Another out of spec AK-Builder flat

[meaty-btz]

Yup checked out my latest flat and the front flange that fits into the trunnion is actually .015 shorter on one side than the other. The upper rails are about .005 off from each other so it is inconsistent. trashed.

Will see how the others check out. That makes two out of about 6.

[CSACANNONEER]

AKs have a pretty wide gap of acceptable tolerances. 0.005" is well within original specs!

[TURBOELKY]

Sounds fine.

[meaty-btz]

The rest of the upper rails at .005 are fine. What bothers me is because one of the front flanges was shorter than the other the trunnion is not clocked level with the floor of the receiver. It is level with the upper rails but it pulled up on the short side when it was riveted. It will probably work but I will have to shave some wood to get everything to fit right. *shrug*

[SJgunguy24]

The rest of the upper rails at .005 are fine. What bothers me is because one of the front flanges was shorter than the other the trunnion is not clocked level with the floor of the receiver. It is level with the upper rails but it pulled up on the short side when it was riveted. It will probably work but I will have to shave some wood to get everything to fit right. *shrug*

Hammer to fit, paint to match. Sound good to me.

[meaty-btz]

Hammer to fit, paint to match. Sound good to me.

I'd actually need to stretch the metal on one side, thankfully it seems with further measuring that the rest of the flat is in spec and level.. so it's just a cosmetic on the front and maybe some wood cutting to make it all fit.

Since the pulled up side levels off it would just seem the flange was just indeed cut incorrectly and the rest of the flat was in spec... or close enough. Anyways if it screws up things too badly I guess I can cut it apart pretty easily.

[mr.]

Are you sure it wasn't off when you bent it? I noticed some times the mag well is alittle bigger than others and I have to center the flat on the jig rather than rely on the dowel pins. I'm talking .01-.02 of wiggle between the mag well and dowel pins.

-joe

[mr.]

Also is this a flat with pre drilled rivet holes?

[kcstott]

I've noticed it to but only on 74 flats. The 47 flat that I've seen are good.
I corrected the bend by dropping the alignment pins. Aligning it by hand and then bent the flat.

[SJgunguy24]

I'd actually need to stretch the metal on one side, thankfully it seems with further measuring that the rest of the flat is in spec and level.. so it's just a cosmetic on the front and maybe some wood cutting to make it all fit.

Since the pulled up side levels off it would just seem the flange was just indeed cut incorrectly and the rest of the flat was in spec... or close enough. Anyways if it screws up things too badly I guess I can cut it apart pretty easily.

Snips are a wonderful invention. I'm still using my old style jig, I had to mill the top part to get the prebent rails to fit. I actually have a couple of the old flats and my top rail jig.
It kills me that my old jig was 300$ and the new better jig is half that price.

[mr.]

Snips are a wonderful invention. I'm still using my old style jig, I had to mill the top part to get the prebent rails to fit. I actually have a couple of the old flats and my top rail jig.
It kills me that my old jig was 300$ and the new better jig is half that price.


I have a few old flats but no upper rail bender =(

[meaty-btz]

well no predrilled trunnion holes. Next time I will verify sizing to ensure that there is no offset that might result in the same issue. I don't know if this is correctable or not. Rebend?

You guys are a wealth of info. I was kinda steamed to have two off bends.

[mr.]

Id just put it together, it's called character =p

[mr.]

Btw let's see a pic.

[kcstott]

well no predrilled trunnion holes. Next time I will verify sizing to ensure that there is no offset that might result in the same issue. I don't know if this is correctable or not. Rebend?

You guys are a wealth of info. I was kinda steamed to have two off bends.

Yeah it's fixable..... chuck it and start over

[SJgunguy24]

well no predrilled trunnion holes. Next time I will verify sizing to ensure that there is no offset that might result in the same issue. I don't know if this is correctable or not. Rebend?

You guys are a wealth of info. I was kinda steamed to have two off bends.

Yeah it's fixable..... chuck it and start over

I'd have to agree with KC, if you try to brake the metal over again, it's only going to weaken it at the brake line and when you try to force the stock in there it'll shear at that line. When you brake it, your actually changing the grain structure of the metal. Not something you want to keep doing to the same piece of material.

