Airweight J-frame: What parts case hardened?

D

dyl

New member
Hi folks,

I have a question. Given a S&W 642 or 442, what parts are case hardened?

Here's why: I did a very conservative smoothing out of the action with a rouge cloth, hard arkansas stone, brownell's action lube. I stayed away from the sear because I don't quite understand the angles involved and I thought the whole hammer was case hardened. I believe that for case hardened parts you do not want to remove metal if you can help it. Also barely smoothed out the corners of the rebound slide and barely polished it. I was afraid it was case hardened or something - but perhaps that was just a carbon coating.

I also slightly rounded the back edge of the trigger because it would pinch my trigger finger a bit.

Looking back I'm wondering what parts I would've been allowed to smooth as I please (within reason of course).

I once saw a youtube video where Nutnfancy gets his revolver smoothed by a gunsmith. That particular smith took an arkansas stone to the aluminum frame of the revolver as well as to the sear (he was really rubbing away) without a bench vise or anything to hold it steady.

Just seeing what you all think.
 
W

Whirlwind06

New member
I would think what you describe would roughly equal a shooting or dry firing it a couple 1000 times.
I think removing high spots is fine, mirror polish is not what you are going for.
 
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D

dyl

New member
and a related question..

Thanks whirlwind. I actually did both! (dry fire and light polish) still curious though, it helps to know and it may be applied for future projects.

So any thoughts about case hardening?

Are MIM parts safe or effective to polish? - I noticed the rebound slide was a dark color and barely touched it because I thought it might have a coating of some sort or was more/less than plain steel.
 
D

DPris

Member Emeritus
Case hardening's only done on hammer & trigger, unless you get one of the S&Ws with a case-hardened frame.
As such, you can stone engagement surfaces, just don't use a very abrasive stone & don't take a file to anything.
Denis
 
J

James K

Member In Memoriam
Actually, I think the answer today is none. Those parts formerly case hardened are now made by MIM and are hard all the way through. The color of the hammer and trigger is not case hardening; it is simply coloring put there to keep S&W's trademark in effect.

Jim
 
D

DPris

Member Emeritus
Let's put it this way:
True case hardening can be stoned & a slight amount of material can be removed in the process. Getting too carried away can remove material below the hardened layer.

Case coloring on MIMs can also be stoned, without worrying about getting through a hardened layer.

So, either way, on a new Smith or an old one, engagement surfaces can be stoned.
Least material removed is best.
Denis
 
1

10 Beers

New member
Case hardening is not a coating, you'd have to cut pretty deep to remove it. Basically you heat the metal to a dull glow and jam it into a bucket of nasty animal hide/hair (smells nice) which infuses carbon to a certain depth which can be quite deep. This is great for guns 'cause it doesn't change dimensions like other coatings.
 
M

mete

New member
There is no reason why a powder metal or an MIM part can't be case hardened . We were case hardening powder metal parts back in the '60s !!:p
I just tuned a 642 and I'm sure the hammer and trigger are case hardened .They reacted to stoning just like the earlier S&W revolvers.
If you decide to smooth things up -- DO NOT use DREMEL, NOR abrasive paper or cloth ,or any coarse abrasive.
ONLY USE fine ceramic stones and maintain all the original angles and don't round off any surface.
 
D

dyl

New member
Great! :) lots of good info.

Thank you very much. And as always I will not hold any of you responsible for any trouble I get myself into and will do my best to restrain the tinkering beast within me. :p
 
J

James K

Member In Memoriam
Case hardening is not a coating on steel, it is a change to the surface layer of the steel itself, but it is not very deep. The process S&W used went only to about 10-20 thousandths (0.010 - 0.020 inches), so removing it doesn't require going very deep. Case hardening (carburizing) dates back centuries, so it is nothing new.

The reason S&W stuck to case hardening was that it allowed a combination of tough, but rather soft, steel, that would not be brittle and could be easily machined, along with a hard surface that would stand up to rubbing contact indefinitely. It is almost impossible to wear out a case hardened S&W hammer or trigger; almost all that fail do so because of tampering.

MIM parts, on the other hand, do not require machining and are shaped correctly when made, so they are heat treated to be hard all the way through. They could be case hardened, but there would be no point. The coloring is simply a surface application for no reason other than preserving the trademark.

Jim
 
J

James K

Member In Memoriam
It doesn't take long at all, and I can say that from personal experience. Ten thousandths of an inch is a bit more than the thickness of two sheets of printer paper, and believe me, it is not at all difficult to take that much off with a stone.

And I am not sure S&W's case hardening always went even that deep.

Jim
 
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