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Thread: Brazilian URU kit

  1. #1
    Gunco Member gary41's Avatar
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    Default Brazilian URU kit

    Does anyone know the thread size for the URU smg tube to screw barrel assembly on?
    Or does anyone have A print?
    Or does anyone have A demilled receiver.
    I have the barrel with threads but they or inside diam. And Ican't figure out how to find out what they are.
    I would like to put an undersized tube on this kit if I can figure out The thread size.
    Thanks

  2. #2
    Gunco Veteran Viper Dude's Avatar
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    Hello gary41,
    A suggestion to determine the thread size needed for your Uru kit...

    Use a white Q-tip stick (no cotton) to make a rubbing across the inside threads. The dirty grease etc will leave hash marks on the stick. Make several different rubbings untill you get a measurable one. A metric ruler (scale) then can reveal the pitch. My guess is that the pitch is either 1.0 or 1.5mm.

    Diameter measuring follows.

    What I suggest is a snap guage device aka telescoping guage that will transfer the female thread crest diameter to your mic. Knowing the 60 degree thread pitch you can calculate the thread depth. Double that depth to add to the ID measure. Presto !! You have the male thread size.

    I think that the equation is: thread Depth = pitch x cos 30 deg = 0.866 x pitch. Multiply that depth x 2 + ID = male OD. This assumes full threads are used. If the original inside (female) thread is truncated to say 90% then your newly threaded part will be tight. Put it back in the lathe, recover the phase, and turn the male thread a bit deeper with care.

    If you get really lucky the thread used may be a metric axle thread like 1.5-22mm (also an Egyptian Hakim barrel thread by the way). Those dies can be found in some auto parts or industrial hardware stores. Otherwise you will need a lathe to make the rare threads.

    Hope this is understandable and useful.

    VD

    PS: you know you are getting old when putting away your favorite gun book the cover crumbles !!!
    Last edited by Viper Dude; 03-11-2010 at 03:34 AM. Reason: added info.

  3. #3
    Gunco Member gary41's Avatar
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    Thanks viper dude, That was really helpful info I never would have thought of that system.
    Thanks again.

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