[kcstott]

I'd have to agree with KC, if you try to brake the metal over again, it's only going to weaken it at the brake line and when you try to force the stock in there it'll shear at that line. When you brake it, your actually changing the grain structure of the metal. Not something you want to keep doing to the same piece of material.

That and the metal shrunk once already bending if flat and trying to rebend it will not put it back.

either build it out of kilter or chuck it and start over. Flats are cheep

Now to be clear on bending a new flat. I had to drop my alignment pins. I believe the mag well is slightly off center and that caused the issue. It was only .020" or so. I dropped the pins, clamped it down gently then used a set of calipers to get it centered and straight. ROYAL PAIN IN THE ARSE to do. But if you are careful, get it aligned correctly, tighten it up, measure again before bending. it will work. I got the sides within .005" of each other and straitness within .002" Read that as WITHIN not plus or minus

[meaty-btz]

That and the metal shrunk once already bending if flat and trying to rebend it will not put it back.

either build it out of kilter or chuck it and start over. Flats are cheep

Now to be clear on bending a new flat. I had to drop my alignment pins. I believe the mag well is slightly off center and that caused the issue. It was only .020" or so. I dropped the pins, clamped it down gently then used a set of calipers to get it centered and straight. ROYAL PAIN IN THE ARSE to do. But if you are careful, get it aligned correctly, tighten it up, measure again before bending. it will work. I got the sides within .005" of each other and straitness within .002" Read that as WITHIN not plus or minus

Nice, I took your comment about the magwell and measured. Yup. It was off. I'll be, so it wasn't the cut for the trunnion flange but the magwell that caused the flat to be off center in the die. As you guess this one is also a 74 flat. Why is it appearing in the 74 flats?

[SJgunguy24]

Nice, I took your comment about the magwell and measured. Yup. It was off. I'll be, so it wasn't the cut for the trunnion flange but the magwell that caused the flat to be off center in the die. As you guess this one is also a 74 flat. Why is it appearing in the 74 flats?

Maybe it's a good idea to drill alighnment holes and add pins to the new jigs like the old style. That way your coming off the true centerline and your receiver will be straight regardless. You can always trim a mag well and use the lower rails to keep the mag centered.

[kcstott]

Nice, I took your comment about the magwell and measured. Yup. It was off. I'll be, so it wasn't the cut for the trunnion flange but the magwell that caused the flat to be off center in the die. As you guess this one is also a 74 flat. Why is it appearing in the 74 flats?

No idea. I don't build to many 74's so I don't see to many flats That hand full i've seen are off center.

[meaty-btz]

Ok, got in the new flat. Checked it. All within .004. I bolt it into the bending die. Check everything. Yup looks good. Bend... Song of a.. its off again, but only in the front. Checked mag well, still centered and in spec. A couple of things I noticed. The upper rail flange on the left side of the receiver is smaller than the right. Well that is damned peculiar. Anyways since then I checked all the way back on the bent receiver and it is square and in spec all the way back. So I took my body hammers and reworked the front left rail.. flattened and stretched it a bit. Now I am in spec but I have almost no crease on the left side at the trunnion. I didn't touch the rails anywhere where the carrier will ride. So I plan to get better metal stretch and control by riveting it in place on the front trunnion and then using a tool of some fashion drive (stretching) the metal into the groove in the front trunnion for more strength.

My jig could be messed up but if everything checks within .005 and then you bend and end up with .012-.02 out on one side. Dunno. I do note that the radius of the bend on the "long" side is sharper than on the "short" side. Both side drop with a bang when folding so.. Might be something there.

Anyways, yes there is a slight ripple in that upper flange for the left side trunnion. I just straightened out the front a little bit extra to see about length. As it turns out that little bent part is just right now. Both sides are 1.289 and 1.288 Close enough for me. Turns out it is hard to take a picture with a cell cam and hold the part at the same time.. so sorry it isn't a square shot.

[baih777]

what jig are you using ?

[meaty-btz]

the newer AK-builder one.