Author Topic: AKM Underfolder Build  (Read 1881 times)

Offline hwong

  • Jr. Member
  • **
  • Posts: 69
Re: AKM Underfolder Build
« Reply #20 on: November 08, 2013, 12:34:50 PM »
Drilling front trunnion holes when bending your own flat.

Set up 1-2-3 block perpendicular to spindle. Clamp down tight to XY table. Clamp front trunnion tight to 1-2-3 block as shown about 3/8" above table making sure trunnion is perpendicular to spindle. Locate trunnion hole using a 5/32" bit. Slide bent receiver into front trunnion tight against 1-2-3 block and drill through as shown. Remove receiver and locate second hole. Slide receiver back onto front trunnion and insert rivet into first hole then drill through second hole. Repeat process for third hole. Before riveting make sure front edge of trunnion is even with front edge of receiver.

Offline hwong

  • Jr. Member
  • **
  • Posts: 69
Re: AKM Underfolder Build
« Reply #21 on: November 08, 2013, 12:47:15 PM »
Correcting improperly drilled holes in parts (may not apply to your particular kit)

The rear sight block pin hole was drilled by cheap labor as evidenced by the canted hole when I inserted a drill bit through the rear sight block. It was corrected when I drilled the barrel for pins, verified beforehand when I aligned and pressed into place.

Offline goober

  • Sr. Member
  • ****
  • Posts: 1632
    • goober on heatware
Re: AKM Underfolder Build
« Reply #22 on: November 10, 2013, 10:09:48 PM »
nice work, hwong!!!  :D
not a lot of AK build threads here on CNC Guns, and you've covered almost the entire build process well, including tool building!
great contribution  :D
heatware username: goober

Offline hwong

  • Jr. Member
  • **
  • Posts: 69
Re: AKM Underfolder Build
« Reply #23 on: November 11, 2013, 10:17:55 AM »
Thank you. I'm not on any other forum. Since I'm working on the AR-10 forging, I figure I would post the AK build here for members.

Offline kdkerr2

  • Jr. Member
  • **
  • Posts: 50
Re: AK Rivet Installation
« Reply #24 on: January 12, 2014, 07:05:59 PM »
I was shooting my M71 Valmet [a Finnish AKM clone] one day and it stopped firing. My front rivets had sheared off! And they were all stock from the factory. I assumed they'd got hold of a bad batch of rivets with bad alloy or bad heat treatment. I turned down some 1/4-20 socket head cap screws which all have good alloy and heat treatment usually and then I used an ordinary 100 ton hydraulic press to press them in. On the side with the rivets already installed I used a steel block with some holes drilled in it to give the installed rivets clearance so they wouldn't be marred. Worked well and so far the new homemade rivets have been holding up.

Offline hwong

  • Jr. Member
  • **
  • Posts: 69
Re: AKM Underfolder Build
« Reply #25 on: January 13, 2014, 09:18:49 AM »
Kdkerr2,
Whoever put together your AK clone did not dimple the sheet metal for the rivet holes by the mag well. Dimpling the sheet metal locks in the trunion when swell neck rivets are used for that last hole. Prevents front trunion from shifting. I use rivets from AK-Builder which have the correct swell neck rivets.

Offline kdkerr2

  • Jr. Member
  • **
  • Posts: 50
Re: AKM Underfolder Build
« Reply #26 on: January 13, 2014, 09:56:05 AM »
My Valmet was built at the Finnish factory. I can only assume the rivets were substandard, either the alloy or the heat treatment. I don't know that much about building AK's. I just shoot them.Valmet arms division had an excellent reputation.

Offline hwong

  • Jr. Member
  • **
  • Posts: 69
Re: AKM Underfolder Build
« Reply #27 on: January 13, 2014, 03:01:28 PM »
If the rivet sheared off you would have seen the rivet tail still lodged in the hole as the tail should have swelled on the back side of the trunion. If the rivet fell out there would be no rivet tail stuck in the hole since it was not installed properly. In my writeup I included pics of compressed rivet tails for the three trunion holes.

Offline kdkerr2

  • Jr. Member
  • **
  • Posts: 50
Re: AKM Underfolder Build
« Reply #28 on: January 13, 2014, 10:15:58 PM »
Chris Wiszowaty and I are making up machinist drawings for the Norinco MAK90 [forged receiver] and I need to know the shaft diameter of the rivets that hold the trigger guard and the cartridge guide [might not be the right name] at the front of the receiver just behind the chamber. Also the distance from the front of the receiver to the center of that last mentioned rivet hole would be nice too since I can't get the plate off that covers up that rivet to make that measurement.
Sincerely
Kerwin Kerr [kdkerr2]

Offline kdkerr2

  • Jr. Member
  • **
  • Posts: 50
Re: AKM Underfolder Build
« Reply #29 on: January 14, 2014, 12:22:43 AM »
The part I needed to know the diameter of the rivet for is called the bullet guide. I found the correct nomenclature at the K-Var website.