LEGO Technic-compatible threaded metal axle screw size
M4 · 45 mm long
LEGO Technic-compatible threaded metal axle takes M4 metric screws, 45 mm long.
The record covers aftermarket metal Technic-compatible axle explicitly sold as '45L THREADED M5 Metal Axle' -- note this specific listing is M5, included here for cross-reference to the M4/M5 family used in metal Technic-style axle replacements.
This entry is marked confirmed and comes from metal-technic-parts.com.
An M4 screw is 4 mm in diameter with a 0.7 mm pitch, tapped with a 3.3 mm drill; imperial look-alike: #8-32 (4.17 mm) — the standard US PC/rack screw, close but not the same.
LEGO Technic-compatible threaded metal axle 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 |
|---|---|---|---|---|---|---|
| M4 | 45 mm | 0.7 mm | not stated | not stated | Aftermarket metal Technic-compatible axle explicitly sold as '45L THREADED M5 Metal Axle' -- note this specific listing is M5, included here for cross-reference to the M4/M5 family used in metal Technic-style axle replacements | Confirmed |
Fitment records and sources
Aftermarket metal Technic-compatible axle explicitly sold as '45L THREADED M5 Metal Axle' -- note this specific listing is M5, included here for cross-reference to the M4/M5 family used in metal Technic-style axle replacements
pitch 0.7 mm · tap 3.3 mm · clearance 4.5 mm · PH2 / Torx T20
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 M4 screw measures about 4 mm with calipers (usually a hair under). If yours measures noticeably more or less, it is a different thread.
- Pitch: 0.7 mm from one thread crest to the next (14.29 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 record states 45 mm. Going longer risks bottoming out or touching parts behind the hole; going shorter loses thread engagement.
- Driver: the source does not name the drive. Standard M4 heads take PH2 for Phillips and T20 for Torx, and a 3 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 M4 is about 2.0-3.0 N·m into metal threads and 0.8-1.4 N·m into plastic bosses; snug it up and stop.
Common mix-ups with M4
- Standard injection-molded LEGO Technic axles/pins are friction-fit, not threaded; only specialty metal aftermarket axle replacements use real ISO metric threads (M4/M5), and these are not official LEGO parts.
- 'Semus' in the Kern manual is a brand/head-style qualifier on the screw, not a separate thread designation — the metric callout is still plainly M4.
More in 3D Printing, CNC & Robotics
The same screw also fits
Devices whose records share a thread with LEGO Technic-compatible threaded metal axle, closest length match first.
- Wurth Elektronik WA-SSTIE steel spacer stud also M4 × 45 mm
- Kolm Engines EZ77V4 model aircraft engine also M4 × 45 mm
- Bien-Air Dental Handpieces also M4 × 45 mm
- cab Applicator A3200 print-and-apply labeling system (packaging line hardware) also M4 × 45 mm
- Makeblock cap screw round head hex M4 (catalog part) also M4
- Carbide3D Shapeoko 5 Pro CNC router also M4
- InMoov open-source robot also M4
- Maytronics Dolphin Supreme M4 Robotic Pool/Pond Cleaner also M4
Questions about LEGO Technic-compatible threaded metal axle screws
- What size screw does LEGO Technic-compatible threaded metal axle use?
- M4 × 45 mm for aftermarket metal Technic-compatible axle explicitly sold as '45L THREADED M5 Metal Axle' -- note this specific listing is M5, included here for cross-reference to the M4/M5 family used in metal Technic-style axle replacements.
- How long are the screws in LEGO Technic-compatible threaded metal axle?
- The record gives 45 mm. Measure the original from under the head (overall for a countersunk head) to confirm before ordering.
- What is the thread pitch of an M4 screw?
- 0.7 mm (coarse), which is the standard pitch for M4 machine screws; a 0.5 mm fine pitch exists but is uncommon. The tap drill is 3.3 mm and the normal clearance hole is 4.5 mm.
- What screwdriver do I need for LEGO Technic-compatible threaded metal axle?
- The sources do not name the drive. For M4, Phillips heads normally take PH2 and Torx heads T20; socket heads take a 3 mm hex key.
- Can I use an imperial screw instead of M4?
- No. Imperial look-alike: #8-32 (4.17 mm) — the standard US PC/rack screw, close but not the same. Use a true M4 screw so it does not cross-thread or strip the hole.