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Thread: How to make a Cetme locking piece

  1. #1
    holescreek's Avatar
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    How to make a Cetme locking piece

    I wanted to try a 35 degree LP in my PSG1ish since I got my suppressor. It's been so long since I made a LP that I figured it's time to take some photos.

    Step one: Turn the backside diameters and cut to length. Leave material on the shank diameters for OD grinding. Drill the FP hole through.
    20170811_102746.jpg

    Step two: Flip it around in the chuck and use a form tool to cut the radius closest to the nose.
    20170811_121214.jpg

    Step three: Mill the sides flat in the mill leaving grind stock on the thickness.
    20170811_122715.jpg

    Step four: Mill the two roller relief radii (middle LP shown).
    20170812_135657.jpg
    Last edited by holescreek; 05-29-2018 at 06:00 PM.

  2. #2
    holescreek's Avatar
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    Step five: Set up the locking tab fixture on the rotary table.

    20170812_184141.jpg

    20170812_184130.jpg

    Step six: prep for heat treat. Stainless steel wire is used to remove parts from the furnace and get into the oil quench.
    20170812_194426.jpg

    Step seven: Heat the parts to 1550 degrees (O-1 tool steel) for 15 minutes and quench in oil. This nets an average Rc of 62-63. Place in a 400 degree oven for 20 minutes to temper and draw them back to Rc58-59.
    20170813_134000.jpg
    Last edited by holescreek; 05-29-2018 at 05:59 PM.

  3. #3
    holescreek's Avatar
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    Step eight: Glass bead prior to grinding.
    Step nine: Set motorized spin fixture up on the surface grinder and grind the shank to finished diameter (.430"). Side wheel the carrier shoulder to use for the angle grinding process.
    20170813_150705.jpg

    Step ten: Switch to the indexer and hold onto the ground shank. Indicate the flat sides parallel and grind them to the finished dimension (.312" total thickness).
    Step eleven: Rotate the indexer to grind the sides to lay against the angle fixture ramp (~.95" OAW).
    20170813_155356.jpg

    Step twelve: Make a fixture to hold the LP at the proper angle. This one is at 17.5 degrees to produce a 35 degree LP.
    20170813_165943.jpg

    20170813_185306.jpg

    Step thirteen: Grind the shoulder angles, checking against your master parts.
    20170813_190718.jpg

    20170813_185639.jpg
    Last edited by holescreek; 05-29-2018 at 06:09 PM.

  4. #4
    holescreek's Avatar
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    Eventually I'll get back to the range to give the 35 degree LP a test run with the suppressor. If I make a video I'll post it here. There are more than likely the only 35 degree LP's for a Cetme in existence.

  5. #5
    Senior Veteran sdk1968's Avatar
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    awesome looking work as always!

    cant wait to see you put it in action!
    say what you mean & mean what you say!
    TEC Tactical=SOT/07 i work there.

  6. #6
    Buckshot's Avatar
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    Wow, fascinating work - it would be great seeing a video of it in action
    Occam's razor, the simplest explanation will be the most plausible

  7. #7
    Senior Veteran weasel_master's Avatar
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    You are a true artist Holes.
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    In memory of Johnhttp://act.alz.org/goto/Weasel

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    Senior Veteran seasmoke's Avatar
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    Well done HC. Step seven... nice.
    METUS EST PLENUS TYRANNIS

    COG#2011

  9. #9
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    Incredible work, very impressive.
    The answer to 1984 is 1776.

  10. #10
    holescreek's Avatar
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    I probably won't be making many more locking pieces, in fact it's been so long since my last ones that I'd already mixed the form tool bits into the misc drawer and forgot some of the machining steps. Luckily I knew where the tab fixture was and was able to adapt it to the new old rotary table. I figure posting it here in a public forum for all to see would preserve the knowledge for the next group of builders who are up to the challenge. After all, it was members of this group that took part in the locking piece type study many years ago. The past few weeks I've updated all of my Cetme build tutorials on this site with photos downloaded directly to the site for the same purpose.

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