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FUBARed my AK SBR rear trunnion... 12 or 20 ton shop press?

Discussion in 'Maintenance & Gunsmithing' started by Stomper, Jun 4, 2012.

  1. Stomper

    Stomper Oceania Rising White Is The New Brown Silver Supporter

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    Hey folks,

    First a little background info...

    I recently received my NFA stamp to SBR my Draco-C, and found out the hard way the rear trunnion (was an underfolder at that) is SUPER HARDENED to rediculous levels (I have heard testimony of the hardness of these trunnions). I was finally able to get the holes drilled for the ACE folding stock, and proceeded to SLOWLY thread the holes for #10-32 mounting screws, but alast with a mere 1/8" left to thread, the tap broke off in the hole with no way to get it out without trashing the trunnion and receiver. I drilled out the LONG rivets & removed the rear trunnion, and chucked it out.

    I have a replacement trunnion, rivet kit, and rivet setting jig being delivered this week, but don't want to smack on it with a 3# hammer to form the rivets, hence I figure its time to invest in a HF hydralic shop press. I may get into AK "scratch" building... then again maybe not. I'm looking for input on either getting a 12 or 20 ton press. The 12 is on sale for $129, and the 20 is on sale for $169 this weekend at HF.

    Is the extra money worth it? Is a 12 ton adequate for busting out subborn barrels from AK parts kits? Lemme know what ya'll think. :thumbup:
     
  2. sheepdip

    sheepdip Redland Well-Known Member

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    dont bother with a HF press the frames will twist long before you get to advertized pressure
     
  3. cetme

    cetme oregon city Member

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    get yourself a drive time,or other free publication and use the harbor freight 20% off coupon on top of the sale price. :)
     
  4. Trailboss

    Trailboss Vancouver, WA Well-Known Member

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    Stomper, years ago I apprenticed in a metal working shop. Setting steel and aluminum rivets was a daily part of the job. The quality of rivet set with a hammer and set or a pneumatic rivet set is generally higher quality than a press. Put some gorrilla tape around the rivet in case of accidents and go carefully. A ball peen hammer is made just for this purpose and the rivet set is finished off with a steel set or flat steel punch.
     
  5. Stomper

    Stomper Oceania Rising White Is The New Brown Silver Supporter

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    Thanks for the input so far! Trailboss, thinking through the physics of the process I hear what you are saying about higher quality setting of the rivets with a hammer & set, thanks!
     
  6. eganx

    eganx Kingston WA Active Member

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    I set the rear trunnion rivets with a hammer and punch, have never had any issues, and can form a nice rivet head. Get a 5/16 ball endmill and a 5/8 grade 8 bolt, chuck the endmill up in a drill, and cut the rivet head recess on the threaded end of the bolt. Easy peasy with great results.


    0606121009.jpg

    BTW, I do have a 20 ton HF press but only use it for front trunnion and trigger guard rivets, and I'm sure the frame will not hold up to 20 tons.

    0606121009.jpg
     
  7. haji

    haji Oregon Member

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    Wow, I just did the same thing, broke the tap off in the hole...
    What did you ever work out?

    Thanks,
    Haj
     
  8. 44mag2ndamend

    44mag2ndamend Round the ole tree stump, Down by the crick Well-Known Member

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    Yeah, Harbor Fright stuff is like that.

    Made from old refrigerators, washers, dryer, ac units. Wonder how they came up with any ASTM standards on most of those metal products sold there.
     
  9. rick benjamin

    rick benjamin USA, Or, Damascus Secure the drama Silver Supporter 2016 Volunteer

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    Broke a tap?
    Use a center-punch and hammer.
    A firm smack will shatter it.
    Shake out the pieces.
     
  10. haji

    haji Oregon Member

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    Ok. I did that, got the tap out.
    Tried to just drill up to the next size tap, but the walls are super hard. I'm just burning the bits up.
    I welded together some mild steel and drilled some similar sized holes and am trying to "fill" the hole with filler rod. But not sure if there is a better solution...
    Any ideas?
    Sorry for threadjack/revival

    Thanks,
    haj
     
  11. KalamaMark

    KalamaMark Kalama Wa Well-Known Member

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    We just drilled a Zastava trunnion for a sling mount, and you're right, they are harder than the hubs of hell.

    It took a cobalt bit, lots of lube, and some pressure on the drill press. It was squeaky and smokey at the end, even with the lube. Good luck!
     
  12. haji

    haji Oregon Member

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    hubs of hell! ha!

    So were you successful threading it after that?

    Thanks,
    haj