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Computer standoffs - thread?

Does anyone know if there's a standard thread for the little brass hex standoffs as used for computer motherboards etc?

I'm modifying the controls for my CNC mill, and nipped into Maplins for something to use for mounting several small PCB's. The old Maplins cat that I keep had a good selection of such things, the new one in the shop shows virtually nothing. When I asked for 20 of what they have, I was told their computer showed they have only 10. OK, I'll take the ten. "Sorry, we haven't really got them, they were sent back for disposal as we're getting a new range". Of course, they haven't got the new range in before disposing of the old, that would be too sensible. The lad did find me some computer standoffs in a blister pack on the display racks, but the threads weren't marked and he hadn't a clue what they were. The female thread takes a standard M3 screw, but the male thread is about 3.5mm OD and 28tpi. Difficult to be sure with such a small sample. I wondered whether it's a hangover from the original IBM PC, but doesn't seem to match with any of the standard UNC threads, it would be 6 x 28 which I haven't found listed. Standard M3.5 threads are much finer, as is 4BA.

I need to tap the backplate to accept these, the nearest tap I have is

5/32 Whit (another oddball) which is too big, but I'll give it a try.

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech
Loading thread data ...

There are indeed US based threads and the metric stuff.

Can't remember what the US thread is, you'll find it on the older hard drives at the sides IIRC. I have a largish box of odds and sods of PC hardware that I can look through, and there are some M3/M3 hex spacers in there. M3 is for floppy drives and later HDD's.

Going to Birkenhead tomorrow, but I won't be able to come all the way down to your place as we are a bit tight for time, but if you want some of these bringing up and can meet me just off J11 on the M56....

(Got 6 of the M3/M3 X 6mm male/female types if you want them)

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

Could this be 6-32 UNC perhaps? The major diameter of this at 0.138" is 3.5mm all bar 2 thou. Theres a list of these odd american gauge sizes and equivalents here:

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Peter

P.S. Very pleased with the motor, thanks.

Reply to
Peter Neill

I think on reflection they are most likely a poorly made 6-32, though they're closer to 28 tpi according to my thread gauges.

I've tapped a few holes to 5/32" Whit (also 32 tpi), this gives a very sloppy fit in the (2.5mm thick?) backplate but huge mechanical strength isn't needed. A drop of Loctite on each thread should make a serviceable job.

Thanks Peter & Peter.

Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech

American 6-32. Same thread also used on locking screws for D type connectors.

Jim

Reply to
pentagrid

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