Bending AK flats
- Thread starter kb0zos
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The biggest problem I see is people either not centering the flat, or not tightening the flat into the jig good enough, which causes the bottom of the flat to bow out a bit once bent, which also creates rounded bends, instead of nice sharp bends.
Use a mic to make sure the flat is centered on the jig front to rear, then tighten the hell out of it to the mandrel, then press slowly up and down the length of the receiver, and do not exceed the bend rate of the metal, and it should fold up nicely.
Use a mic to make sure the flat is centered on the jig front to rear, then tighten the hell out of it to the mandrel, then press slowly up and down the length of the receiver, and do not exceed the bend rate of the metal, and it should fold up nicely.
How much are people paying on average per flat? Even at the price I paid messing up 10 would get expensive.
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In all reality, bending the flat is the *easiest* part of making your own receiver.
You still have to weld in the rails and rivet the center support before it's *done*.
The best thing you can do if you can't find someone local, is to go on youtube, and look for videos of people using the same jig you've got. Watch them a few times, and you should have everything you need to know.
You still have to weld in the rails and rivet the center support before it's *done*.
The best thing you can do if you can't find someone local, is to go on youtube, and look for videos of people using the same jig you've got. Watch them a few times, and you should have everything you need to know.
A_Matthew
Member
Yeah, bending flats is pretty easy. I used a brake, made sure the lines I drew were in the right spot, and bent away. Came out pretty much perfect. The second one my friend and I did was a little bit to narrow, so we carefully pushed the sides out, and it is now where it should be.
Wish you well on your build.
Wish you well on your build.
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I believe that they were running about $40 or so at a gunshow several months ago.
AK-builder.com has them for 20-ish, with prices varying slightly depending on the make/model of the rifle.
Tapco has had them for as little as 10 bucks in the past, but comparing the AK-builder to Tapco flats is no comparison, and I will only build with AK-builder flats.
I would, however, recommend "practicing" on a tapco flat or two before moving up to the real thing, if I was concerned about messing it up...
Having worked on an Amada 100 ton press brake for two years, I can say you can't exercise to much OCD to get a flat perfectly positioned and precisely bent. Losing two or three out of 100 parts was dirt common, up to ten frequent. That was with CNC controlled programming, which still required almost artistic finesse to get small parts to within +/-.015", and large panels within 1/8" - typical for automotive.
The backstops can't vary, the dies can't wear, the temperature must be consistent, the pressure controlled to within pounds, and none of it is. There will be variations, that creates an acceptable tolerance issue. Two simple bends done within the same minute on the same die set with no movement of the backstop can be 10 degrees different - all because of the quality of the material. It's never completely homogeneous, can't be consistently annealed, gets workhardened differently bend to bend.
Expect it to be difficult, use every precaution you can, because a loss rate of even 5% in a sample of two becomes 50%. It's something that takes feel, and can't be done by the casual workman on the first attempt with high success, any more than you can grab a pinstriping brush and do Von Dutch professional graphics the first time. Grab every craft tip and bandaid process to assist that you can - it's just time lost if it didn't actually help, but it's a part lost if your skillset needed it.
One way to visually express it is that the part costs pennies, once formed and rejected at the next work station, it gets charged back in $10 increments. And there's no point in losing money on it, even if it is a hobby.
The backstops can't vary, the dies can't wear, the temperature must be consistent, the pressure controlled to within pounds, and none of it is. There will be variations, that creates an acceptable tolerance issue. Two simple bends done within the same minute on the same die set with no movement of the backstop can be 10 degrees different - all because of the quality of the material. It's never completely homogeneous, can't be consistently annealed, gets workhardened differently bend to bend.
Expect it to be difficult, use every precaution you can, because a loss rate of even 5% in a sample of two becomes 50%. It's something that takes feel, and can't be done by the casual workman on the first attempt with high success, any more than you can grab a pinstriping brush and do Von Dutch professional graphics the first time. Grab every craft tip and bandaid process to assist that you can - it's just time lost if it didn't actually help, but it's a part lost if your skillset needed it.
One way to visually express it is that the part costs pennies, once formed and rejected at the next work station, it gets charged back in $10 increments. And there's no point in losing money on it, even if it is a hobby.
Is heating til red and then quenching in water sufficient?
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briansmithwins
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Just to toss this out there: Nodak has bent, drilled, and welded AK receivers for $43.
http://www.nodakspud.com/page2.htm
BSW
http://www.nodakspud.com/page2.htm
BSW
Unless I missed something the receivers were 5.45. I do thank you for the suggestion though. I'm sure someone else here is probably looking for that setup.
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briansmithwins
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They had 7.62x39 receivers for $55.
The $43 ones had custom magwells and were a special order.
BSW
The $43 ones had custom magwells and were a special order.
BSW
"Is heating til red and then quenching in water sufficient?"
I Think a light oil is better.
The pin holes will start to stretch after 500-750 rounds if something isn't done. The trigger group gets loose, and after a while the sear won't catch so good anymore.
My "guess" on that flat. Romanian? Definitely for an underfolding stock.
I Think a light oil is better.
The pin holes will start to stretch after 500-750 rounds if something isn't done. The trigger group gets loose, and after a while the sear won't catch so good anymore.
My "guess" on that flat. Romanian? Definitely for an underfolding stock.
