Results 1 to 9 of 9

Thread: UNS threads

  1. #1
    Join Date
    Dec 2003
    Location
    Regina and Assiniboia, Saskatchewan
    Posts
    5,950

    Post UNS threads

    Hey guys! So tell me...what is the UN series thread all about? What makes it different from other threads? Why can't I find taps in my KBC catalog? Seems the auto industry uses this thread for tie rod ends. Any idea why? I did a google search for this and found a few tidbits but nothing to explain the ins and outs. Any info on internal 7/8 X18 UNS thread cutting on a lathe? Thanks in advance!
    Russ
    I have tools I don't even know I own...

  2. #2
    Join Date
    May 2003
    Location
    52N 122W Western Kanuckistan
    Posts
    40,418

    Post

    UNS stands for UNified Special. Here is a table of sizes.

    http://www.whittet-higgins.com/thrddim.php?id=1

    They are basically bastard sizes.

    Here is another table that lists 7/8 X 18

    http://www.sizes.com/tools/thread_american.htm

    and another one. They have the same thread form as UNC and UNF.

    http://www.efunda.com/designstandard...148&finish=227

    Use your regular thread cutting tools and cut at 18 tpi.

    As to the "why" part I would assume it would give fine adjustment capability by using 18 tpi on a 7/8 shaft.

    [This message has been edited by Evan (edited 05-05-2004).]
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  3. #3
    Join Date
    Oct 2002
    Location
    Bremerton Washington
    Posts
    5,006

    Post

    There's good reason for UNS threads.

    One is that some applications force use of a special thread because of space - bearing nuts, threads used in optical apparatus, and measuring threads are but a few examples.

    Another is to force purchasers to use the manufacturer's replacement parts - a vile practice widely used in valves and switches.

    There's conservation of materials and weight savings.

    Note that the manufacturing data for UNS threads are claculated from the same formula as UNC and UNF threads. It's a consistant system that allows the design of screw threads over a wide variety of applications and sizes. Ingenious really, considering it was developed by a committee.

  4. #4
    Join Date
    May 2002
    Location
    Beaumont, TX
    Posts
    7,251

    Post

    <font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
    There's good reason for UNS threads.

    One is .......

    Another is to force purchasers to use the manufacturer's replacement parts - a vile practice widely used in valves and switches.

    .......
    .
    </font>
    And by manufacturers of measurement instruments and gauges like Starrett! And not just replacement parts but accessories also.

    **#%%**####!

    Paul A.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  5. #5
    Join Date
    Dec 2003
    Location
    Regina and Assiniboia, Saskatchewan
    Posts
    5,950

    Post

    Thanks for the info and links guys! Any idea where to get taps for this thread? I have a couple of pieces to do that are way too long for my lathe and won't fit through the headstock....Thanks.
    Russ
    I have tools I don't even know I own...

  6. #6
    Join Date
    Apr 2004
    Posts
    237

    Post

    KBC Tools, page 191, Part number 1-372-324, $37.12 Cdn each.

    http://www.kbctools.com/can/main.cfm

    Mike

  7. #7
    Join Date
    May 2003
    Location
    52N 122W Western Kanuckistan
    Posts
    40,418

    Post

    Russ,

    7/8 X 18 tpi KBC part number is 1-372-324

    Price is $37.12 cdn on page 191.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  8. #8
    Join Date
    Dec 2003
    Location
    Regina and Assiniboia, Saskatchewan
    Posts
    5,950

    Post

    Mike and Evan...Thanks! I actually did see that in there but wasn't sure if it was the right one. Sorta thought there might have to be a UNS designation there somewhere.
    I have tools I don't even know I own...

  9. #9
    Join Date
    Jul 2002
    Posts
    162

    Post

    Firearms makers have long been facinated by special therads. Scope mounting holes are either 8x40 or the more common 6x48 thds. The receiver ring is thin due to the barrel threads and hence the tighter thd.for the scope mounts. Instrument and tool makers follow the same theory. It just gives a little more bearing surface. They are however the pits to deal with if over tightened and the heads stripped off as some are wont to do!

Posting Permissions

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