Page 1 of 2 12 LastLast
Results 1 to 10 of 18

Thread: Any advice? Folded CETME flat won't accept the trunnion without gap in bottom seam

  1. #1
    Veteran
    Join Date
    Apr 2018
    Posts
    65
    Rep Power
    7

    Any advice? Folded CETME flat won't accept the trunnion without gap in bottom seam

    I've run a straightening mandrel through it, bolt carrier slides easily, and the seams match up pretty damn evenly, but when I insert the trunnion/barrel assembly, it forces open a gap in the forward bottom seam.(the flat is yet to be welded).I'm unsure of the best way to deal with this issue.

  2. #2
    holescreek's Avatar
    Join Date
    Oct 2009
    Location
    Centerville, OH
    Posts
    4,302
    Rep Power
    403
    I run my straightening mandrel through the receiver after it's welded. The mandrel isn't doing anything if the seams aren't closed.

  3. #3
    Veteran
    Join Date
    Apr 2018
    Posts
    65
    Rep Power
    7
    Thanks for replying...I was planning on running it through again after I get it welded up, I just wanted to run the mandrel through before to make sure that it's as close to correct as possible before it gets finalized together. The receiver is clamped together pretty securely at present time. I'm a little perplexed by it.

  4. #4
    holescreek's Avatar
    Join Date
    Oct 2009
    Location
    Centerville, OH
    Posts
    4,302
    Rep Power
    403
    I don't know how your mandrel works. Mine is designed to stretch the metal into it so that the receiver springs into the proper shape when the mandrel is removed.

    If everything else seems OK, weld it up then go to harbor freight and get an exhaust pipe stretcher/expander that fits the trunnion end and use it to round it out. The trunnion is usually a tight fit for me with my setup.

  5. #5
    Veteran
    Join Date
    Apr 2018
    Posts
    65
    Rep Power
    7
    I am using the mandrel sold by RTG. I believe it basically uses the same sort of principle. But a tube expander...!!! GREAT idea!! HF, here I come!!!

  6. #6
    holescreek's Avatar
    Join Date
    Oct 2009
    Location
    Centerville, OH
    Posts
    4,302
    Rep Power
    403
    I'm sure you're going to be careful and not over-expand, but I feel the need to bring it up anyway.

  7. #7
    Veteran
    Join Date
    Apr 2018
    Posts
    65
    Rep Power
    7
    No, believe me, I appreciate the word of caution!! I don't know if it will even be possible, as after your suggestion, I was researching exhaust tube expanders, and I'm wondering if a garden variety expander will even be able to muscle the 16 gauge steel enough. But I plan on finding out! I will utilize extreme caution, and I value your input!!

  8. #8
    Senior Veteran
    scottz63's Avatar
    Join Date
    Apr 2014
    Location
    Central Mo.
    Posts
    3,131
    Rep Power
    226
    Holescreek, great idea with the exhaust pipe stretcher/expander!
    14EH AIT Instructor-PATRIOT Fire Control Enhanced Operator/Maintainer

  9. #9
    holescreek's Avatar
    Join Date
    Oct 2009
    Location
    Centerville, OH
    Posts
    4,302
    Rep Power
    403
    I've never had to use one of the jigs HK sells but I gather from reading threads on several sites that they don't produce consistent results. It could be a design issue or maybe just the people using them with varying skill levels or available equipment. That was one of the reasons I never made bending jigs for sale. The trunnion diameter should be "built in" to the flat (meaning that if the flat comes together perfectly the diameter should be right), the old ORF flats I still use have perfect trunnion ID's after bending, and they were $25 flats!

    I just looked up the pipe expanders HF sells and the smallest one is 1.5". That's going to be very close to finished size. Another idea (and cheaper) would be to call your local AutoZone and see if they have one you can borrow.

  10. #10
    Veteran
    Join Date
    Apr 2018
    Posts
    65
    Rep Power
    7
    Yeah, Auto Zone might be a better option. Perhaps their tool might be of better quality. The inside of my flat in the trunnion area measures about 1.53 inches in diameter. Perhaps I need to sand the trunnion circumference a tiny bit...

Similar Threads

  1. SKS modified to accept AK magazines: Is it legal?
    By Poppa59HD in forum General Firearms Discussion
    Replies: 11
    Last Post: 11-01-2012, 09:13 PM
  2. I folded and started an AR
    By dpoe in forum AR-15
    Replies: 18
    Last Post: 09-09-2010, 05:06 PM
  3. flats folded finally
    By HKILLER in forum Cetme/HK
    Replies: 8
    Last Post: 12-28-2009, 07:11 AM
  4. WTB- Yugo Underfolder (bulging trunnion) flat&rails
    By the_shootist in forum Want to Buy
    Replies: 0
    Last Post: 03-09-2009, 11:57 PM
  5. WTS G3 flat & CETME barrel+trunnion
    By tony in forum For Sale
    Replies: 3
    Last Post: 02-12-2009, 05:57 AM

Bookmarks

Posting Permissions

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