Heat treating

[gsrcrxsi]

So it seems most people just spot treat the holes? Is this correct? Why doesn't anyone have the entire bent flat treated before drilling holes or welding the rails? And then drill the holes.

Thoughts?

Secondary question. Does anyone have the ability to heat treat an entire completed receiver? To "supervise" me doing it myself of course.

 

[armed ferret]

You wanna drill hardened steel, be my guest. I get the pre-drilled NDS receivers whenever possible.

Axis pin holes are really the only ones that need heat treating if you're bending your own flat. Attempting to heat treat a complete receiver without A LOT of money/time invested in proper kiln and jigs will only result in lots of warped receivers.

 

[hvymax]

A few seconds with an oxy-acetylene torch and a water quench is all it takes to heat treat each hole. Once carbon steel is heat treated anything that induces "state changing" temperatures such as welding will compromise the entire structure. Heat treating and tempering are a science all their own so KISS is your best bet. If you were to simply heat treat an entire reciever it would most likely be brittle and break. Carbon steel when heated to that bright "cherry red" and quenching it leaves it in a state much like glass so limiting it to localized areas leaves it supported so it can take wear without breaking.

 

[gsrcrxsi]

i have a henderson 80% receiver. pre-bent, rails already welded. jst have to drill holes and cut outs.

i know the NDS receiver is an option, but personally i wanted something not requiring an FFL or the associated wait/paperwork.

 

[Fox123]

Dont forget to treat the ejector as well.

 

[rob-cubed]

The ejector, and to a lesser extent the axis pin holes, are the only parts of the receiver with significant stresses that would slowly peen the metal. Thus the need for spot treating.

I have not attempted to heat treat my own receivers as a whole. While it's much more desirable IMO, once the rails are welded and it's riveted to the trunnion, the receiver will be plenty stiff enough to hold up to everything but real abuse.

Read up on the process of heat treating... it's easy, but also easy to screw up. Getting even, consistent temps and fast quenching are important to reach the right RH without stress fractures or having the final product be too hard/soft. You'd need jigs and a kiln to do the whole receiver at once and for that amount of hassle it's easier to get a commercial receiver.

 

[awptickes]

I don't blame you for not wanting to go with a pre-built receiver. It's a lot more expensive.

Used motor oil works better for the heat treating, higher thermal transfer coefficient, and you will case-harden at the same time. You want to spot-treat the axis holes to minimize the receiver warpage. You'll need oxy-acetaline to get it hot enough, MAPP gas may work if you have high-oxygen ambient air in your shop, propane will absolutely not get hot enough. Drill all holes smaller than needed before you spot harden, then ream out to proper size.

If you heat treat the whole receiver with flame, you will warp the metal. To heat treat the whole receiver, you need an oven designed to heat treat it.

Do some reading on some of the AK forums to get an idea of how you want to proceed.

Here's a few links to read:
http://archery.ar15.com/archive/topic.html?b=4&f=64&t=95521
http://pookieweb.dyndns.org:61129/ak/docs/construction/heattreat.htm
http://www.akfiles.com/forums/showthread.php?t=14475
http://www.longislandfirearms.com/forum/m-1344743933/s-all/ << this one is directly applicable to you.

 

[armed ferret]

I don't blame you for not wanting to go with a pre-built receiver. It's a lot more expensive.

AK-builder basic 7.62 flat: $20 (each)
AK-builder flat-bending jig: $170
Rail spot welder at HF: $150
Modified welding tong: $37.50

NDS-1 EZ: $85


In tooling alone, you've already bought more than 4 receivers. You'd need to bend 6 before you break even on tooling (not including cost of flats), and 7 before it becomes "cheaper" to bend. Even then, NDS is already 100% heat treated, stepped rails, and has factory-level bend quality. A receiver made from a flat will not be fully heat treated, nor will it have anywhere close to the quality of bending. (yes, i'm aware you can sell tooling off after you're done to the next builder and recoup some of the loss, but no real gun nut would ever do that, because who knows when I might build another one honey? )

Not to mention the extra several hours involved. And the price of the flats goes up pretty quickly as you change caliber, rifle type, etc. Granted, NDS receivers can do the same, but not as quickly, and not by as great a percentage of the original baseline.

In the end it's totally up to you. I have several rifles built off bent flats, and they look and work great. They were built before NDS was around though, and the only other options were Hesse/Vulcan (don't even go there, we all know the stories, keep it outta here) and Tapco flats...then Curtis (AK-Builder) came along. That was, what, 2004, 2005? Somewhere in there. The days of $89 Romanian kits.

Regardless, all recent builds i've participated in have been on NDS receivers, and will continue to be. The extra sixty bucks per is totally worth the time I don't have to spend possibly screwing up a $30 receiver flat, and still not have a fully heat treated receiver at the end of the day.

 

[awptickes]

You're forgetting transfer fees, which for some reason seem to keep going up everywhere.

 

[DarthZed]

The extra sixty bucks per is totally worth the time I don't have to spend possibly screwing up a $30 receiver flat, and still not have a fully heat treated receiver at the end of the day.

As Armed Ferret said, your time is worth money too. You need to factor that in as well. I understand wanting to build your own just to do it once, but from a price/quality standpoint; you aren't going to beat a NDS. We won't even talk about resale value should you need to sell it.

 

[armed ferret]

You're forgetting transfer fees, which for some reason seem to keep going up everywhere.

Call around, talk to IP's. If you know you're going to be building 3 AK's, save up, get all the receivers at once (which begets a quantity discount from NDS), and you should be able to find an FFL that won't charge you three transfer fees for one single order.

If they do, find another dealer. I've had a great experience with Dan at The Gun Connection. He's a bit outspoken, but I damn sure can't begrudge a man for speaking his mind in his own shop.

I also dealt with 2A sales when I won that turkey shotgun at the last big MDShooters event, and had a great experience with them as well.