Page 1 of 3 123 LastLast
Results 1 to 10 of 24

Thread: thread size measurement

  1. #1

    thread size measurement

    Hi all. I have just acquired a new rifle and was assured that it had a 1/2 unf thread. Lovely I thought that will fit my mod i have already. Tried fitting it tonight and low and behold its the wrong thread size.
    So is there a way of measuring the thread without buying a special tool if one even exists.
    I have measured the screwcut section and from crown to face where the mod should stop is 14 mm. Is this measurement of use or do I need a diameter or count the threads etc.

    Also if a rifle is factory screw cut and then proofed is there a proofing stamp just near the action. Or if it is after market screw cut and then reproofed is there a stamp on the muzzle end of the barrel.

    All in all I'm a bit miffed as I was told it was factory screw cut ( not sure it was ) and half inch unf.
    Needless to say the dealer will be contacted. But in the mean time thanks in advance for your help.

    Also can I buy a different thread section for my a tec mod

    Regards Pete
    Last edited by pj1; 19-11-2014 at 00:19.

  2. #2
    It could still be 1/2 UNF

    maybe 1/2 x28 rather than 1/2x20 there's a few 1/2 threads used on muzzles but not sure of all of them

    if proofed after threading yes proof marks by muzzle

  3. #3
    Sorry to hear about the issue, what gun is it on. If its American like a Winchester, it could have a 1/2" UNEF or 28TPI.

  4. #4
    Its a cz 557 in 308. I will have another measure when I'm home.

  5. #5
    Distinguished Member Ronin's Avatar
    Join Date
    Oct 2014
    Lancs / Cumbria Border
    If the rifles been sold to you and the previous owner had it screw cut it has to have been proofed before sale.

    The PH usually mark the barrel at the shoulder of the screw cut (though not always)

    Easy to check thread - measure the diameter - if its .500" (1/2") then the thread will either be 1/2 x 20 Tpi or 1/2" x 28 Tpi (1/2" UNF or UNEF)

    You need a thread gauge to check this though (the TPi)

    It could be M14x1mm again - determine this by measuring the outside diameter of the thread.
    Last edited by Ronin; 19-11-2014 at 11:58.

  6. #6
    Can you take it to your local gunsmith/shop to see if they have a mod that screws onto it, at least that way you will find out what it is

  7. #7
    1/2" outside diameter thread options ---

    UNC = 13 TPI (Threads per inch)
    UNF = 20 TPI
    UNEF = 28 TPI
    BSW = 12 TPI
    BSF = 18 TPI

    Metric coarse threads
    12 mm outside diameter = 1.75 mm thread pitch
    14 mm = 2.0 mm
    16 mm = 2.0 mm
    18 mm = 2.5 mm
    20 mm = 2.5 mm

    Metric threads are often cut to different pitches to these standards so beware of that!

    Take your pick!

    Diameter is easily measured with a vernier caliper or micrometer
    Thread pitch / TPI are measured by using profile gauges - or by measuring the distance a nut travels along the screw when it is turned once.
    Go play!
    There is no substitute for measuring the items you want to fit!

    To complicate things some numpties can't use tools properly & machine threads badly & to wrong dimensions! - watch out for those!!

    Last edited by Yorric; 19-11-2014 at 11:12.

  8. #8
    Distinguished Member Ronin's Avatar
    Join Date
    Oct 2014
    Lancs / Cumbria Border
    Quote Originally Posted by Hornet 6 View Post
    ½"x30 ???

    Should that not be ½"x20 = UNF

    Fat finger error, sorted

  9. #9
    Quote Originally Posted by Redmist View Post
    If the rifles been sold to you and the previous owner had it screw cut it has to have been proofed before sale.
    Reflex Suppressors UK Proof Counsel's Opinion

  10. #10
    Thanks for all the replies. I will measure it again tonight. What has really wound me up is I bought a Schmidt scope for the rifle as I thought I wouldn't need a different mod. So now don't have the money for another mod and as I use the atec on my hornet it would mean buying two mods if I get rid of my atec due to different thread sizes

Similar Threads

  1. what thread size is my Sako 85?
    By jamesbilling in forum Rifles & Calibres
    Replies: 12
    Last Post: 05-01-2015, 18:01
  2. Thread size
    By JohnnyR in forum Rifles & Calibres
    Replies: 1
    Last Post: 17-03-2013, 20:44
  3. Warne Mounts thread size?
    By salukiwhippet in forum Equipment & Accessories
    Replies: 6
    Last Post: 12-02-2013, 18:04
  4. Thread cutting - what size?
    By charliefox in forum Equipment & Accessories
    Replies: 7
    Last Post: 17-01-2013, 21:37
  5. What Thread Size
    By gentleman jim in forum Rifles & Calibres
    Replies: 7
    Last Post: 12-03-2012, 23:02

Posting Permissions

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