Section 2: Receiver finishing

If you went with the 100% receiver proceed to "Demilling the parts kit". If you bought the bendable flat follow the directions that came with the bending jig and proceed to the next section. If you opted for the 80% receive blank here are some hints on how to finish it.

You will need the following tools:                                             You will need the following materials:

Drill press with vise                                                                    3 pieces of  6.500" x 1" x .125" steel stock

Dremel type tool with cut off discs                                            1 piece of 6.500" x 1" x .750" steel stock

Small hand files (Flat and round)                                                2 pieces of 5" x 1" x .250" steel stock

Drill bits: .375"  .200"  .156"  .276"  .250"                                 1 piece of 8" x .375" x .750" steel stock

Piece of wood 12" long by 1.25" wide and 2" tall                      1 2" long .250" bolt with a nut

Small center punch and hammer                                                 

Caliper

Vise grip pliers 

"C" clamp

Bench vise

The first thing to do is bond the template to the receiver blank (If it is not already done). to ensure that the template is straight and centered I fold it first on the bottom form lines. I secure the in place with a piece of tape at the front and back and then use a spray adhesive to bond the template in place.

Next you will want to form the piece of wood into a mandrel for drilling and cutting the receiver.

Now you will want to double check the placement of all of the side holes on both sides of the receiver.

The correct hole placement is very important and I highly recommend that you check and remark any holes that are not perfect. To measure the placement go from the top of the rail to the center of the hole being sure to add the thickness of the receiver to the total. The correct measurements are as follows:

Safety selector  .550"

Trigger pin  1.380"

Hammer pin  1.100"

Center support  .750"

If your receiver is .040" thick you would add that to each measurement for the correct placement. Once you have all of the holes center punched you can drill them out. Drill the holes from each side, do not try to drill through as this may cause misalignment. 

Hole diameters:

Right side                                                             Left side

Selector large            .375"                                   .200"

Selector small            .200"                                   None

Trigger                       .200"                                  .276"

Hammer                     .200"                                  .276"

Center support           .200"                                  .200"

Next you will want to do the bottom cutouts. For the mag well drill the 6 .250" corners first and then use the Dremel with cutoff wheels to connect them. Be sure to cut UNDERSIZE and file to fit later. The trigger opening can be done as either a single or double hook style depending on which one you are using. Use the .156" drill to do the corners and Dremel cut the opening. Do the same with the pistol grip nut opening. Do not do the bottom rivet holes at this time.

This is what it should look like at this time. This is one of the Yugo underfold receivers I have done.

Now you get to make your fist custom tool. The AK receiver has mag centering dimples on both sides and a detent in the bottom front that need to be pressed in. Using the listed materials here is how to make these jigs. First you will need to drill a .250" hole through each of the .125", .250" and the .750" pieces of steel stock. The hole needs to be .625" in from the end and centered at .500". Two of the .125" parts will now need to have the punch guide slot formed. This is done by drilling 2 .375" holes on the center line. One at 2.1875" from the back and one  at 1.8075". Then you can use the Dremel and a file to create the top and bottom flats. I find it is easiest to vise grip the parts together and do them both at once to ensure that they match. The .250" parts will need to have the bottom outside edge beveled to fit into the corner of the receiver.

Now you will need to make the dimple punch. Using some of the .375" x .750" steel stock, Shape it with the file to look like the one below. Be sure to rebate the punch end to compensate for the thickness of the receiver.

When you assemble the jig on the receiver you will place one .250" on one side, the .750" part in the middle, The .125" part without the dimple hole next and one of the .125" parts with the dimple hole last. This is then slid into the receiver, The second .125" part with the dimple hole is then place on the outside and the assembly is bolted together by lining it up on the hammer pin hole.

Lock the assembly in place with a "C" clamp and use the anvil part of the bench vise to form the dimples with a hammer and ram. I use a piece of scrap wood as a wedge to hold the inside parts firm against the receiver.

If you rotate the punch several times for each dimple it will turn out more symmetrical. Once you have done one side reverse the jig and do the other side. Now you will do the front mag well detent using the two .250" parts and the .750" part. Set up the jig with the two .250" parts against the inside walls of the receiver and the .750" part in the middle about .375" in front of the mag well opening. You can use any type of scrap metal as the punch to make this detent. I modified a bolt head to do this on receiver blanks.

At this point you will want to remove the template from the receiver. I use kerosene but most any thinner will work.

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