Main barrel / eyepiece extension tube holder set screws screw size
M4 · length not stated in the sources
If you are replacing a screw on Main barrel / eyepiece extension tube holder set screws, the thread is M4. None of the sources we found gives an exact length, so measure the original before you order.
The record covers scopeStuff database: 'Main Barrel, eyepiece extension tube holder (2) = M4-.7'.
This entry is marked confirmed and comes from scopestuff.com.
For reference, M4 is 4 mm across the threads at 0.7 mm pitch. The imperial size people confuse it with: #8-32 (4.17 mm) — the standard US PC/rack screw, close but not the same.
Main barrel / eyepiece extension tube holder set screws 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 | not stated | 0.7 mm | not stated | not stated | ScopeStuff database: 'Main Barrel, eyepiece extension tube holder (2) = M4-.7' | Confirmed |
Fitment records and sources
M4confirmed
ScopeStuff database: 'Main Barrel, eyepiece extension tube holder (2) = M4-.7'
pitch 0.7 mm · tap 3.3 mm · clearance 4.5 mm · PH2 / Torx T20
How to check the screw before you buy
- Camera and optics hardware often uses short screws into thin threaded plates, so check engagement before tightening fully.
- 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.
- 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
- On sensors, an "M4" or "M12" marking often describes the sensor barrel or connector thread, not the mounting screw - check which one the datasheet means.
- M4 and 6-32 UNC share a nominal diameter with different pitch — a classic cross-thread in US-market kits.
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Devices whose records share a thread with Main barrel / eyepiece extension tube holder set screws, closest length match first.
- Thorlabs KM200CP/M kinematic mount for 2-inch optics also M4
- DJI RS 5 / RS 4 / RS 3 / RSC 2 gimbal camera mount also M4
- Thorlabs FW103/M motorized filter wheel also M4
- DJI RS series gimbals (RS 5, RS4 Pro, RS4, RS3 Mini/Pro/3, RS2, RSC2) also M4
- Celestron collimation screws, C8/C9.25/C11 SCT optical tubes also M4
- Newport M-SP-4 optical post, 101.6mm height, 12.7mm diameter also M4
- SIG SAUER ROMEO-RS reflex sight, mounting to SIG Pro-cut slides / P365 slides with M4 mount holes also M4
- Celestron NexStar 8 eyepiece holder set screws also M4
Questions about Main barrel / eyepiece extension tube holder set screws screws
- What size screw does Main barrel / eyepiece extension tube holder set screws use?
- M4 for scopeStuff database: 'Main Barrel, eyepiece extension tube holder (2) = M4-.7'.
- How long are the screws in Main barrel / eyepiece extension tube holder set screws?
- 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 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 Main barrel / eyepiece extension tube holder set screws?
- 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.