108 - How to Insert Fitting Screw

Computer case screws are the hardware used to secure parts of a PC to the case. Although there are numerous manufacturers of computer cases, they have generally used three thread sizes.

Computer Chassis Screw

It is important to familiarise yourself with the difference between commonly used PC screws, as equipment can be damaged if the incorrect type of screw is used. If it does not screw in easily, it may be the wrong kind.


Fine Threaded Screw - Tricky to count, but will have around ten or eleven turns and is slightly smaller. The M3 screw has a pitch of 0.5 millimetres (0.020 in)

• Securing optical disc drives
• Securing hard disk drives (HDDs)
• Securing solid-state drives (SSDs)
• Securing floppy drives
• M3 screws typically accept a #1 Phillips screwdriver tip


Coarse Threaded Screw - Count the 'ridges' down the stem of the screw, coarse-threaded screws will have around four or five turns. The #6-32 UNC screw has a thread pitch of 1/32 in (0.031 in)

• To secure a power supply to the case
• To secure a 3.5 in hard disk drive to the case
• To hold an expansion card in place by its metal slot cover
• To fasten case components to one another
• Usually, a #6-32 UNC screw holds the main cover on the case


Case Fan Screws - Larger in diameter and having a more coarse thread than the standard screws, these are used to attach fans to the PC Case.

• For installing plastic-framed cooling fans to PC chassis

In all our instructions, we will try to help you use the correct kind of screw as per our experience. However, due to the enormous variety of PC devices we cannot guarantee that we will be correct in guessing the fixing type.

It is important not to force a screw fixing or over tighten it. If, when fixing a device, the screw does not rotate smoothly into place or gives any resistance to the movement, try another screw or another type of screw.

Tip: Screws fasten clockwise and unfasten anti-clockwise. To prevent 'cross threading' (when the screw thread damages the fixing hole and continually spins) try rotating the screw anti-clockwise a couple of turns, applying light pressure, until you feel or hear a slight 'click' this will indicate that the threads are aligned and that you can safely proceed to fasten the screw.

01 • Fine Threaded Screw

02 • Coarse Threaded Screw - Hex Head

03 • Coarse Threaded Screw - Pan Head

04 • Coarse Threaded Screw - Taper Head

05 • Fan Screw

06 • Thumb Screw

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