View Full Version : Hardness/heat treating information
May 25, 2008, 08:28 PM
Can anyone tell me what parts are hardened in a 1911, an AK47, and a Ruger 10/22?
I know that most internals would be case hardened but I'm havng trouble finding specific information. Any ratings on the Rockwell C scale would be great.
May 25, 2008, 10:10 PM
No access to a hardness tester, but I can tell you parts of the 10/22 that are hardened. The bolt is hardened, the hammer is hardened, the sear is hardened, the disconnector is hardened as well as the firing pin. The V-block is also hardened. Now some of those thicker parts, like the bolt, may be case hardened. I know this because I have tried to drill and tap them. You either need really good sharp carbide tools or you need to anneal, then drill/tap, then reharden. This worked for my trigger group parts when I wanted to put in set screws for engagement adjsutment. I didn't mess with the hardness of the bolt though, I just bought a good carbide bit to get through that baby. As far as the AK, I haven't really putzed with it at all, but I would imagine that the same parts would be hardened or case hardened. Pretty much anything that will take a significant load, or impact, or hold some type of engagement will be hardened in some way. I don't know anything about the 1911, can't help there.
May 27, 2008, 01:48 PM
As has already been adequately stated most all steel, and sometimes special alloy parts are 'heat treated."
Steel must have enough 'points" of carbon to heat-treat.
For instance stees are classified by AISI or SAE numbers. From Ackley we learn that 4140 is an alloy steel; has chromium and molebdenum and has 40 "points" of carbon in it (or .4 of 1%).
In the heat-treat oven you will find what the decalescence point of that particular steel is. As you increase heat the pyrometer will increase to a point where the needle stops but heat is still being added and the steel becomes "non-magnetic." This is the decalescence point and for hardening this is when you remove the item and quench: in the proper quenching bath.
This is usually a F. temperature of around 1300 to 1500 degrees F.
Now, as the furnace is turned off, as the pyrometer needle comes down you will see a "stop" in the needle again as it gives off heat used to change the structure of the carbon and this is called the recalescense point.
Now, after the steel is "hardened" it must be drawn to around 500 to 700 degrees to "temper" or, to remove some of the "hardness" it has - springs are usually drawn to 650 to 700 degrees F. Other parts will only be drawn to 400 to 500 degrees F.
So, yes, all gun parts are heat-treated (or come heat-treated) from the supplier to a specified hardness or "temper." Tempering is simply removing some of the hardness already there from hardening!
The decalescence is so low in some steels that it will "work harden" under a drill or lathe or milling cutter!
Heat-treating is a very controlled process and alloying and heat-treating gives us our steels of today. In WWII subs were only good for 500 to 700 feet. Today, our alloy steel nuclear subs are good for over 3 times that depth and are welded in canvas shelters to keep them at a uniform temperature - very important!
Rifle actions, even years ago, were designed to not burst or rupture at over TWICE the pressure the brass case could withstand! The case is the weak link!
May 30, 2008, 11:24 AM
May 30, 2008, 11:48 AM
I would think that most modern guns use the steel as-is. Small parts such as sears, hammers and trigger assemblies are heat treated-as may be some barrels.
After engraving a lot of guns, I found that few were actually hardened. A Colt Woodsman comes to mind that had a slide so hard that my gravers broke points every 1/2 inch.
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