Prusa Original MK4 Frame assembly structural screws screw size
M3 · length not stated in the sources
The screws used on Prusa Original MK4 Frame assembly structural screws are M3. None of the sources we found gives an exact length, so measure the original before you order.
It is listed for assembly manual: 2.5mm Allen key for most of the M3 screws on the assembly.
Head and drive, as the source states them: Hex socket (Allen) drive.
This entry is marked confirmed and comes from help.prusa3d.com.
M3 means a 3 mm nominal diameter with a 0.5 mm thread pitch. Imperial look-alike: #5-40 (3.18 mm) or #4-40 — neither interchanges with M3.
Prusa Original MK4 Frame assembly structural screws 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) | Assembly manual: 2.5mm Allen key for most of the M3 screws on the assembly | Confirmed |
Fitment records and sources
Assembly manual: 2.5mm Allen key for most of the M3 screws on the assembly
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
- 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.
- The bioprinter M3 reference is a tube-connector thread spec, not a structural chassis screw; verify before assuming interchangeability with fastener screws.
More in 3D Printing, CNC & Robotics
The same screw also fits
Devices whose records share a thread with Prusa Original MK4 Frame assembly structural screws, closest length match first.
- Prusa MK4 Nextruder also M3
- Voron 2.4 electronics bay also M3
- Voron Stealthburner toolhead also M3
- RatRig V-Core 3.1 X-axis assembly also M3
- Bambu Lab printers (common screw guide) also M3
- Ultimaker Original heated bed / Z-stage upgrade kit also M3
- NEMA 17 stepper motor mounting also M3
- OpenBeam / MakerBeam 15x15 mm extrusion also M3
Questions about Prusa Original MK4 Frame assembly structural screws screws
- What size screw does Prusa Original MK4 Frame assembly structural screws use?
- M3 for assembly manual: 2.5mm Allen key for most of the M3 screws on the assembly.
- How long are the screws in Prusa Original MK4 Frame assembly structural screws?
- 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 Prusa Original MK4 Frame assembly structural screws?
- 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.