Milling Torx into thumb pin for USC/UMP stock block B
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Thread: Milling Torx into thumb pin for USC/UMP stock block B

  1. #1
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    Default Milling Torx into thumb pin for USC/UMP stock block B

    This might not be the right forum for this question, but it's for a 'clone' of sorts -- my USC conversion. I used a UMP lower and the stock block sold at HK parts that allows you to use an ACR stock which I much prefer to the UMP stock. Anyway, I was pretty unstoked about the push pin that held it all together that required that key ring style pin to keep it in so I ordered the original HDPS thumb screw style pin for a stock block B. It works great BUT prohibits the ACR stock from folding. So, I took a grinder to the end with the sling attachment point since I'm attaching a sling a different way and I don't need it. I ground it flush and now it's out of the way, stock folds, happy face. Of course, now it's a pita to unscrew.

    To my question.

    Does anyone know where I might send said thumb screw pin to have a Torx type head milled into this flush end...maybe T25 or 30? I'm rural and pretty sure no one around here can do it.

    Thanks for any insights, move this wherever it's better suited if not here.

    Here are some pics of what I've done and what I mean. I'd like to have a torx head right in the center of that big shiny area..and then paint it black again.

    Milling Torx into thumb pin for USC/UMP stock block B-flat-2.jpgMilling Torx into thumb pin for USC/UMP stock block B-flat-1.jpg
    Last edited by bastardsonofelvis; 08-01-2017 at 04:29 AM. Reason: Pics
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    If you know the thread pitch, I can probably make a CAD file for you. You would be only a 3D print or machine shop away from what you want.

    ETA - and some accurate calipers. If the base pin is the same overall as a G36, then I can get the other dimensions from it.
    Last edited by Nzfly; 07-30-2017 at 12:42 PM.

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    Not sure on thread pitch, but could you use the regular USC screws?

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    Quote Originally Posted by fullmann View Post
    Not sure on thread pitch, but could you use the regular USC screws?
    Unfortunately no. They screw into the stock assembly that comes with th USC. It is threaded on the inside. The stock blocks for conversions are just pass through, and this pin has two halves that screw together.

    I didn't consider having another assembly machined but that's an option. Expensive though?

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    3D printing would be pretty inexpensive. I assume it is a low stress part. If so, it could be as cheap as $5. If you needed ultra high strength then it could be maybe $30 for carbon fiber or SLS nylon glass fiber. Making it out of aluminum would depend on if you were just charged at shop time.

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    Quote Originally Posted by bastardsonofelvis View Post
    Unfortunately no. They screw into the stock assembly that comes with th USC. It is threaded on the inside. The stock blocks for conversions are just pass through, and this pin has two halves that screw together.

    I didn't consider having another assembly machined but that's an option. Expensive though?
    I guess it's been a while since I did my USC/UMP conversion. My screws thread right into the block, I have the HDPS UMP block.

    Guess the new generation of blocks have a pin instead of screws.

    You could thread the inside of your block and use a helicoil to get the diameter down so you don't have to ream the receiver bigger

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    Quote Originally Posted by fullmann View Post
    I guess it's been a while since I did my USC/UMP conversion. My screws thread right into the block, I have the HDPS UMP block.
    Oh, that would be great. I think that would be ideal and provide a nice, solid lockup. Perhaps they tried to get fancy and make it user serviceable without any tools. The results are inferior stability, though, imo.

    You could thread the inside of your block and use a helicoil to get the diameter down so you don't have to ream the receiver bigger
    That's another way to skin the cat.

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    You could have a slot milled for a screwdriver or two small holes drilled for a dowel pin wrench. There is no way to mill a torx into the head.

    The head would look like this...
    Last edited by fasth2; 08-05-2017 at 08:53 PM.

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    I totally have an idea for this. Can you send me the pin and I'll send you back something that works for you?


    Also, you can mill a torx no problem. Just need tiny tools.

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    I would like to see a 20 or 25 torx milled .
    Show me.....

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