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I'm using Tapco flat blank and rails .According to Machinerey's Handbook I should heat in an oven to 1650 .Quench in water or oil . What temp should I draw to ? Should I draw it down at all?
Thanks
Jim
 

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water can cool it too fast and make the 4130 brittle, harder is not always better, motor oil will not make the metal too hard/brittle due to slower cooling.
 

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Happy Camper
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Cephus if it gets too brittle, the receiver could begin to crack over time. Just the opposite w/o treating - the holes will begin to egg-shape over time due to repeated stresses.

We have yet to see/hear any reports of an untreated receiver w/ egg-shaped holes. Would be nice (and expensive) to measure the holes, load up a few cases at the range, and then measure again. That would give us a baseline on how long the holes would be expected to last w/o heat treating.
 

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cosmonaut said:
Is there any particular type of oil that should be used?
At the BuildFest we had at _Disconnector_'s house a little while back, we used
a synthetic oil. He said that with the synthetic, it took a lot more heat to ignite
it, versus the standard oil.

With the # of rails that the guys (we had one guy doing the heating at one time,
so I KNOW that the oil's temp was cranked up), it did smoke some, but never
ignited.

Something to think about...:)
 

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Steelcore1964 said:
water can cool it too fast and make the 4130 brittle, harder is not always better, motor oil will not make the metal too hard/brittle due to slower cooling.
Steel core is right. It also causes much higher stresses in the steel due to the speed of cooling and you will get stress cracking. There are steels(1040- 1050) that need to be water quenched but this is not one of them. In fact you should probably heat your oil to at least room temperature if it has been outside or out in the garage in the winter. And one way to keep flame ups to a minimum is to submerge the whole piece so nothing is out in the air like a wick.
 

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hcpookie said:
We have yet to see/hear any reports of an untreated receiver w/ egg-shaped holes. Would be nice (and expensive) to measure the holes, load up a few cases at the range, and then measure again. That would give us a baseline on how long the holes would be expected to last w/o heat treating.
I had the holes on my first build (AMD-63) begin to eggshape and I didn't even fire it. Just the consant working of the hammer and trigger started the process (didn't heat treat the holes). I didn't measure the holes to start with and didn't measure them afterwards but I knew that the axis pins were snug in the begining. I then tried the heat an quench (in both oil and water) and I continued to see the holes open up. I then used Kasenit, heating the holes to red pouring the Kasenit on the holes (had a steel backup plate) and then reheated the holes to red again. I then quenched the receiver in clean water (as per directions). From that time on the holes have stayed the same. I don't know how brittle the receiver is around the holes but I do know that holes arn't egging anymore.

So having failed the standard oil-water quench method (at least for me) I use Kasenit for the critical holes.

On another but the same note, when I use Kasenit on my ejector it does become brittle that if you try to bend the ejector by hitting it it will break. If I would have to cut the ejector for some reason (after hardening it) I would use a carbide rotory file.

So in a nutshell, rather than worrying if I hardened the holes and ejector correctly using the quench method, I use Kasenit. The holes and ejector might be to hard or brittle but at least they won't wear and I don't beleive that the receiver will crack from the hammer/trigger action. This is my experiance and maybe someone else will reflect their's using Kasenit.
 

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What I have been doing is heating the holes & ejector to cherry red/orange and water quench. Then I polish to bare metal and reheat to blue black and let air cool. So far everything is looking good with no cracks or egging. I forgot where I read about this method but it seems to work. The ejector is hard but not brittle and shows no sign of wear after around 500 rounds and no fires....
 

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I actually found a web page from a steel company at one time that stated that 4130 steel should be water quenched instead of oil. I think the problem some people are having is that after heating to 1600 deg. and then quenching, you must temper the steel by reheating to around 750 deg. to bring the Rockwell hardness back down to around 35 or so.

Of course, the way everyone is heat treating using torches in the shop is not very accurate and I doubt if the results are going to be as good as a receiver properly treated completely like the ones from Global. That is just part of the fun of doing it yourself. If it fails down the road, make sure you have stocked up on flats and try again!
 

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I thought I read a while back that it should be heated until red and then quenched in oil, then re-heated and quenched in water. Are both steps necessary? Do you think the oil and quench would be good enough?
 

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Heat Treating and the finish of your AK

I am not an engineer but based on experience and may years of automotive work (body and paint and Mechanical) I would be concerned about finish problems using oil.

I have read the heat treating using map gas and getting the metal around the holes red then using water to quelch. Then reheat the holes to an even blue (less heat than before) and let them air cool. It has worked for me so far.

I would be concerned about oil being used to cool the metal causing problems with paint or finish bonding with the metal around the heat treated areas. Just a little oil can ruin a finish on an automobile when you paint one and if the oil is baked into the metal I can imagine the finish lifting.

Any one had that problem or am I just seeing Murphy at every turn. He usually turns up but I always overcome.
 

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Heat treat

I am new to this forum. Lots of great info
I build induction heat treating equipment. I asked one of our engineers about heat treating 4130. He said if you quench it in "20% Ucon A" it is not neccasary to temper it. Ucon is a common quenchant used in heat treat shops. I also used warm water to cut it down.
I just finished my AMD so do not have any test results yet. Hope to get to the range this weekend... Weather permitting
 

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Keep us posted on the condition after test firing. I have been using the oil to cool it. That does make sense it affecting the paint afterwards though. Now Im curious.
 

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I got to tell you guys that I've learned more in one week on this forum that in two years at another board I just don't want to mention.

Thanks.
 

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I'm getting ready to bend a couple flats and this thread has surely helped me out. Thank's to all who have posted!
Oh, Welcome Molson and thebigca! :welcome:
 
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