Page 1 of 2 1 2 LastLast
Results 1 to 10 of 12

Thread: notebook: flap locking

  1. #1
    TRX
    TRX is online now
    Gunco Irregular TRX's Avatar
    Join Date
    Aug 2008
    Location
    Central Arkansas
    Posts
    2,763
    Feedback Score
    3 (100%)

    Default notebook: flap locking

    I'd looked at flap locking systems before, but though the bolts and flaps are simple, rugged, and easy to machine with conventional shop equipment, making the locking recesses in the receiver is a different problem. Also, I've never been able to examine a receiver from a flap-locked rifle, and so far haven't found any good pictures. The flap lock seems so nifty, but without a way to make the recesses in the receiver it's just a curiosity.

    One of those magic endmills that cuts around a 90 degree corner would sure help...

    Anyway, I was sketching some stuff this morning, trying to figure out if I could reach in through the barrel hole with a long end mill (no) or cut the receiver off into an AK-style trunnion and do it from the back with a keyseat cutter (no).

    With only some poor pictures of an RPD, it looks like the Russians used a big side cutter to make most of the recess, then cut a hole in the top rail and broached or shapered the end of the recess square.

    The British EM-2 used flap locks. Best as I can tell, the EM-2 receiver was stamped in left and right halves and welded together. It would have been easy to finish the stamped recesses before welding.

    If you bolted a receiver together with side plates like a 1919 a flap lock would also be easy.

    I doodled some stuff involving milled holes in the side of the receiver, where squared recess "buttons" could be pressed in and welded. That would work, but it lacks elegance.

    Then I had another idea - you could just tilt the receiver or cutter at an angle and mill the recess from outside, where you would end up with a big hole with the front and back edges slanted a bit forward, at whatever angle the flaps rested at.

    The front of the flap is restrained by the bolt, so it's not going to fall into the squared-out hole. The back of the flap needs to be stopped to keep it from flying out past the side of the receiver. A cover plate would work... or you could do an AK-ish trunnion and wrap it in a sheet metal receiver, which would be a fine cover plate.

    I have a scratch-build project ongoing with roller locking. The plan was to go to a conventional turnbolt lock if the rollers didn't work, but the flaps would be a better fallback.

  2. #2
    Gunco Veteran Viper Dude's Avatar
    Join Date
    Feb 2005
    Posts
    1,686
    Feedback Score
    0

    Default

    Hello TRX,
    The Russian DP series LMG's used flap lock recesses carved into the walls of the meaty receivers. These recesses appear to be done using a shaper cutting to a relief slot at the bottom of the stroke that serves as a chip breaker. I explained this process years ago to a local arms manufacturer who was intersted in a US Navy contract to produce Berretta pistol replacement slides. He originally wanted to use EDM to form those pockets but that process takes time - lots of time.

    A Bridgeport slotter head or a P&W verticle shaper would knock these pockets out quickly. Even a small bench top horizontal shaper can do this work.

    VD

  3. #3
    TRX
    TRX is online now
    Gunco Irregular TRX's Avatar
    Join Date
    Aug 2008
    Location
    Central Arkansas
    Posts
    2,763
    Feedback Score
    3 (100%)

    Default

    Would the shaper be approaching the pocket from the barrel hole or from the top?

  4. #4
    Gunco Veteran Viper Dude's Avatar
    Join Date
    Feb 2005
    Posts
    1,686
    Feedback Score
    0

    Default

    It's machined from the bottom (where the ejection port is) as is the small slitting saw on a mandrel that does the undercut. Pause here while I double check a DP-28 receiver chunk... the slitting saw disc appears to be about 1/2 inch diameter by .065 inch thick.

    The flap recess is: .820 inch tall by 0.100 inch wide (actually depth into side wall). The total shaper stroke into the receiver from the bottom: 1.410 inch.

    The actual shaper bit cuts a small squared pocket. The rest of the flap recess is carved out wth a small 1/2 inch diameter end mill with reduced shank diameter so it cuts the rest of the flap bevel inside the receiver.

    These observations are from a virtually brand new DP-28 receiver chunk (Polish made). That chunk has clearly visable tooling marks.

    VD
    Last edited by Viper Dude; 01-25-2011 at 06:43 PM. Reason: correct a decimal...

  5. #5
    TRX
    TRX is online now
    Gunco Irregular TRX's Avatar
    Join Date
    Aug 2008
    Location
    Central Arkansas
    Posts
    2,763
    Feedback Score
    3 (100%)

    Default

    Could you post a picture of that?

  6. #6
    Gunco Veteran Viper Dude's Avatar
    Join Date
    Feb 2005
    Posts
    1,686
    Feedback Score
    0

    Default

    Hello TRX,
    I'll try to get a decent picture of the locking recess. First I must make the darn camera work.

    VD

  7. #7
    Gunco Regular The Dark Knight's Avatar
    Join Date
    Jul 2008
    Posts
    554
    Feedback Score
    4 (100%)

    Default

    I have thought a lot about this too. I don't know how Wiselite did it but, the cut RPD receiver I have looks like the receiver was put on end and they used a long woodruff key to cut the recesses. Then the cut the top with another woodruff key to make it square.

  8. #8
    tired of idiots vz58's Avatar
    Join Date
    Sep 2006
    Location
    central NC
    Posts
    2,276
    Feedback Score
    25 (100%)

    Default

    Quote Originally Posted by The Dark Knight View Post
    I have thought a lot about this too. I don't know how Wiselite did it but, the cut RPD receiver I have looks like the receiver was put on end and they used a long woodruff key to cut the recesses. Then the cut the top with another woodruff key to make it square.
    Looking closely at mine it looks like a custom broacher was used then a woodruff

  9. #9
    TRX
    TRX is online now
    Gunco Irregular TRX's Avatar
    Join Date
    Aug 2008
    Location
    Central Arkansas
    Posts
    2,763
    Feedback Score
    3 (100%)

    Default

    Quote Originally Posted by Viper Dude View Post
    First I must make the darn camera work
    Look at it sternly and give it a good talking-to. If it's still uncooperative, threaten it with the Big Hammer.

  10. #10
    Gunco Veteran Viper Dude's Avatar
    Join Date
    Feb 2005
    Posts
    1,686
    Feedback Score
    0

    Default

    Hello TRX,
    I'm still wading through 290 pages of camera instructions and techno-crap so I can take a freaking picture !!! I should get a simple cell-phone-grade digital camera for this stuff.

    In the mean time I'm inletting my SVT-40 Tokarev shortie stock. I haven't done that sort of stock work since I was in highschool (50 years ago). Now I remember why I quit doing that !!!

    VD

Page 1 of 2 1 2 LastLast

Search tags for this page

There are currently no search engine referrals.
Click on a term to search our site for related topics.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •