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Screw threads

Discussion in 'Electronic Design' started by Dirk Bruere at NeoPax, Jul 5, 2007.

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  1. Hi

    Trying to find out what screw thread is used to fix hard disc drives
    into a PC chassis.
    I've sent an email to Seagate, but no reply so far.
    It seems a simple question but I just can't find the answer on the
    I do know that the thread is not the same as regular PC chassis screws
    even though the screw looks similar.
    Anyone know for sure?

  2. PeterD

    PeterD Guest

    6-32 in most cases. All other fasteners on drives are usually metric.
  3. Donald

    Donald Guest

    Did you try one ??

    Did it fit ??

    The screws for mounting a hard drive have not changed since 1985.

    I do know that one set of holes in the side of the drive is metric and
    the other set is standard(US).

    Is there a reason you need a real number ??

  4. MooseFET

    MooseFET Guest

    I've got several disks here. Perhaps they aren't the same model but
    I'll tell you what these use. All screw holes for mounting are
    standard #6-32. This makes sense because the casting is aluminum.
    You wouldn't want a finer thread than that into aluminum.
  5. Thanks for the replies - US 6/32
    The reason I need the thread is that I'm fitting HDDs into a custom
    carrier made from thick Al for heatsinking.
    The screws supplied with each HDD are not long enough, so I have to
    source ones a bit longer, ideally with countersink heads.

  6. It depends.
    There are two standards. 6-32UNC, and M3. Historically, drives made for
    the US market, had the former, while those made for the European/Japanese
    market had the later. You can even get the same drive, with both thread
    types from some manufacturers. I had 'joy' a few years ago, when having to
    source replacement drives in quantity, and the only ones available at the
    time, had the metric threads, where the originals sourced via the US, had
    the imperial threads...
    Generally 6-32, is the more common fitting on the 3.5" drives.

    Best Wishes
  7. krw

    krw Guest

    6-32 x 5/8", IIRC.
    Those are 2.5mm, or some such; much smaller.
    6-32 is definite, though 5/8" seems long.
  8. Eeyore

    Eeyore Guest

    Oh it's one of those funny US threads. 4-40 IIRC.

    They are the same screws as mainly used elsewhere in the case btw, although
    there may have a few instances where a metric therad was used by some

    3.5" floppies and CD/DVD drives use M3 screws btw.

  9. Eeyore

    Eeyore Guest

    6-32 is larger I think.

  10. Rich Grise

    Rich Grise Guest

    You use screws on your drives? I just lay them on that little platform. ;-)

  11. Rich Grise

    Rich Grise Guest

    Go find someone who has a thread gauge. :)

    Good Luck!
  12. Robert Baer

    Robert Baer Guest

    I have seen two types; US 6-32 and metric (slightly smaller, i think).
    Some drives allowed both types and most other drives take 6-32 only.
  13. Robert Baer

    Robert Baer Guest

    One can have as fine a thread as one wishes (say 80TPI max); the
    alloy makes no difference.
  14. In soft materials, you get greater ultimate strength using a coarse
    thread. This is why the 'standard', is to use coarse threads in soft
    alloys, and finer threads in harder materials. You can cut a fine thread,
    but for structural strength you want it coarser. Historically, the old
    'Whitworth' threads, were the result of quite a lot of research, trying
    different tooth shapes and pitches, to maximise strength in soft
    materials, and the UNC threads, are very close indeed to the same (in
    general, just changed the tooth shape to a 60 degree form, that is
    slightly easier to machine, than the 55 degree shape used on the Whit
    threads). The 'standard' metric thread (unless a pitch is specified), is
    actually the coarser of the metric normal forms, being reasonable for
    harder alloys, but rather too fine for soft aluminium. Stupidly, this is
    used as being 'easy' in a lot of places, despite it being less than
    If you look at the studs used on PC cases, those made by 'better'
    manufacturers, have a coarse thread on the stud designed to screw into the
    alloy case, and a finer thread on the inside to take the screw (cheaper
    manufacturers don't bother, and use the same thread on both parts...).
    Fortunately, in general, the actual strength needed in PC parts, is tiny,
    compared to the ultimate strength, so people 'get away' with poor thread

    Best Wishes
  15. Ross Herbert

    Ross Herbert Guest

    The information you are looking for is on the Seagate website.

    Go here and
    select for example ATA Hard Drives and you will find the screw size
    and thread.
  16. Here in Australia, things are dicier still. I've got two identical Seagate
    7200.10 drives, bought a couple of months apart from different vendors. One
    uses 6-32 screws, the other uses M3's. I've recently bought a few Samsung
    501LJ's and they all use M3's. The older SCSI drives I've got use 6-32's.
    Self-tappers and a strong screwdriver are starting to look enticing :)

  17. Jasen Betts

    Jasen Betts Guest

    6-32 UNC
    the other screw used is M3, it fits crdom drives etc...

  18. Jasen Betts

    Jasen Betts Guest

    Coarse threads work better in soft alloys for a number of reasons
    eg: less risk of stripping the threads or cross-threading.

  19. Eeyore

    Eeyore Guest

    Rubbish. I suggest you try cutting one.

  20. Robert Baer

    Robert Baer Guest

    Have done it a few times; no problems.
    Usually the finest i do is 2-56 tho.
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