How do I heat treat an AK receiver?

[kymasabe]

If I buy a flat receiver and bend it myself, how do I heat treat it? I guess I could look in the phone book for a someone semi-locally who does that sort of thing but is it possible to heat treat it myself?

[hoytinak]

The ejector on the left lower rail also needs to be hardened. Since most finishes that you will apply to the completed firearm will require that it be baked at 400 degrees or more we will only concern ourselves with spot heat treating the FCG holes and the ejector. The hammer and trigger pin holes on both sides of the receiver need to be hardened due to the amount of stress they receive during the life of the rifle.

You will need the following:
MAPP gas torch
Sand paper
Pliers
Pail of water
Work Gloves

There are two steps to heat treating metal for an AK receiver. The first is to harden it by taking it up to 1500 degrees F and then quenching it. This will make it very hard but also very brittle. The second step is to temper it by taking the metal up to 800 degrees F and letting it air cool. MAPP gas will heat the metal to the proper temperatures in a reasonable span of time. The way to gauge the temperature of the metal is by color. When the metal gets to a bright glowing orange/yellow it is time to quench it in the pail of water. Sand the treated area to bare metal and reheat it until it is a gray/blue. At this point set it aside to air cool. Do the ejector (Left lower rail) first to get a feel for the process.

You will also need to heat treat the hammer and trigger holes (FCG). These are the pivot pin holes located on both sides of the receiver. Heat and quench each hole and then temper them individually and let them air cool.

[dipper]

Being a tool maker, I have heat treated countless pieces of steel in all types, grades, and configuration---for many different applications.
I would not heat treat a receiver for any firearm as hoytinak describes unless I lived in a third world country with no access to proper methods and my life depended on me having anything that would fire a few rounds.
Heat treating is a very critical process often overlooked by people who do not know what they are doing or have little knowledge about the subject.
Harding temp. and annealing temp depend on what steel you are using and some steels require fairly strict adherence to temperatures and times.
I am sure that in some places in this world, someone has built AK's as described by hoytinak but it is not necessary here in the US---there are MANY heat treating business's out there that can do it properly and for minimal costs.
Keep in mind that any part of a firearm that is to soft or to hard can be a big problem.
Also, keep in mind that you never know on which round something could let go---could be on the 5th or 500th round---no way to tell.

[kymasabe]

Someone told me today to heat the receiver to cherry red and quench it in a bucket of water. Would make it hard but brittle. Next step was to immerse it in a metal tray full of brake fluid, put the tray in my grill, light the brake fluid, and let it burn until the brake fluid is consumed, was told it would take 1/2 hour or so and the receiver would be good to go after cleaning and painting/finishing. Sounds a little too easy to me.

[hoytinak]

I am sure that in some places in this world, someone has built AK's as described by hoytinak but it is not necessary here in the US

Myself and several buddies have built around 50 AKs total over the past 10 years using this method and we've never had any problems with it....and yes, we're all in the US.

[dipper]

Good for you hoytinak---not trying to be a jerk but it IS NOT the proper way to heat treat a receiver.
Glad to hear you and your friends haven't had any problems----YET!!
If you are making them for sale, or have sold any----assuming you have a manufactures license---I hope you have your liability insurance paid up---you may need it.
You are permitted to manufacture a rifle for your own personnel use without a manufacturers license---ya' all must have a pile of AK's!!---but I don't think you can transfer ownership or sell one without a license.
Also, if you shoot on any public ranges and something happens to the guy next to you you're in a world of hurt.

[kraigwy]

I think this comes under the heading of:

DONT TRY THIS AT HOME

[Swampghost]

I spent many years as a machinist. The co. that I worked for contracted with many aerospace and defense suppliers. Heat treating is NOT a DIY project when it comes to something that could literally 'blow up in your face', it's a job for pro's. They will do a Rockwell test and provide you with certification to CYA. Bear in mind that YOU are now becoming a 'manufacturer' and will be responsible for any problems that occur down the line.

