Shield Sights optic-ready / dovetail red dot mounts screw size
M3 / M4 · length not stated in the sources
Shield Sights optic-ready / dovetail red dot mounts takes M3 and M4 metric screws. None of the sources we found gives an exact length, so measure the original before you order.
There are 2 separate fitment records for it, including optic-to-mount fixing screw, torque 0.8 Nm (M3) and mount-to-firearm fixing screw, torque 2 Nm (M4).
2 of the 2 records are marked confirmed, drawn from 1 source (shieldsights.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.
Shield Sights optic-ready / dovetail red dot mounts screw specifications
One row per fitment record. Head, drive and torque are shown only where the source states them; pitch is the ISO coarse pitch for the thread.
| Thread | Length | Pitch | Head | Drive | Torque | Where it goes | Status |
|---|---|---|---|---|---|---|---|
| M3 | not stated | 0.5 mm | not stated | not stated | 0.8 Nm | optic-to-mount fixing screw, torque 0.8 Nm | Confirmed |
| M4 | not stated | 0.7 mm | not stated | not stated | 2 Nm | mount-to-firearm fixing screw, torque 2 Nm | Confirmed |
Fitment records and sources
optic-to-mount fixing screw, torque 0.8 Nm
pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10
mount-to-firearm fixing screw, torque 2 Nm
pitch 0.7 mm · tap 3.3 mm · clearance 4.5 mm · PH2 / Torx T20
How to check the screw before you buy
- Do not confuse metric mounting screws with the 1/4-20 or 3/8-16 tripod threads that cameras and clamps also carry.
- Diameter: across the threads an M3 screw measures about 3 mm with calipers (usually a hair under). This device also uses M4, so measure each screw rather than assuming they match.
- 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.
Common mix-ups with M3 / M4
- Many gas-detector and sensor manuals only give a torque spec (e.g. '0.5 N·m max') without repeating the thread size at every mention — the explicit M3 callout is usually only in the accessories/spare-parts table, not the main installation steps.
- Terminal-block clamp screws have manufacturer-specific torque values — over-tightening cracks the block or crushes the wire.
- Festo sensor brackets are named after the sensor interface (DASP-M4-...), but the bracket's own fixing screws are often a different size (M5/M6/M8).
- Display mounts mix systems: the screen side is metric M4/M6, but the wall side of many mounts uses imperial wood screws such as #14 x 2.5in.
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Devices whose records share a thread with Shield Sights optic-ready / dovetail red dot mounts, closest length match first.
- Telescope metric thumb screw for telescope parts also M3
- Thorlabs KMS/M compact kinematic mirror mount also M4
- ATC (Advanced Transportation Controller) traffic signal cabinet standard also M4
- Celestron C8 Schmidt-Cassegrain OTA secondary mirror collimation screws also M3
- Arca-style quick-release plate also M3
- Celestron EdgeHD 11" OTA secondary mirror collimation screws also M3
- Basler ace 2 / racer 2 S camera body mounting screws also M3
- Sig Sauer ROMEO1 Pro mounting screw also M4
Questions about Shield Sights optic-ready / dovetail red dot mounts screws
- What size screw does Shield Sights optic-ready / dovetail red dot mounts use?
- M3 for optic-to-mount fixing screw, torque 0.8 Nm; M4 for mount-to-firearm fixing screw, torque 2 Nm.
- How long are the screws in Shield Sights optic-ready / dovetail red dot mounts?
- 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 Shield Sights optic-ready / dovetail red dot mounts?
- 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.
- How tight should the M3 screw on Shield Sights optic-ready / dovetail red dot mounts be?
- The source gives 0.8 Nm for optic-to-mount fixing screw, torque 0.8 Nm.