewarding experience. Resulted in super duper smooth like butter and lite trigger pull in both SA and DA. Wore in parts with about 200 clicks and a bit of range time. All works wonderful.

Soooo question:
I made sure that case hardening is kept where it is supposed to be, but removed a lot on long surfaces with plenty of engagement. Now that the gun is slightly worn in to my liking I would like to "seal the deal". What would be bad about actually hardening the parts with proper thorough heating, quenching and annealing? I understand that the hammer may become more brittle, but there is plenty of meat to support the force.   What about trigger? Has this been done before, I cannot find sources?

I doubt that you damaged anything by going through the case hardening by just polishing up some parts.

Oh I am sure I did not. Main thing is not to mess with the hammer SA notch and leave trigger sear nose at least one side (inside) hardened.. rest of the parts are wide flats that are not an issue. I just want to lock everything in to prevent any further wear as I love it the way it is. May be a silly idea, it will take more rounds than I will shoot to wear things out, but heck why not? I see everyone saying to be careful not to mess up the hardening, but no threads on re-hardening. Not exactly a hard or very technical thing to do. Torch - oil quench - oven for few hours.

I did remove plenty of material from some (safe) surfaces ))  Some wouldn't work otherwise, some wouldn't smooth otherwise.

Brownells Kasenit?

I'd be more worried that whatever heat treating I did would affect the original hardening on the important bits.

I also have no idea what the material is, a plain carbon steel or an alloy. Is the CCH functional or just decorative?

Hmmm interesting, but not sure this is a right application. If I understand it correct the Kasenit carburizes plain and low carbon steel. Else it's null affect on carbon steel parts. From what I know Wesson parts are carbon steel, no?

CCH on SW revolvers is definitely functional, but they probably add salts to decorate it in the process.

Colors usually come from pack hardening. Salts, or gas, will case harden but leave the surface clean or grey.

Carbon steel can be anything from a smidge more carbon than ductile iron, up to 1% or more which will harden thru to glass hard

Tripscape wrote:Not exactly a hard or very technical thing to do. Torch - oil quench - oven for few hours.

You'll end up with parts covered in carbon scale unless done in a controller inert atmosphere.

Another question is do you want to retain the colors? Salt bath nitriding will surface harden it.

Nah, not caring about colors and any scaling can be removed. BUT, it can also change dimensions on parts which are very precise in mating.

You might consider leaving well enough alone, about 35 years ago I had a trigger job done on my 17-4 and the smith polished the surfaces of the trigger and the hammer, there is no case hardening color left.  I have put at least 10k rounds through it and countless dry firing cycles and there has been no change in the pistol or any detectable wear.  That being said I do wish the case hardening finish was still there.

Thanks. I am sure it will be.ok for many thousands of shots, but I guess overprotective of my work)). The question is more hypothetical of why no one talks about re-hardening when there are methods available.  Well, next time I see well priced parts I will grab them, mate and re-harden. More as a science project.

One thing to consider, the act of hardening itself changes the dimensions.  Even without distortion, which is also potentially possible with re-heat treating.  So case hardening can be “deep” or quite shallow and without doing a complete metallurgical work up, can be hard to identify.

All that said, pistolsmiths have been doing “action jobs” on S&W revolvers for decades.  Most of these lasted a very long time, so the “case” is deeper than it may seem.  I wouldn’t worry too much and enjoy the heck out of it.

I agree totally with  Wobbley. Any time you get steel hot enough to harden, dimensions will change and/or warp.
Also, just  because the color is gone doesn’t mean the hard case is gone. 
One more thing, high carbon steel does not need Case hardening powder to harden, it only helps on low carbon steel. All steel has some carbon in it hence the name carbon steel vs stainless steel. High carbon is considered to be anything above 0.5% carbon. The higher the carbon, the easier the steel is to harden and the more brittle it can become. High carbon steel must be tempered after hardening to make it tougher.

WesG wrote:I'd be more worried that whatever heat treating I did would affect the original hardening on the important bits.

I also have no idea what the material is, a plain carbon steel or an alloy. Is the CCH functional or just decorative?

Totally agree with the fear of heat and steel. As you rightfully asked, what is the steel?  Well, heck if I know and I doubt if anyone outside of S&W knows. And then, if it is a very older pistol, like 70's and earlier, I doubt anyone at S&W knows, or there is anyone alive who knows.

Sometime else, S&W owns their own technical data package and is free to change anything or everything as they want. Therefore it is very possible that hammers and sears varied in steel composition as S&W evolved with the times, or simply purchased steel from a different vendor.

I am of the opinion that the surfaces were case hardened, but the interior was kept as soft as possible. Increased hardness means lower fatigue and impact life. What I read, on gun parts, was getting the right heat treat on the right area was extremely important. Factories also have access to equipment that we minions do not. Maybe you could figure a way to heat the sear surface with the rest of the hammer under water.

Unless you have to, I would recommend not putting heat to anything. And if you have to, call S&W and see if they have parts still available. I think their cut off is around 1990. Anything earlier and you pound sand. Then you have to buy bunches of hammers and sears from used guns and hope one combination fits.

So the way I see it is that in the old world it would be cost effective to case harden because it does not change dimensions on parts. This way you work/tool soft part and harden just the outside in the end, instead of machining an already hardened part to right tolerances. As long as the steel has a good amount of carbon content the hardening process should be fairly same, and with hand smithing the part can be properly fit after hardening. I don't know about the mass and stress on these parts. Arguably trigger can be wholly hardened with no issues. I can see how it may be beneficial to keep hammer softer on the inside. Another question is how hammer batters the frame. You don't want it harder than the frame where it lands. After some consideratiin I think I will obtain at least an extra trigger and try to harden it, because why not? There are 4 critical contact points on SW trigger, only 1 HAS to be hardened, but having all hardened will provide extra longevity. Will stay away from hammer, the question of frame batter bothers me more than anything else.  Will do this experiment when I have some extra time, stay tuned.

Oleg: (and anyone else)…

Case hardening will change the dimensions, but possibly not as much as a through hardening steel.  The fundamental reason to case harden parts was to improve wear resistance.  There is a limited application of adding a “high” hard skin with good toughness, but there is a degradation in fatigue resistance if taken too far.  Lower carbon steels are/were easier to machine into complex shapes using high speed steel milling cutters in conventional machining equipment.  “Color” case hardening is as much a decorative process as a mechanical one.