How long are the screws in Prusa MK3S extruder?

The records range from 10 to 40 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 Prusa MK3S extruder?

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.

Where can I buy replacement screws for Prusa MK3S extruder?

TechSpareWarehouse (our own store) lists M3 x 10mm, M3 x 12mm and M3 x 14mm, which match lengths in the records above.

Prusa MK3S extruder screw size

M3 · 10 to 40 mm long

Our records put Prusa MK3S extruder on M3 screws in lengths from 10 to 40 mm.

Where it is used: extruder body, idler and Bondtech gear assembly are M3 throughout.

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.

Prusa MK3S extruder 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	10–40 mm	0.5 mm	not stated	not stated	extruder body, idler and Bondtech gear assembly are M3 throughout	Confirmed

Fitment records and sources

M310-40mm (idler M3x40, body M3x10-18)confirmed

extruder body, idler and Bondtech gear assembly are M3 throughout

pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10

Source

How to check the screw before you buy

Into printed plastic, the screw either self-taps or needs a heat-set insert; machine screws straight into plastic strip easily.
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 10–40 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

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.
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.

Pitch gauge · Screw size finder · Torque guide

Buy these screws at TechSpare Warehouse

In stock and shipped from South Carolina. Our black screws are Phillips wafer head (low profile); match the head style and length to the original before you order.

M3 x 10mm Phillips Wafer Head Screw for Sim Racing Wheel Paddle Shifter - Single Replacement Black $0.10 each · min. 50
M3 x 10mm Phillips Wafer Head Screw for RC Car/Truck Chassis Mount - Single Replacement Black $0.10 each · min. 50
M3 x 12mm Phillips Wafer Head Screw for Camera Cage & Battery Slide Mount - Pack of 50 Black $6.49
M3 x 12mm Phillips Wafer Head Screw for Electric Scooter LCD Dashboard - Single Replacement Black $0.10 each · min. 50
M3 x 14mm Phillips Wafer Head Screw for Camera Cage & Battery Slide Mount - Pack of 50 Black $6.99
M3 x 14mm Phillips Wafer Head Screw for 3D Printer Extruder Stepper Motor - Single Replacement Black $0.10 each · min. 50
M3 x 10mm Phillips Wafer Head Screw for 3D Printer Frame Assembly - Single Replacement Black $0.10 each · min. 50
M3 x 12mm Phillips Wafer Head Screw for RC Car/Truck Chassis Mount - Single Replacement Black $0.10 each · min. 50

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The same screw also fits

Devices whose records share a thread with Prusa MK3S extruder, closest length match first.

Bambu Lab AMS unit also M3 × 10–16 mm
Voron 2.4 / Trident printed parts also M3 × 10–30 mm
Voron 2.4 gantry and panels also M3 × 10–25 mm
Prusa i3 MK3S/MK4 printed parts and extruder also M3 × 10–40 mm
E3D V6 hotend fixing kit also M3 × 10 mm
RatRig V-Core 3.1 (300x300) also M3 × 12 mm
Prusa MINI frame and extruder also M3 × 10–40 mm
2020 extrusion T-nuts (light duty) also M3 × 10–16 mm

Questions about Prusa MK3S extruder screws

What size screw does Prusa MK3S extruder use?: M3 × 10–40 mm for extruder body, idler and Bondtech gear assembly are M3 throughout.
How long are the screws in Prusa MK3S extruder?: The records range from 10 to 40 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 Prusa MK3S extruder?: 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.
Where can I buy replacement screws for Prusa MK3S extruder?: TechSpareWarehouse (our own store) lists M3 x 10mm, M3 x 12mm and M3 x 14mm, which match lengths in the records above.

Heads up: shipping delay