Say that you decide to sell the piece or falls into someones elses hands by whatever means and some handloader overstuffs it, it blows fragments back and the new owner is blinded or worse, YOU will be held responsible. Telling a court of law that you heat treated the part according to some BS that you got off of the web will not fly very far.

I'm with dipper ATW and it really doesn't cost much to have it done professionally.

[hoytinak]

I didn't say it was the best (of course it's better to have it done by a pro) but it's a way to do it yourself (as the OP asked for).

[Jimro]

The mild steel that most people use for AK receivers is pretty damn hard to screw up. As far as heat treating by color, it isn't as sexy as a digitally controlled kiln, but it works.

Catastrophic failure is just as likely to come from impurities in the metal blank put there long before anyone ever decided to turn it into a receiver.

If you want to Cover Your A$$ then building an AK is probably not for you.

And as far as tempering steel with an open flame, that's how Colt finishes the barrels for M4 carbines. It's old as dirt tech, but it works.

Jimro

[TheManHimself]

What I've learned from The Firing Line today:

One of the advantages of the AK is that it can be cheaply manufactured with 19th-century metalworking technology by smelly bearded men in third world countries and still works forever without failing; however, if this method of construction is attempted by American citizens the rifle is extremely dangerous and prone to explode at any minute.

[dipper]

Can't agree with ANYTHING you said Jimro.
In over 30 years of tool making, I have seen guys screw up the most simple of tasks and I have worked with hundreds of people in the machining industry at all levels of experience.

"Catastrophic failure is just as likely to come from impurities in the metal blank put there long before anyone ever decided to turn it into a receiver."

Total BS

"If you want to Cover Your A$$ then building an AK is probably not for you"

More BS
If your saying that encouraging someone WITH NO EXPERIENCE to do the job right makes building an AK " not for you", well......
I didn't see the mention of a Rockwell Hardness tester anywhere in the "how to" description either----which beats the hell out of " hit it with a file".


"And as far as tempering steel with an open flame, that's how Colt finishes the barrels for M4 carbines. It's old as dirt tech, but it works."

What does that mean??
Many companies use that technique for annealing parts so what??
You can bet your butt that it is a very well controlled process with the temperature, time, and atmosphere tightly controlled-- it ain't like some guy out in the garage with a blow torch.
AND I'll bet that every so many parts are hardness checked and certified.

If you think telling someone with no experience to grab a torch and have at it is a good idea, well.......

Rifle receivers ain't washers or spacers---they are something that can hurt you---and INNOCENT people around you.
I just can't sit back and let someone tell someone else to do something like that---especially someone with no experience.

[dipper]

What I've learned from The Firing Line today:

One of the advantages of the AK is that it can be cheaply manufactured with 19th-century metalworking technology by smelly bearded men in third world countries and still works forever without failing; however, if this method of construction is attempted by American citizens the rifle is extremely dangerous and prone to explode at any minute.



Then you need to re-read what has been written and try to comprehend what was said better!!

[hoytinak]

One of the advantages of the AK is that it can be cheaply manufactured with 19th-century metalworking technology by smelly bearded men in third world countries and still works forever without failing; however, if this method of construction is attempted by American citizens the rifle is extremely dangerous and prone to explode at any minute.

Kinda funny, that's what I was thinking myself.

[Swampghost]

I know, we used to oil and water treat as well as anneal our own parts but they weren't as critical as parts for a firearm.
We machined the actions for the 30 mm GAU-8 used in the A-10's and the M 134 Miniguns. They went out for heat treating and final grinding.

[DnPRK]

dipper, I take it that you have no familiarity with AKs or else you wouldn't post what you have posted.

An AK is not a Remchester. The trunnion of a AK is a machined and classically heat treated part that serves the same function as the receiver ring and lug bearing surfaces of your Remchester. In other words, the trunnion takes the stresses and has to be heat treated for strength. The trunnion is riveted into a thin, mild steel, formed sheet metal receiver. The AK receiver is not a load bearing, stressed part. Spot hardening of the sheet steel receiver is needed at the locations posted by hoytinak to prevent peening of the fixed ejector and elongation of the hammer and trigger pin holes.

