What size thread and pitch are PC screws?

MikeHunt79 · 28 Aug 2008 at 19:18

I mean the screws that hold in hard drives, opticals, gfx cards, etc.

It's all a standard size thread.

It's not 3mm, too small

It's not 3.5mm, it's close (not not right)

4mm, too big.

I have a feeling it's something imperial.

I need some coutersunk screws, so if anyone knows the size I can order some.

fornowagain · 28 Aug 2008 at 19:26

UTS 6-32 (Unified Thread Standard) is very common on computers, similar to M3.5 in diameter. M3 is the finer ones on the floppy drives etc.

UTS > UNC-UNF-UNEF is the three pitch they use, 32tpi at #6 is course so UNC.

Order #6 (0.138") UNC (32tpi).

MikeHunt79 · 28 Aug 2008 at 20:09

Nice one, that's gotta be it, it's definately not M3. Thanks.

MikeHunt79 · 28 Aug 2008 at 23:13

I've searched and searched, but I can't seem to find anyone who stocks them! I've only found taps and dies. I've also tried screwfix, toolstation, etc. No joy. Do you know of a place (that isn't a competitor) that has them?

tigerstyle · 29 Aug 2008 at 00:10

I'm guessing no one makes them counter sunk as no one uses them? could be tricky!

whats the use anyhoo?

Cob · 29 Aug 2008 at 00:14

Tried the auction site?

fornowagain · 29 Aug 2008 at 13:55

You'll have more luck with countersunk socket screws, eg 6-32 x 1/4" , 2mm allen key

http://www.modelfixings.co.uk/unc_countersunks.htm

leezer3 · 29 Aug 2008 at 14:28

Model (Engineering) bits places are probably your best bet.

-Leezer-

MikeHunt79 · 29 Aug 2008 at 18:43

Cob said:
Tried the auction site?

Totally forgot about that, I just tried looking and found a few, along with some size 6 (32) womens clothing.

fornowagain said:
You'll have more luck with countersunk socket screws, eg 6-32 x 1/4" , 2mm allen key

http://www.modelfixings.co.uk/unc_countersunks.htm

Allen key is perfect, in fact I prefer them as they don't round out as easily. Thanks.

Greenlizard0 · 29 Aug 2008 at 18:53

Try the MM fella, I'm sure somebody will be happy to offload a few of their spare screws lying about?

PhillyDee · 29 Aug 2008 at 19:56

Heh. I made loads of these in stainless for thumbscrews. Still got 30 or so in the house. This was when they were just appearing but were £4-5 for 4.

Cheers for that link, thats going on my favourites!

MikeHunt79 · 29 Aug 2008 at 21:18

I've ordered them now, some pan head ones also, as I have lots of heatsinks with this threading.

littledave · 29 Aug 2008 at 22:01

What about some 3.5,, socket screws, they are the ones that hold you mains plug sockets ands light switches on, you can also cut these to length with a decent pair of side cutters

I have used these with no problem before, a bit tricky to get started but they fly in.

PhillyDee · 29 Aug 2008 at 22:11

Its always best to use the right screws. Especially since 6-32 is a coarse thread, and the electrical socket ones are a fine thread.

MikeHunt79 · 29 Aug 2008 at 22:44

^ Already tried the 3.5mm ones, went in about half a turn then stopped.

I really need them to be the imperial (UNC?) thread... It's for an old American PA amp which I'm fixing up... It's made by Crest Audio, and it had blown power caps and a few missing screws. A lot of American things still use imperial....

I tried all the screws I had lying around, and after try all the M3, M3.5, M4, etc. I found a set of hard drive screws worked perfectly, but now they are all poking out the side as they aren't countersunk.

Getting the right screws for the job is far easier than drilling and tapping a new thread, even if the screws are a strange diameter and pitch.