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Modified a Tapco flat to work with a Polish Underfolder

1452 Views 23 Replies 11 Participants Last post by  Tanker06
I wanted to take a break from building jigs and decided to use my milling machine for something different.

First thing was to fill in the rear trunion hole and grind them down. Then the fun part began... I didn't take any pictures, but the biggest part was getting the dimensions right considering that I was working with a flat not a bent receiver. The angles play a big part on where the holes line up.

Anyway.. here are a couple of pictures of before bending and after bending with my jig. The rivets are just stuck in to line everything up for now. I'm toying with the idea of modifying a bunch of flats and not drilling the trunion holes. Would anybody be interested in that?


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The only reason not to put the trunion holes is when the flat is bent they could possibly not line up if the bend isn't just right. I have 100 flats here from Tapco, but I don't want to bend too many just trying to figure out if it's perfect.

The dimensions were taken from a trunion and what was left of the sheet metal receiver. I put the trunion in my mill vise and used the digital readout to map out the dimensions to each hole from a specified point. Then I took an existing cad file that shows the whole flat and drew the holes in. The only problem was that the angle wasn't there for the holes so after printing out a bunch of transparant sheets to match up until I finally got close enough to make one flat. I need to tweak the four folder catch holes, but other than that it fit just fine.

It would be nice if there was somebody in the Kansas City area that needed one or two of these made up so I could practice without making more receivers than I will ever need for myself. Right now there are three or four receivers sitting on my bench that I probably won't use that are all bent up and ready.

When I took the underfolder apart I took pictures of each step so it would make a good guide on how to do it. When and if I get some time I'll make it up and post it on my website.
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If I get enough people that would actually want one I would waste a couple to try and make them as exact as I can. Otherwise I won't bother with buying any more flats.

If anybody wants some I have 100 standard flats with rails for $14.25 each plus whatever shipping would be.
Ok, I'm going to try using the Tapco flat without welding the two rear trunion holes and see how it works out. It doesn't look like it will catch on the holes since the two pieces that rotate are pinned together and "shouldn't" try to move in and out independently. Then the other factor would be if the folder would cover the holes that are there if they weren't filled in.

After I get that all figured out I'll see what it would take to make one specifically for an AMD-65. Especially since the rear trunion holes are different plus the cutout for the folding stock.

Any other requests for something different that you don't see all over the web?
If I were to take the time to modify the flats they would be about $30 to $35. There are several tooling changes plus welding to be done on the flat.

I've never seen the AK-100 folding stock setup so I don't know what it would take to modify one for that.
That probably wouldn't be too horrible to try and modify a flat for. The one side with the slot would have a small radius on the back edge though. I would have to have one here to work with to really know what it would take to get them done.
For a one-off thing just making a template and marking it off would be the way to go.
Looks like I can start making up those modified flats now. They will work without welding up the two trunion holes since it doesn't affect how the stock folds up. If anything only one side would need to be done, but welding and grinding on the flats would take quite a bit of time in the end. If somebody wants to weld them up once they get them then that should work. You can't really see the holes either so it's not a real cosmetic issue either.

Last night I made up about seven of the flats and bent two of them to make sure they work fine. Today I sent one to somebody that lives fairly close so I can get somebody else's opinion of how it worked out.

If anybody wants one let me know and I'll start making up some more. Right now I've got three ready to go for $35 each plus shipping.
I spent most of my time trying to get to where I could reproduce the same piece over and over. Maybe when I get rid of all of the flats I have there might be a market for a steel template so you could just clamp the flat to it and dremel out the large hole and drill the others....


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