Are all sears only "case" hardened?

[dyl]

I remember hearing how work on sears should be extremely conservative. Partially because the precise angles involved but also because warnings that sears were hardened on the outside only and soon you'd have push-off when worn down to soft steel. Does this apply to revolvers only, and only older revolvers at that? I assumed it was because there weren't any computer controlled processes / ovens like there are today so the easier way would just be to heat up a cheaper piece of steel and swish it around in a given media.

How about SA/DA semi autos? Like my Jericho 941F (made in the 90's) or my CZ 75 SP-01? Those sears are so small, wouldn't it be easy in a factory to heat, quench, then temper a huge tray full at a time? That way they'd be through-hardened.

Are sears still truly case hardened only? If so, why?

- by the way, I'm not planning on going nuts on my sear. But I did just purchase a beater SA/DA pistol, and if I was ever going to stone a sear it would be this one as Tanfoglio small frame / EAA witness fire control parts are compatible and plentiful.

 

[Scorch]

No, there are many sears that are through-hardened, but they are less common and more expensive. All S&W MIM parts (for example) are surface hardened and may last through years of normal use, but will wear quickly once you get through the hardened surface layer (.001"-.005"). Older Winchesters and Remingtons and Savages and H&Rs, etc, etc, were made of cast iron or mild steel and case hardened to give a longer-lasting wear surface on critical parts. WW2 GI 1911A1 sears and hammer were notorious for being surface hardened, and many people found out the hard way that they wear quickly after getting a "trigger job" from well-intended so-called smiths. Same with Mauser 98s, Springfield 1903s, etc, etc. These parts are case hardened, carburized, flame-hardened, etc, to give a hard, long-wearing surface. It was common because these were minor parts that would do just fine without making them out of higher quality materials. And they generally worked fine until somebody took a stone to them to "slick them up".

So, the short answer is no. Longer answer is generally, but many, many exceptions.

 

[dyl]

Scorch, thanks for the answer. So if I've got this right, here are the choices when a manufacturer - even modern day one, makes sears or a hammer or whatever it may be.

Start with stock already at a desired hardness and grind it down - but machining would be impractically rough on the tools. Cast / Forge / MIM a mild steel part and case harden. Cast/Forge/MIM a tougher/harder steel part and give a full heat treat (which would be pointless on really soft steel).

I'm disappointed that MIM is only surface hardened. In my mind I had thought case hardening was a thing of the past since a full heat treat would only be a couple steps more. Why not do it "right"? But I suppose you'd have to start out with tougher/harder steel instead of mild and the expense would be much greater just for the materials alone.

Well that might explain why the aftermarket sears /hammers that are made of tool steel are so darn expensive. Aside from lower production numbers, it's more expensive steel.

 

[dahermit]

Older Winchesters and Remingtons and Savages and H&Rs, etc, etc, were made of cast iron or mild steel and case hardened to give a longer-lasting wear surface...

Scorch, how does one surface harden a cast iron part?

 

[243winxb]

No, Get more opinions.

 

[dyl]

243winxb: ? I’d be happy to hear your opinion.

Dahermit: I assumed it was with things like “cherry red instant case harden” which is sold on Amazon, I might be tempted to try it some day.

 

[dahermit]

Dahermit: I assumed it was with things like “cherry red instant case harden” which is sold on Amazon, I might be tempted to try it some day.

The question was facetious in that Cast Iron is too high in carbon content to allow case hardening...it would harden all the way through when heated and quenched. Case Hardening requires a low carbon steel that is infused with carbon on its surface.

 

[dyl]

dahermit - Oh I get it. We've reached new depths, heat treat humor!

Is it possible to only case harden high carbon metal if you choose not to quench? If the case hardening compound is like a powder or granule, I didn't think the sudden drop in temperature from immersion in case hardening compound would be as dramatic as a liquid quenching agent. I thought the granules just melted onto the heated piece. And without a formal quench and temper, only the outside would have the hardness which comes from melted bits of whatever you've used as a case hardening compound. That's kind of what bothered me about the thought of case hardening something made of decent steel: you ruin whatever heat treat has been done by heating it to cherry red, and then after the case hardening compound has been melted onto it, only the outside is hard and the rest is soft. In that case it would be much better to do a formal heat treat because there would be so much more to be gained.

I could be wrong. Very wrong. Let me know if I am, I'm just exploring here.

 

[Hawg]

MIM parts don't need to be case hardened unless they weren't made correctly. They're already through hardened. In the old days gun parts including frames were made from case hardened wrought iron not cast iron.

 

[dahermit]

dahermit - Oh I get it. We've reached new depths, heat treat humor!

Is it possible to only case harden high carbon metal if you choose not to quench? If the case hardening compound is like a powder or granule, I didn't think the sudden drop in temperature from immersion in case hardening compound would be as dramatic as a liquid quenching agent. I thought the granules just melted onto the heated piece. And without a formal quench and temper, only the outside would have the hardness which comes from melted bits of whatever you've used as a case hardening compound. That's kind of what bothered me about the thought of case hardening something made of decent steel: you ruin whatever heat treat has been done by heating it to cherry red, and then after the case hardening compound has been melted onto it, only the outside is hard and the rest is soft. In that case it would be much better to do a formal heat treat because there would be so much more to be gained.

I could be wrong. Very wrong. Let me know if I am, I'm just exploring here.

Case hardening comes about when a carbonaceous (full of carbon) material is infused into the surface of a low carbon steel. What makes a steel harder is the Ferrite Changing to Austenite at Red heat and then changed to Martensite when it is quenched...no quench, no hardening. A low carbon steel does not have enough carbon in it to harden through (generally, unless using some sophisticated sub zero quench, etc.), so a thin layer of carbon is added by using a product containing carbon like "Casenite." In a case harden, only a thin outside layer of the steel hardens when it is taken to a Red heat and quenched. Cast Iron on the other hand actually has more carbon in it than high carbon steel. If it is heated to Red heat and quenched, it hardens all the way thorough.

I think the problem of understanding what cast iron is, is that its name belies the fact that it has more carbon than steels, not less as in pure elemental iron.