When the Soviets first started making AKs, they tried heat treating the stamped receivers like you would a Remchester and had many failures. The thin receivers would warp to the point of being useless or crack from being too brittle. They reverted to use of machined receivers until they got the spot heat treatment scheme worked out.

BTW, spot heat treating is not foreign to US manufactured firearms either. One example of spot hardening is the slide of the 1911A1. An example of spot annealing is the heel of the M1 Garand.

[Swampghost]

Pie fight here!

[BeCoole]

The only reason you heat treat an AK receiver is for wear resistance.
As pointed out above, it does not bear any load.

You heat treat the ejector so that it doesn't get peened by the ejecting steel cases.

No need for rocket science with this.

[dipper]

DnPRK---Your right, I have limited ( some) experience with AK's BUT, Your wrong---EVERYTHING I posted still applies and I think you are missing my point/points entirely.
I have made a "few" firearms related parts however and have talked with a few firearms designers and engineers.
First, I have been told by these engineers and designers that NO PART used on any firearm can be out of spec for hardness that's NO PART.
It doesn't matter if it is in your words "The AK receiver is not a load bearing, stressed part."
It STILL has to fall within specs for hardness----JUST LIKE a set of rings and bases do on a bolt rifle or a lever on a lever action etc. etc.---they are not a "stressed" part, but they CANNOT be out of spec for hardness---like 58-60 Rc.
That would be to hard and NO part on a firearm can be out of spec and be to hard------NO Part.

SO, again, here is a guy ( the OP ) with no experience, no rockwell tester and are we suppose to say " grab a torch" ??

Do you think AKs are spot hardened with a torch??

Let me ask you this, can you reliably "spot harden" a hole with a torch??
I mean a hand held every day common in your garage set-up??

"
When the Soviets first started making AKs, they tried heat treating the stamped receivers like you would a Remchester and had many failures. The thin receivers would warp to the point of being useless or crack from being too brittle. They reverted to use of machined receivers until they got the spot heat treatment scheme worked out."


Yep, but we don't have that trouble today, we can heat treat some very thin parts with very little warping.
And the machined receivers were/are machined out of pre-hard.

"
BTW, spot heat treating is not foreign to US manufactured firearms either. One example of spot hardening is the slide of the 1911A1. An example of spot annealing is the heel of the M1 Garand."

No Kidding!!
Why I never did knew/did that before!!
Thanks for the heads up!!

Point is, AGAIN, if you or anyone else thinks it's a good idea for someone with no experience and that doesn't have what he needs to check the hardness to wing it ---that's up to you.

My arguement is NOT how a AK receiver is made or what the factories do---it's suggesting that a rookie can accomplish safe specs with his torch---I say there is a GOOD chance he can't---and I will not recommend it.

Nuff said on this!!

[BeCoole]

Tempsticks

[Jimro]

Dipper,

If you don't agree with anything I say I guess I need to go cry in a corner or something.

I shoot two AK's with home bent receivers. I give you permission to gloat when one of them blows up and kills me.

Jimro

[1SGT Harlin]

Listen U jabroniiies,
The AK was designed to be built my 3rd world pheasants. As I live near Detriot I know was the 3rd world looks like. As yes, you can heat treat an AK at home. I would use temple sticks to control the temp but, yes a regular MAPP would work fine. I'd quench it in used motor oil myself

[Swampghost]

1SGT, you DO realize that your statement opens you to litigation if something blows up? Yep, it's the web and you may feel somewhat insulated but even a dummy like me can get your IP. Lawyers can do better.

[Bill DeShivs]

I hand make a lot of springs, and I do it with a torch. I'm pretty damned good at it-no failures in about a thousand springs. Here is something you don't realize- you can not "spot harden" anything. For carbon steel to be hardened, it must be heated to the proper temperature and quenched, so you would have to harden the entire receiver, then temper it back-or it will be very brittle. You can't do this in "spots."

[dipper]

+1 Bill