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I have the unfortunate task of writing a technical document, and I know the government is a stickler for unnecessary detail. Is there standard name for the standard computer screw? Also, what is the name of the standard disk drive screw?

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Most screws in a computer are UTS 6-32 screws. 6-32 screws are used for your power supply, securing expansion cards, and the cas panels.

The other common screw type is the metric M3-0.50 screw, which are used for mounting optical drives, hard drives, and the motherboard.

To make it harder, there are also computer cases that ship with motherboard standoffs that accept imperial screws, not M3.

It's amusing that both imperial and metric screws are used in each computer, and rather annoying that these screws are fairly similar in size (although not in threading). This means that an M3 screw will fit in a 6-32 hole, and will even seem to screw in, but it won't stay in place well. A 6-32 screw will go in an M3 hole if you try hard enough, which results in stripping.

Note that the self-tapping plastic screws used exclusively for fans and some lighting are also standardized, although they're just standardized within industry as "self-tapping plastic screws" rather than being a standard mechanical screw size.

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Great answer but I disagree about case fan screws being standardized. I have four or five different kinds in my build box. They vary in thread pitch, shaft size, head size, some have a self-tapping gouge taken out of the tip. Woe betide anyone who tries to put one of the thicker ones into a fan with smaller-than-average holes. Because of this I prefer to use the black two-part plastic expanding rivets where possible. –  Adam Eberbach Aug 22 '11 at 7:18
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Oh wow, there's an entire WikiPedia article on computer screws... –  BloodPhilia Aug 22 '11 at 11:17
    
Isn't there one smaller than the M3? I recall trying to mount drives with some that I pulled out of my collection and they fit but wouldn't stay in place. They probably they came from external peripherals. I wonder if there's any standardization there? –  Matias Nino Aug 22 '11 at 14:09
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@Matias Nino: there are the laptop HDD screws which are tiny and have flat heads. –  Dani Aug 22 '11 at 14:17
    
No wonder I always want to impale people when I'm working inside my computer case and can never figure out which damn screw fits in the hard drive or only nearly fits. –  Chris Marisic Aug 22 '11 at 18:19
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6-32, and M3.

"Computer case screws"

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I thought they were all M3s.. which would explain some issue i've had in the past... +1 for enlightenment! –  Journeyman Geek Aug 22 '11 at 3:56
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