Celestron 1.25in Ultima Barlow (1999) screw size
M3 · length not stated in the sources
Our records put Celestron 1.25in Ultima Barlow (1999) on M3 screws. None of the sources we found gives an exact length, so measure the original before you order.
The record covers locking/retaining screw, M3-0.5.
This entry is marked confirmed and comes from scopestuff.com.
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.
Celestron 1.25in Ultima Barlow (1999) 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 | locking/retaining screw, M3-0.5 | Confirmed |
Fitment records and sources
M3confirmed
locking/retaining screw, M3-0.5
pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10
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). 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
- Telescope thumbscrews are sold in a wide non-metric legacy range too (1/4-20, 8-32, 10-32 on many Meade/Celestron mounts), so metric M3/M4 fitment applies mainly to newer/international accessory ecosystems (SkyWatcher, generic 1.25" accessories) and should not be assumed universal.
- Drill chuck retaining screws are commonly LEFT-HAND thread (e.g. M6 x 1.0 LH) — turn clockwise to remove.
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Devices whose records share a thread with Celestron 1.25in Ultima Barlow (1999), closest length match first.
- Telescope accessory thumb screws also M3
- Gimbal / quick-release plate clamp also M3
- Celestron collimation screws, C5/C6/C8 SCT optical tubes also M3
- Wooden Camera 153250 SSD Guard (RED EPIC) also M3
- Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal also M3
- Celestron 1.25" 2x Ultima Barlow 'shorty' set screw also M3
- Holosun SCS mounting screw (Walther PDP) also M3
- Wooden Camera 153200 SSD Guard (RED SCARLET) also M3
Questions about Celestron 1.25in Ultima Barlow (1999) screws
- What size screw does Celestron 1.25in Ultima Barlow (1999) use?
- M3 for locking/retaining screw, M3-0.5.
- How long are the screws in Celestron 1.25in Ultima Barlow (1999)?
- 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 Celestron 1.25in Ultima Barlow (1999)?
- 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.