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American machine screw types

Discussion in 'Electronic Repair' started by N Cook, May 31, 2007.

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  1. N Cook

    N Cook Guest

    For period 1970 to 2000, whatever they are, they are not very common in
    Europe. Coarser thread , diam for diam, than the usual European mm and BA.
    Common sizes are about 0.132 in outside diam. , pitch 32 TPI, would they be
    UNC 6 ?
    and 0.11 inch od and TPI about 40 , would they be 4 UNC ?
     

  2. You need to try to find a copy of this handy little book:

    http://www.sequoiapublishing.com/pdt_pocketref3ed.htm

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  3. OK. The most common size is 6-32. 8-32 and 10-32 are also common. This is
    AWG size 6, 8 and 10 all with 32 tpi threads.

    Also 10-24 and 12-24 with 24 tpi are used.

    See http://www.zytrax.com/tech/mech/threads.htm for more.
     
  4. Bill S.

    Bill S. Guest

    Sounds like 6-32 and 4-40.
     
  5. N Cook

    N Cook Guest

    But are they what we call UNC ?
    and the 40TPI ones ? only measured with a ruler as my thread gauge, in
    inches, does not have 40TPI and the mm gauges are not close to any
    equivalent.
     
  6. See the chart on the web page.

    Also http://en.wikipedia.org/wiki/Unified_Thread_Standard
     
  7. Jamie

    Jamie Guest

    Now wait a sec.
    If you're comparing AWG size with screw sizes as above ?
    I think you have your wires crossed!..
    #6 wire is larger than #10 wire..
    6-32 is smaller than 10-32 screws.

    just an observation I made once long ago.
     
  8. Arfa Daily

    Arfa Daily Guest

    Years ago, I worked for an American computer equipment company, and used to
    have exactly the same problem with not being able to equate the screws
    fitted to the enclosures, to anything available in the UK. I won myself a
    right royal bollocking from the UK director of engineering, after I had been
    speaking on the phone to one of the design enginering staff in the U.S. I
    had phoned him to ask if we could get a stock of the case screws sent over
    to us. "Sure" he said. "I guess I could arrange that. What size are the ones
    you want ?" "Oh" said I, "about three sixteenths APF". "APF ?" said he.
    "What's APF ?" "Why, American Piss Fit of course !"

    Well, I *was* new to the game and only young. I didn't know much about
    America and the good people who live there, and just assumed that our humour
    was the same. Didn't do anything like it again though ...

    Arfa
     
  9. Which wire guage?
    Correct. In fact see http://www.tecratools.com/pages/service/taps_dies.html
    for the 24111 Tri-Tap Tool, which taps 6, 8 or 10 size holes at 32 tpi.
     
  10. Smitty Two

    Smitty Two Guest

    UNC is a coarse thread. UNF is a fine thread. UNEF is an extra fine
    thread. 2-56, 4-40, 6-32, 8-32, and 10-32 are common, but many others
    are prevalent as well, including the "odd" numbers, e.g. 3-48.

    It's worth noting that 6-32 is a UNC thread while 10-32 is a UNF thread.
    The "fine" version of a #6 screw is 40 TPI; the "coarse" version of a
    #10 is 24 TPI.

    And of course, it goes without saying that the obstinacy of my fellow
    Americans, clinging absurdly to a ridiculously clumsy system of
    measurement, is pathetic.
     
  11. Only nation on earth still not using metric, no?


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  12. N Cook

    N Cook Guest

    Perhaps APF screws in aeronautics
    This flight would have flown over me , not that I would have been aware that
    the pilot was hanging out of the cockpit.

    http://www.bbc.co.uk/dna/h2g2/A20460782

    "The subsequent inquiry revealed that the windscreen had been replaced just
    24 hours before the flight, and a number of errors in the procedure resulted
    in the wrong size bolts being used to fit the new window. Although the
    difference in size was minimal, some 200th of an inch, it was enough to
    cause the windscreen to blow out when the pressure differential became too
    great between the cabin and outside atmosphere."

    At least when I'm hunting for the 1% or less of "American" screws in my pile
    of salvaged mm and BA screws the coarse pitch makes them stand out in
    comparison. I still don't know if its safe to go out and get a pack of 6-32
    and 4-40 UNC machine screws for American equipment, where someone has been
    there before and not replaced all.
     
  13. Smitty Two

    Smitty Two Guest

    That's what I think, but not sure. Let's see, our cars now come with
    speedometers that can be switched to indicate km/hr instead of mph, and
    liquor is sold in liters instead of quarts. That's the sum total of
    fifteen or twenty years' worth of effort to go metric.
     
  14. Smitty Two

    Smitty Two Guest


    That's what sheet metal screws are for. Substitute 'em for anything!
    Anyway, you can't just get one pack. You've got to have pan head, flat
    head, oval head, button head, and socket head, at least -- not counting
    different lengths.

    Seriously though, Americans don't make consumer electronics anymore.
    It's all made in China. Metric for sure.
     
  15. We're fairly used to UNF and UNC in the UK as they were much used on cars
    before metric came in - but only really in the larger sizes. For small
    stuff Lucas ;-) stuck to BA.

    But I still see AF and AC taps and dies around - are the two versions
    still used? I realise there's not a vast difference - only basically
    thread profile.
     
  16. Bill S.

    Bill S. Guest

    It should have gone without saying. But let me turn that on its head:

    While the rest of the world clings pathetically to the idea of forcing
    a single tyrannical system on everyone, Americans have freely embraced
    the idea of duality. We have plenty of legacy equipment that still
    works perfectly well and needs support, and when making new we can
    choose whatever fits best. There are a few "clingers", but most of
    us just saw the metric system as additional options to use at will,
    not as a mandatory replacement. Mechanics have tools for both systems
    and not only switch freely between them, but take extra advantage from
    the wider range. A couple examples: a 12mm wrench will probably work
    on that 1/2" bolt head that's partly rusted away; a 1/4" bolt will
    probably fit that 6mm hole you just stripped out.

    The bottom line: not only are Americans now fully fluent with metric
    and decimal measurements, but we are also still fluent with fractions
    and SAE, *and also* familiar with conversions and inter-relationships
    between the systems. We have the best of both worlds and then some.
     
  17. Smitty Two

    Smitty Two Guest


    Oh yeah, I keep forgetting that you used to be in this mess with us.
    Terms with which I'm not familiar...
     
  18. Smitty Two

    Smitty Two Guest

    Fully fluent? Most Americans can't read a ruler anymore. Nor can they do
    third-grade arithmetic, or construct a sentence in the English language.
    You might be fluent, and I might be, but stupidity and ignorance are
    rampant. Kids now can't even tell time on an analog clock, and don't
    know what "clockwise" means.

    And this is hardly a time to be calling other countries "tyrannical,"
    while our administration is hell bent on absolute world domination.

    Sheesh, hope I'm disagreeing without being disagreeable. Been under some
    stress lately.
     
  19. American Fine and American Course.
     
  20. Smitty Two

    Smitty Two Guest

    If those are predecessors to UNF and UNC, I don't think anyone's using
    them anymore... The only other thread standard that we have that I know
    about is the pipe thread, NPT.
     
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