RC glow/gas engine mount bolts screw size
M3 · length not stated in the sources
The screws used on RC glow/gas engine mount bolts are M3. None of the sources we found gives an exact length, so measure the original before you order.
Where it is used: firewall and beam mount bolts, M3-M4 depending on engine.
This entry is marked reported and comes from forums.modelflying.co.uk.
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.
RC glow/gas engine mount bolts 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 | not stated | Firewall and beam mount bolts, M3-M4 depending on engine | Reported |
Fitment records and sources
Firewall and beam mount bolts, M3-M4 depending on engine
pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10
How to check the screw before you buy
- Vibration loosens small screws on drones and RC models, so builders commonly add a drop of medium (blue) threadlocker on metal-to-metal joints — never on plastic.
- 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 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
- Thorlabs' 16mm cage system standard plates use dual 4-40 (UNC) and M3 taps on the same plate (e.g., SP01), so metric and imperial fasteners are both valid depending on the region/kit purchased.
- M3 (3.0mm, 0.5mm pitch) is not #6-32 UNC (~3.5mm) — they look identical and cross-thread, the single most common PC-building mistake.
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Devices whose records share a thread with RC glow/gas engine mount bolts, closest length match first.
- FPV flight controller stack (generic kit) also M3
- GetFPV anti-vibration FC standoff 7mm also M3
- FPV flight-controller / ESC stacks also M3
- E-flite Gee Bee R-2 1.0m wing securing screws also M3
- 3D-printed FPV stack mounts and spacers also M3
- VXB flight controller anti-vibration standoffs also M3
- FPV carbon frame arms and standoffs also M3
- Futaba standard servo horn screw also M3
Questions about RC glow/gas engine mount bolts screws
- What size screw does RC glow/gas engine mount bolts use?
- M3 for firewall and beam mount bolts, M3-M4 depending on engine.
- How long are the screws in RC glow/gas engine mount bolts?
- 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 RC glow/gas engine mount bolts?
- 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.