Original Prusa MK4 3D printer screw size
M3 · length not stated in the sources
The screws used on Original Prusa MK4 3D printer are M3. None of the sources we found gives an exact length, so measure the original before you order.
The record covers prusa's own assembly guide: most assembly screws are M3 (2.5 mm hex key), frame screws are M5 (3 mm hex key).
Head and drive, as the source states them: Hex socket (Allen) drive.
This entry is marked confirmed and comes from help.prusa3d.com.
An M3 screw is 3 mm in diameter with a 0.5 mm pitch, tapped with a 2.5 mm drill; imperial look-alike: #5-40 (3.18 mm) or #4-40 — neither interchanges with M3.
Original Prusa MK4 3D printer 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 | not stated | 0.5 mm | not stated | Hex socket (Allen) | Prusa's own assembly guide: most assembly screws are M3 (2.5 mm hex key), frame screws are M5 (3 mm hex key) | Confirmed |
Fitment records and sources
Prusa's own assembly guide: most assembly screws are M3 (2.5 mm hex key), frame screws are M5 (3 mm hex key)
pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10
How to check the screw before you buy
- Printer and CNC builds usually publish a bill of materials; when it lists a length, follow it, since extrusion T-nuts and motor faces have fixed thread depths.
- 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.
- Driver: the source names a Hex socket (Allen) drive. For comparison, standard M3 heads take PH1 (Phillips) or T10 (Torx), or a 2.5 mm hex key.
- 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
- GoPro's own official Dive Housing user guide does not itself state a metric screw size for the housing body; only third-party accessory manufacturer (INON) manuals explicitly cite M6 screws for their add-on arms/adapters attaching to the housing.
- Pond/aquarium equipment manuals aimed at consumers rarely specify exact thread pitch or length for internal fasteners, since these are considered non-user-serviceable; distributor-level assembly/service manuals (e.g., Maytronics internal documents) are a better source than end-user guides.
More in 3D Printing, CNC & Robotics
The same screw also fits
Devices whose records share a thread with Original Prusa MK4 3D printer, closest length match first.
- NEMA 23 stepper motor, 3A variant also M3
- Arduino Uno / Mega mounting holes also M3
- Carbide3D proximity switch upgrade kit also M3
- ESP32 DevKit boards also M3
- Prusa MK4 / MK4S kit also M3
- Arduino Mega 2560 mounting holes also M3
- Prusa MK3S/MK3.5 to MK4 upgrade kit also M3
- Ender 3 V2 hotend and hotend cover also M3
Questions about Original Prusa MK4 3D printer screws
- What size screw does Original Prusa MK4 3D printer use?
- M3 for prusa's own assembly guide: most assembly screws are M3 (2.5 mm hex key), frame screws are M5 (3 mm hex key).
- How long are the screws in Original Prusa MK4 3D printer?
- None of the sources states a length. Remove one screw and measure it from under the head to the tip (overall for a countersunk head).
- 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 Original Prusa MK4 3D printer?
- The source lists a Hex socket (Allen) drive. Standard M3 heads otherwise take PH1 (Phillips) or T10 (Torx), or 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.