PC case and radiator fan mounting screw size
M3 · 25 to 35 mm long
The screws used on PC case and radiator fan mounting are M3 in lengths from 25 to 35 mm.
Where it is used: 120mm/140mm fans typically take M3 mounting screws; thicker frames and some radiator kits use M4.
This entry is marked reported and comes from graphicscardhub.com.
For reference, M3 is 3 mm across the threads at 0.5 mm pitch. The imperial size people confuse it with: #5-40 (3.18 mm) or #4-40 — neither interchanges with M3.
PC case and radiator fan mounting screw specifications
One row per fitment record. Head, drive are shown only where the source states them; pitch is the ISO coarse pitch for the thread.
| Thread | Length | Pitch | Head | Drive | Where it goes | Status |
|---|---|---|---|---|---|---|
| M3 | 25–35 mm | 0.5 mm | not stated | not stated | 120mm/140mm fans typically take M3 mounting screws; thicker frames and some radiator kits use M4 | Reported |
Fitment records and sources
120mm/140mm fans typically take M3 mounting screws; thicker frames and some radiator kits use M4
pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10
How to check the screw before you buy
- Laptop covers and brackets often mix two or three lengths of the same thread, so lay the screws out in the order they came out (a magnetic mat or a sheet of paper with the hole pattern drawn on it works).
- Diameter: across the threads an M3 screw measures about 3 mm with calipers (usually a hair under). If yours measures noticeably more or less, it is a different thread.
- Pitch: 0.5 mm from one thread crest to the next (20 crests per centimetre). A thread pitch gauge or the pitch-gauge tool settles it in seconds.
- Length: measure from under the head to the tip for pan, button, wafer and cap heads; countersunk (flat) heads are measured overall.
- The records span 25–35 mm, which means different positions take different lengths — match each hole to its own screw.
- Driver: the source does not name the drive. Standard M3 heads take PH1 for Phillips and T10 for Torx, and a 2.5 mm hex key for socket heads; a bit that fits loosely will cam out and strip the head.
- Tightening: no device-specific torque is published in these records. The site's general figure for M3 is about 80-130 N·cm into metal threads and 35-60 N·cm into plastic bosses; snug it up and stop.
Common mix-ups with M3
- Model rocketry altimeter manuals (Apogee AIM USB, Rocketronics AltiMAX G4, RockeTiltometer) contain no explicit metric screw thread callouts in their documentation; mounting is typically via hook-and-loop or generic standoffs, so no metric fitment can be confirmed for this category.
- PC cases mix M3 (fans, optical and 2.5in drives) with imperial 6-32 (3.5in drives, motherboard standoffs) - don't force one into the other.
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Devices whose records share a thread with PC case and radiator fan mounting, closest length match first.
- PC case & radiator fans also M3 × 25–30 mm
- PC case fan mounting screws (aftermarket kits) also M3 × 25–30 mm
- Pumpkin CubeSat Kit (PC/104 stack) also M3 × 25 mm
- PC case fan mounting (120/140mm) also M3 × 25–30 mm
- PC watercooling radiator fan screws also M3 × 25–30 mm
- VEX / Actobotics channel and gussets also M3 × 25 mm
- Prusa MINI frame and extruder also M3 × 25–35 mm
- Ubiquiti UniFi AP ceiling mount also M3 × 25–35 mm
Questions about PC case and radiator fan mounting screws
- What size screw does PC case and radiator fan mounting use?
- M3 × 25–35 mm for 120mm/140mm fans typically take M3 mounting screws; thicker frames and some radiator kits use M4.
- How long are the screws in PC case and radiator fan mounting?
- The records range from 25 to 35 mm depending on the position, so match each screw to its own hole.
- What is the thread pitch of an M3 screw?
- 0.5 mm (coarse), which is the standard pitch for M3 machine screws; a 0.35 mm fine pitch exists but is uncommon. The tap drill is 2.5 mm and the normal clearance hole is 3.4 mm.
- What screwdriver do I need for PC case and radiator fan mounting?
- The sources do not name the drive. For M3, Phillips heads normally take PH1 and Torx heads T10; socket heads take a 2.5 mm hex key.
- Can I use an imperial screw instead of M3?
- No. Imperial look-alike: #5-40 (3.18 mm) or #4-40 — neither interchanges with M3. Use a true M3 screw so it does not cross-thread or strip the hole.