What size screw does ASUS Chromebox 4 (CN66) use?

M2 × 2.5–4 mm for service guide lists M2 x 2.5, M2 x 3 and M2 x 4 screws for boards and brackets; M2.5 × 4–6 mm for M2.5 x 4 and M2.5 x 6 screws used in chassis disassembly.

How long are the screws in ASUS Chromebox 4 (CN66)?

The records range from 2.5 to 6 mm depending on the position, so match each screw to its own hole.

What is the thread pitch of an M2 screw?

0.4 mm (coarse), which is the standard pitch for M2 machine screws; a 0.25 mm fine pitch exists but is uncommon. The tap drill is 1.6 mm and the normal clearance hole is 2.4 mm.

What screwdriver do I need for ASUS Chromebox 4 (CN66)?

The sources do not name the drive. For M2, Phillips heads normally take PH0 and Torx heads T6; socket heads take a 1.5 mm hex key.

Can I use an imperial screw instead of M2?

No. Imperial look-alike: #2-56 UNC (2.18 mm) is close but not interchangeable. Use a true M2 screw so it does not cross-thread or strip the hole.

Where can I buy replacement screws for ASUS Chromebox 4 (CN66)?

TechSpareWarehouse (our own store) lists M2 x 2.5mm, M2 x 3mm and M2 x 4mm, which match lengths in the records above.

ASUS Chromebox 4 (CN66) screw size

M2 / M2.5 · 2.5 to 6 mm long

The screws used on ASUS Chromebox 4 (CN66) are M2 and M2.5 in lengths from 2.5 to 6 mm.

There are 2 separate fitment records for it, including service guide lists M2 x 2.5, M2 x 3 and M2 x 4 screws for boards and brackets (M2) and M2.5 x 4 and M2.5 x 6 screws used in chassis disassembly (M2.5).

2 of the 2 records are marked confirmed, drawn from 1 source (dlcdnets.asus.com).

An M2 screw is 2 mm in diameter with a 0.4 mm pitch, tapped with a 1.6 mm drill; imperial look-alike: #2-56 UNC (2.18 mm) is close but not interchangeable.

ASUS Chromebox 4 (CN66) 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
M2	2.5–4 mm	0.4 mm	not stated	not stated	Service guide lists M2 x 2.5, M2 x 3 and M2 x 4 screws for boards and brackets	Confirmed
M2.5	4–6 mm	0.45 mm	not stated	not stated	M2.5 x 4 and M2.5 x 6 screws used in chassis disassembly	Confirmed

Fitment records and sources

M22.5-4mmconfirmed

Service guide lists M2 x 2.5, M2 x 3 and M2 x 4 screws for boards and brackets

pitch 0.4 mm · tap 1.6 mm · clearance 2.4 mm · PH0 / Torx T6

Source

M2.54mm / 6mmconfirmed

M2.5 x 4 and M2.5 x 6 screws used in chassis disassembly

pitch 0.45 mm · tap 2.05 mm · clearance 2.9 mm · PH1 / Torx T8

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 M2 screw measures about 2 mm with calipers (usually a hair under). This device also uses M2.5, so measure each screw rather than assuming they match.
Pitch: 0.4 mm from one thread crest to the next (25 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.
The records span 2.5–6 mm, which means different positions take different lengths — match each hole to its own screw.
Driver: the source does not name the drive. Standard M2 heads take PH0 for Phillips and T6 for Torx, and a 1.5 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 M2 is about 25-40 N·cm into metal threads and 12-20 N·cm into plastic bosses; snug it up and stop.

Common mix-ups with M2 / M2.5

Xbox Series X internal chassis screws are M3, not M2 (confirmed on iFixit) — a widespread misconception.
M2 CMM stylus threads are a de facto industry standard (Renishaw-originated) rather than a formal ISO CMM spec; do not confuse with M2 electronics screws which have different head/length conventions.
M2.5 pitch is 0.45mm vs M3's 0.5mm and M2's 0.4mm — forcing the wrong one strips plastic bosses instantly.
M2.5 and M3 look the same to the naked eye — you need calipers on the shank to tell them apart.

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 ASUS Chromebox 4 (CN66), closest length match first.

ASUS ZenBook / ROG also M2 × 3 mm
Eurorack module-to-rail mounting screws (Vector/SynthRacks rails) also M2.5 × 6 mm
Keystone metric nylon standoff also M2.5 × 4 mm
Wurth Elektronik WA-SSTIE steel spacer stud also M2.5 × 5–6 mm
Dell XPS 15 9560 also M2 × 2.5–3 mm
Sony PMW-EX1R camcorder - small controls also M2 × 2.5–4 mm
Clear-Com panel PSU module also M2.5 × 5 mm
IPETRONIK M-SENS2 sensor module mounting bracket also M2.5 × 6 mm

Questions about ASUS Chromebox 4 (CN66) screws

What size screw does ASUS Chromebox 4 (CN66) use?: M2 × 2.5–4 mm for service guide lists M2 x 2.5, M2 x 3 and M2 x 4 screws for boards and brackets; M2.5 × 4–6 mm for M2.5 x 4 and M2.5 x 6 screws used in chassis disassembly.
How long are the screws in ASUS Chromebox 4 (CN66)?: The records range from 2.5 to 6 mm depending on the position, so match each screw to its own hole.
What is the thread pitch of an M2 screw?: 0.4 mm (coarse), which is the standard pitch for M2 machine screws; a 0.25 mm fine pitch exists but is uncommon. The tap drill is 1.6 mm and the normal clearance hole is 2.4 mm.
What screwdriver do I need for ASUS Chromebox 4 (CN66)?: The sources do not name the drive. For M2, Phillips heads normally take PH0 and Torx heads T6; socket heads take a 1.5 mm hex key.
Can I use an imperial screw instead of M2?: No. Imperial look-alike: #2-56 UNC (2.18 mm) is close but not interchangeable. Use a true M2 screw so it does not cross-thread or strip the hole.
Where can I buy replacement screws for ASUS Chromebox 4 (CN66)?: TechSpareWarehouse (our own store) lists M2 x 2.5mm, M2 x 3mm and M2 x 4mm, which match lengths in the records above.

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