Screw You

bardin · 03-07-2003, 08:38 PM

Okay I've determinded that there's two different size screws (and in the process threaded who knows how many =), the larger threaded ones seem to be for cases, adapter cards, PSUs, and hard drives, and the finer threaded ones are for CD-ROM drives and floppy drives.

Anyone know WHY a CD-ROM and FDD would use a small screw but not a hard drive...?! I can understand why cases and PSUs use bigger ones.

Just out of curiosity.

Archibald · 03-07-2003, 10:02 PM

Actually there are three different sizes used (mainly). Can't answer why tho.

Terry Porritt · 03-07-2003, 10:03 PM

It's mainly historical. IBM is American, and they "invented" the PC so they used No. 6 UNC (Unified Coarse), 0.138" dia, 32tpi.

CDROM and floppy drives use M3 metric screws, but I'm not sure why the switch to metric, as the US abhors and cant understand metric, whereas Japan uses metric screws almost exclusively

Terry Porritt · 03-07-2003, 10:06 PM

............and yet, I have an old IBM 386 tall tower case that uses M4 screws for the case covers ?:|

Terry Porritt · 03-07-2003, 10:14 PM

I keep getting these afterthoughts

...........

It is a fact that the ISO metric screw thread system is not as satifactory as the older Imperial and US screw thread systems in respect of having fine and coarse threads.

There is a metric fine thread, but it is very rarely seen in everyday nuts and bolts. The "normal" metric coarse thread series is very much finer than the inch US and british counterparts and is very much poorer for thread applications in aluminium or cast iron. UNC and the Whitworth thread series were much superior in this respect, and also for sheet metal work threads such as computer cases where thread engagement is minimal to say the least.

I expect I'll think of more on the subject as my brain cells re-juvenate

Murray P · 03-07-2003, 11:31 PM

Keep going Terry, I'm interested.

Its always bothered me why different sized screws and threads are used with no particular logic in PC's as above some components use one type then another similar compnent will use something completely incompatible. It usually only seriously bothers me just after I've stripped the thread with the wrong screw in the right hole

, or should that be visa-versa?

I'm also interested in a way to avoid being bothered by it

bmason · 04-07-2003, 12:23 AM

The secret is to stop if the screw gives any resistance.

Having learnt the hard way, I now turn the screw using only the shaft of the screwdriver which makes it almost impossible to do any damage.

I also use thumb screws for frequently used ones to prevent stripping the thread.

Murray P · 04-07-2003, 12:35 AM

> I also use thumb screws for frequently used ones to
> prevent stripping the thread.

oOWww

Thomas · 04-07-2003, 09:54 AM

I thought this was interesting on threads.

http://www.team.net/sol/tech/whitworth-hist.html

Murray P · 04-07-2003, 10:53 AM

The plot thickens. Its a long time since I've done any tinkering with Brit cars or bikes. Normally we just put in what had come out, hopefully in the same place it came from then, there are VW's they definately had their idiosyncrasies. Jap bikes were much easier to get around and less oil on dad's drive, the odd pool in the garage tho

.

Back to puters. I think some of my problems have come from collecting screws from all sorts of different machines in a jar for safe keeping. Maybe I should get around to ordering them by type. The thread gage mentioned in the article would certainly help.

Cheers Murray P