What size screw does GCX Barcode Scanner Adapter mounting kit use?

M3 × 6–8 mm for installation guide bill of materials lists "2 M3 x 6 PHMS" and "4 M3 x 8 PHMS" as included mounting screws for the barcode scanner adapter bracket; M4 × 20 mm for installation guide bill of materials lists "4 M4 x 20 FHMS" flat-head machine screws as part of the scanner adapter mounting hardware kit.

How long are the screws in GCX Barcode Scanner Adapter mounting kit?

The records range from 6 to 20 mm depending on the position, so match each screw to its own hole.

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 GCX Barcode Scanner Adapter mounting kit?

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.

Where can I buy replacement screws for GCX Barcode Scanner Adapter mounting kit?

TechSpareWarehouse (our own store) lists M3 x 6mm and M3 x 8mm, which match lengths in the records above.

GCX Barcode Scanner Adapter mounting kit screw size

M3 / M4 · 6 to 20 mm long

If you are replacing a screw on GCX Barcode Scanner Adapter mounting kit, the thread is M3 and M4 in lengths from 6 to 20 mm.

There are 2 separate fitment records for it, including installation guide bill of materials lists "2 M3 x 6 PHMS" and "4 M3 x 8 PHMS" as included (M3) and installation guide bill of materials lists "4 M4 x 20 FHMS" flat-head machine screws as pa (M4).

Head and drive, as the sources state them: flat / countersunk head.

2 of the 2 records are marked confirmed, drawn from 1 source (gcx.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.

GCX Barcode Scanner Adapter mounting kit 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	6–8 mm	0.5 mm	not stated	not stated	Installation guide bill of materials lists "2 M3 x 6 PHMS" and "4 M3 x 8 PHMS" as included mounting screws for the barcode scanner adapter bracket	Confirmed
M4	20 mm	0.7 mm	Flat / countersunk	not stated	Installation guide bill of materials lists "4 M4 x 20 FHMS" flat-head machine screws as part of the scanner adapter mounting hardware kit	Confirmed

Fitment records and sources

M36-8mmconfirmed

Installation guide bill of materials lists "2 M3 x 6 PHMS" and "4 M3 x 8 PHMS" as included mounting screws for the barcode scanner adapter bracket

pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10

Source

M420mmconfirmed

Installation guide bill of materials lists "4 M4 x 20 FHMS" flat-head machine screws as part of the scanner adapter mounting hardware kit

pitch 0.7 mm · tap 3.3 mm · clearance 4.5 mm · PH2 / Torx T20

Source

How to check the screw before you buy

Board standoffs and enclosure bosses set the usable length: the screw should clamp the board without bottoming in the standoff.
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: the source describes a countersunk (flat) head, and those are measured overall, from the top of the head to the tip.
The records span 6–20 mm, which means different positions take different lengths — match each hole to its own screw.
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 / M4

Camera and tripod mounting threads themselves are imperial 1/4in-20 or 3/8in-16 — the metric M2-M4 screws in rig kits are only for the accessory hardware, not the tripod mount.
Label printer parts lists write M3*6 with an asterisk; that is still a true ISO M3 x 6mm machine screw.
Not all telescope/finder hardware is metric — Celestron Edge/NexStar SE finder-shoe and dovetail screws are reported as 8/32 (imperial UNC), so metric M4/M5 fitments cannot be assumed across all Celestron products; must check per accessory/vintage.
Most HVAC chassis hardware in US-market units is imperial; metric shows up mainly on European-made components.

Pitch gauge · Screw size finder · Torque guide

Buy these screws at TechSpare Warehouse

In stock and shipped from South Carolina. Our black screws are Phillips wafer head (low profile); match the head style and length to the original before you order.

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The same screw also fits

Devices whose records share a thread with GCX Barcode Scanner Adapter mounting kit, closest length match first.

Rack blanking panels and front handles also M3 × 6–8 mm
cab Applicator A3200 print-and-apply labeling system (packaging line hardware) also M3 × 6–8 mm
Allen & Heath ZED mixer rack ear kit AP7956 also M3 × 8 mm
Linksys WRT54G2 router also M3 × 8 mm
Takachi EM-series enclosure PCB bosses also M3 × 6 mm
ICY DOCK MB344SP FLEX-FIT Quattro 5.25" bay enclosure also M3 × 6 mm
Car interior trim and dash panel screws also M3 × 8 mm
Linksys E7350 router also M3 × 8 mm

Questions about GCX Barcode Scanner Adapter mounting kit screws

What size screw does GCX Barcode Scanner Adapter mounting kit use?: M3 × 6–8 mm for installation guide bill of materials lists "2 M3 x 6 PHMS" and "4 M3 x 8 PHMS" as included mounting screws for the barcode scanner adapter bracket; M4 × 20 mm for installation guide bill of materials lists "4 M4 x 20 FHMS" flat-head machine screws as part of the scanner adapter mounting hardware kit.
How long are the screws in GCX Barcode Scanner Adapter mounting kit?: The records range from 6 to 20 mm depending on the position, so match each screw to its own hole.
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 GCX Barcode Scanner Adapter mounting kit?: 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.
Where can I buy replacement screws for GCX Barcode Scanner Adapter mounting kit?: TechSpareWarehouse (our own store) lists M3 x 6mm and M3 x 8mm, which match lengths in the records above.

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