Screw threads

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 ??

donald

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.

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.

Dirk

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

Those are 2.5mm, or some such; much smaller.

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

Cheers! Rich

Go find someone who has a thread gauge. :-)

Good Luck! Rich

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.

One can have as fine a thread as one wishes (say 80TPI max); the alloy makes no difference.

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 optimal. 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 selection.

Best Wishes

screws

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

Go here

Here in Australia, things are dicier still. I've got two identical Seagate

the other screw used is M3, it fits crdom drives etc...

Bye. Jasen

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

Bye. Jasen

I guess I should have qualified that with "for the given bolt size" and it wouldn't have been misunderstood. Still into a casting a smaller bolt is not as reliable.

(snip)

I've often said "screw threads" as I brought out the riveting tool.

I would hazard a guess that the finest (erliable) screw thread one should do is 40TPI in casting.

I'm sure it depends on the casting but I've had #4-40 screws fail in a casting. We switched to a machined part.