How long are the screws in MGN9 linear rail?

The records range from 6 to 8 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 MGN9 linear rail?

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 MGN9 linear rail?

TechSpareWarehouse (our own store) lists M3 x 6mm and M3 x 8mm, which match lengths in the records above.

MGN9 linear rail screw size

M3 · 6 to 8 mm long

MGN9 linear rail takes M3 metric screws in lengths from 6 to 8 mm.

It is listed for countersunk bolts fixing the small rail to the frame.

Head and drive, as the source states them: flat / countersunk head.

This entry is marked reported and comes from hiwin.us.

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.

MGN9 linear rail 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	6–8 mm	0.5 mm	Flat / countersunk	not stated	countersunk bolts fixing the small rail to the frame	Reported

Fitment records and sources

M36-8mm countersunkreported

countersunk bolts fixing the small rail to the frame

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: the source describes a countersunk (flat) head, and those are measured overall, from the top of the head to the tip.
The records span 6–8 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

Eurorack rail thread varies by manufacturer: some tapped M2.5, some M3 — not a single universal standard.
Eurorack is a strong known case with two competing metric standards (M2.5 for Vector rails, M3 for Schroff/DIN-style and 3U threaded rails); mixing rail types requires matching screw/nut thread.

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.

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The same screw also fits

Devices whose records share a thread with MGN9 linear rail, closest length match first.

NEMA 17 stepper motor faceplate also M3 × 6–8 mm
MGN12 linear rail also M3 × 8 mm
2020 extrusion T-nuts (light duty) also M3 × 6–8 mm
NEMA 17 stepper motor face also M3 × 6–8 mm
OpenBuilds gantry plate brackets also M3 × 6–8 mm
VEX / Actobotics channel and gussets also M3 × 8 mm
Arduino shield stacking standoffs also M3 × 8 mm
Bambu Lab X1/P1/AMS spare screw kit also M3 × 6–8 mm

Questions about MGN9 linear rail screws

What size screw does MGN9 linear rail use?: M3 × 6–8 mm for countersunk bolts fixing the small rail to the frame.
How long are the screws in MGN9 linear rail?: The records range from 6 to 8 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 MGN9 linear rail?: 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 MGN9 linear rail?: TechSpareWarehouse (our own store) lists M3 x 6mm and M3 x 8mm, which match lengths in the records above.

Heads up: shipping delay