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A_Matthew
Member
kb0zos said:
I bought my kit from AK-Builders.com, and it had a US made barrel already headspaced and attached to the front trunnion. In that case, the only other things you need are a receiver, a US made trigger group and a US made muzzle attachment. (The trigger group and muzzle attachment are to maintain 922r compliance.)
If your kit does not have a US made barrel, then you'll need an extra part that that counts as a 922r compliant, such as a Tapco piston, or a stock, etc... But make sure it was made in the USA.
That flat is for a Yugoslavian M70AB2, which utilizes an underfolding rear stock.
To use that flat, you will need a yugoslavian kit with an underfolding stock. To use any other kit will require you to use at the very least, the yugoslavian front and rear trunnion.
You will need the flat, obviously, and the necessary parts to complete the flat, which consist of:
Lower bolt guide rails
Center Support Rivet
Center Support Bushing
The lower bolt guide rails will need to be welded in place once the flat is bent. A welder setup for sheet metal, or a spot welder is needed for this step.
The center support rivet and bushing act as a single unit, and provide some rigidity to the receiver,l once formed. The bushing will be located inside the receiver, and the rivet will pass through and be formed on the outside. A press and riveting tools are needed for this step.
There is also the potential that you will need to ream out the axis pin holes, depending on who made the flat. AK-builder flats need to be reamed using a 5mm and 7mm reamer in order for the axis pins to fit. Drill bits cannot be substituted here, unless you can find 5mm and 7mm drill bits, which I have never seen in the average big-box home & tool stores.
Heat-treating the receiver is the final step, and cannot be skipped, as the axis pin holes WILL deform over time. I use oxy-acet and quench in oil with a very high degree of success. Some people go a step further and heat-treat the entire receiver. I have never done this and have noticed no ill-effect. Factory AKs are generally fully heat-treated though...
To complete the rifle, you will need:
Complete rifle kit
Specific rivet set per rifle configuration
Necessary US-made parts for 922(r) compliance
Knowledge of the process to complete
If your kit comes with a US-made barrel that has not been headspaced, or with an original barrel from another kit, or is an otherwise "non-numbers-matching kit" you will need to set the headspacing on the rifle, which will require a set of headspacing gauges, as well as the knowledge on how to use them.
If this is the case, this opens the door to the potential need for a new, and possibly oversized barrel pin, and appropriate barrel pin reamer.
And of course, everything said is under the assumption that all other necessary tools to complete a receiver are present, such as all necessary riveting tools, press, etc.
Building your own from a flat can be fun and satisfying, but if you're only building one, it's nowhere near cost effective (unless you have access to a buddy with the tools). With what I've spent on tooling I could have purchased a few more guns. If I were only doing one, I'd strongly consider a Nodak receiver.
A_Matthew
Member
kb0zos said:
I've used a brake before to bend flats with, and it worked pretty well. Got it right first time. I don't know if it was a finger brake or not.
kimberkid
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I've built a couple on No-Dac Spud receivers, and bent a few Tapco flats to build on as well. It isn't rocket science ... they build these things in caves 
If you've got a complete numbers matching kit you don't need head spacing gauges.
The holes on the Tapco's are close but not quite right ... for instance the front 4 trigger guard holes are about 1/16" to 1/32" too close to the mag well and the holes in the rails are also off about the same, setting the lower rails a bit too low.
A buddy and I built own own jig with some 2" angle iron for the jig a piece of 1-1/8 square steel for the mandrel and a piece of 1 1/8 x 1/4 to secure the flat to the mandrel ... if you are using flats that have the top rail already bent you will have to do some grinding to the top of the mandrel as well as cut a relief for the magwell dimples.
We also made our own riveting tools and he has a welder ... we f-ed up a couple flats until we realized if we have locating holes it would keep the flat centered ... our first ones aren't pretty but they are functional.
Here's the 4 of mine all based on Hungarian AMD-65 kits, and Tapco compliance kits. The rifles all have Romanian barrels and gas-tubes but the pistol has the original barrel ... they have been parkerized but not painted yet, and not sure if I'm going to paint them or not. The underfolder is also a Romanian stock and was the first ... it also has the nastiest rivit heads
If you've got a complete numbers matching kit you don't need head spacing gauges. The holes on the Tapco's are close but not quite right ... for instance the front 4 trigger guard holes are about 1/16" to 1/32" too close to the mag well and the holes in the rails are also off about the same, setting the lower rails a bit too low.
A buddy and I built own own jig with some 2" angle iron for the jig a piece of 1-1/8 square steel for the mandrel and a piece of 1 1/8 x 1/4 to secure the flat to the mandrel ... if you are using flats that have the top rail already bent you will have to do some grinding to the top of the mandrel as well as cut a relief for the magwell dimples.
We also made our own riveting tools and he has a welder ... we f-ed up a couple flats until we realized if we have locating holes it would keep the flat centered ... our first ones aren't pretty but they are functional.
Here's the 4 of mine all based on Hungarian AMD-65 kits, and Tapco compliance kits. The rifles all have Romanian barrels and gas-tubes but the pistol has the original barrel ... they have been parkerized but not painted yet, and not sure if I'm going to paint them or not. The underfolder is also a Romanian stock and was the first ... it also has the nastiest rivit heads
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