flat bending, any suggestions? *updated*

[Arisaka]

That's actually a badass jig. is throw a flat in there and do it man.

[Hoagiem]

Fastenal sells all thread in the higher grades, I forgot that the grade 5 and 8 have more shoulder than threads when they get a bit longer.

[shortround13]

update in first posting...if anybody is interested

[LessTalkMoreShoot]

Nice job, OP!

[nicoroshi]

looks like a nice jig, and appears to do a fine job bending flats.

[shortround13]

Ugh...so maybe it was dumb luck the first time....
Checking with calipers reveals that the rails on the first flat were pretty close, about 0.15 mm difference. Close enough for an ak.
But, 2 subsequent flats later, even after careful placement, one flat had one side 1mm higher....definitely visible. A second try and even more time spent lining it up and I still am about 0.4 mm higher on one side at the front. Weird thing is the back is almost dead even. So, is that unacceptable tolerance for an ak?
I'm about to the point of just buying the ak builder jig.....or can I make this work?

[meaty-btz]

Ugh...so maybe it was dumb luck the first time....
Checking with calipers reveals that the rails on the first flat were pretty close, about 0.15 mm difference. Close enough for an ak.
But, 2 subsequent flats later, even after careful placement, one flat had one side 1mm higher....definitely visible. A second try and even more time spent lining it up and I still am about 0.4 mm higher on one side at the front. Weird thing is the back is almost dead even. So, is that unacceptable tolerance for an ak?
I'm about to the point of just buying the ak builder jig.....or can I make this work?

AK builder flats? AK74?

[shortround13]

The flat that was 1mm off was a 74. The one off by .4mm was a 47. And yea...both ak builder flats.

[meaty-btz]

Yup, that is a known problem with AK builder 47 flats and 1mm is about normal for the deviation I have seen. It is nice to see your die causing the same deviation we are seeing with the AK-Builder Bending Die.

We should probably contact Kurtis about this. I have seen way too many being off. Something is wrong here and it isn't the die. It's the flats. If it was just me, cool. But tons of people are having this issue. I've had way too many that were off. I was able to correct them with work but, it isn't the same. Something is wrong with his flats

[shortround13]

What did you end up doing to fix the bent flat? Good to know I didn't royally screw up my jig....I put a lot of work into it lol and was kind of depressed

[meaty-btz]

I threw one out and the other was on the right side so all i did was flatten out the upper flange (for the front trunnion) and then rebent it. All with great care. Was it perfect? Hell no. Close enough, but very little "flange" was left for the front right side of the trunnion. Frankly the only solid fix is to manual tweak and measure the flat rather than going by the mag-well pins.

It is also my opinion that there are out of spec upper other parts on the flat as well. Everyone seems to be having the problem and the only way to get it square on is to mess with it while clamping into the die and adjusting it slowly till perfect then bending.

[shortround13]

Yea...that's what I was doing. Measuring each side with calipers until nearly perfect and tightening down the die and rechecking again before bending. But still something seems to be amiss.

I just sent an email to Curtis, wait and see what his reply is.

I have a question I was hoping you might be able to answer. I have a home made flat bending jig, comprised of a steel bottom plate, 2 angle iron side pieces spaced to give the correct dimensions of a bent receiver, and 2 flat bar stocks to sandwich the flat. the top piece (which ends up on the inside of the bent flat) has been milled to allow relief cuts for the mag well stabilizers and the flange at the top/front of the mag well to allow removal once bent. I have also made alignment holes in the mag well area, as well as the rear rivet hole for the trigger guard. I spent quite a bit of time with the calipers, making sure my flat was evenly aligned and centered, and with 3 attempts, I have one ak 47 flat that came out fine. one ak 74 flat that was 1mm higher at the front on the right side, although it was maybe only 0.1 mm difference at the rear. and one ak 47 flat that was 0.4mm higher on the left side at the front, and again very close at about only 0.1mm difference at the rear. I have also heard on various forums that other people have been experiencing similar problems, with various bending jigs ranging from home built to the ak builder jig. Is there another aspect that I am missing, that is causing the flat the become uncentered as the bending begins? Is it possible there is some deviation in the flat itself? Is there any way to correct this issue once the flat has been bent? I appreciate any information/advise you may have concerning this issue.

attached are some pictures to help. the pictures of the flats, one was bent using your jig at a build party, one was bent using mine, and I honestly can't remember which was which at this point.

[shortround13]

Hmmmm.....still no reply. Maybe he's busy. Maybe some of you who have also experienced some issues should email him too.

[meaty-btz]

i've done the email and gotten no reply either. He seems a stand up guy and he makes good product, except in this case... *shrug*

[Ryan in SD]

Flat bending 101:

The die in this case should be beefier despite being bolted down to a support plate. The 1/4" steel will flex near the top and flex less the closer to the plate it gets. BUT, the angle of the flat gets bent near the top, so the plate isnt helping you up there as much.

The punch and die need to be longer than the flat. You can see in the pic where the sharp bend abruptly stops where the flat overhangs the punch AND the die.

When measuring to make sure its centered, you need to hit two points farthest away from each other on each side.

IE. Measure Front right then back right. (should be the same.)

Then confirm number is close to front left then back left. (should be close to the numbers you were getting on the opposite side)

Otherwise, good work. Looks like your design has potential.

-edit
You might have better luck using 1/4 angle as the die if you flip it over and push from the more laterally supported side. Though having a base to push down on it may be hard to figure out.