Celestron 1.25" 2x Ultima Barlow 'shorty' set screw screw size
M3 · length not stated in the sources
The screws used on Celestron 1.25" 2x Ultima Barlow 'shorty' set screw are M3. None of the sources we found gives an exact length, so measure the original before you order.
The record covers screw-size database lists this Barlow's thumb/set screw explicitly as M3-0.5.
Head and drive, as the source states them: set screw (headless) head.
This entry is marked confirmed and comes from scopestuff.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.
Celestron 1.25" 2x Ultima Barlow 'shorty' set screw 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 | Set screw (headless) | not stated | Screw-size database lists this Barlow's thumb/set screw explicitly as M3-0.5 | Confirmed |
Fitment records and sources
Screw-size database lists this Barlow's thumb/set screw explicitly as 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
- Camera and optics hardware often uses short screws into thin threaded plates, so check engagement before tightening fully.
- 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: for set screw (headless) screws, measure from under the head to the tip (countersunk heads are the exception: they 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.
- Suunto dive computer service manuals reference strap pins and battery compartment springs but do not explicitly cite a metric screw thread size in the sections reviewed; do not infer M2/M2.5 fitment for Suunto dive computer straps without direct confirmation.
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Devices whose records share a thread with Celestron 1.25" 2x Ultima Barlow 'shorty' set screw, closest length match first.
- Holosun SCS mounting screw (Walther PDP) also M3
- Wooden Camera 153200 SSD Guard (RED SCARLET) also M3
- Meade LX200 Barlow / eyepiece retaining screw also M3
- Celestron C14 Schmidt-Cassegrain OTA secondary mirror collimation screws also M3
- Celestron C6 Schmidt-Cassegrain OTA secondary mirror collimation screws also M3
- Airsoft red dot sight mounting screw set (Laylax/Quintes Sence) also M3
- Slim optical drives (9.5 / 12.7mm) also M3
- Basler ace L USB 3.0 also M3
Questions about Celestron 1.25" 2x Ultima Barlow 'shorty' set screw screws
- What size screw does Celestron 1.25" 2x Ultima Barlow 'shorty' set screw use?
- M3 for screw-size database lists this Barlow's thumb/set screw explicitly as M3-0.5.
- How long are the screws in Celestron 1.25" 2x Ultima Barlow 'shorty' set screw?
- 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 1.25" 2x Ultima Barlow 'shorty' set screw?
- 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.