M2 Screw Dimensions: Complete Size Chart, Head Types & Specs

Quick answer: An M2 screw has a 2 mm nominal outer diameter, a standard thread pitch of 0.4 mm, and is available in lengths ranging from 2 mm to 50 mm. Head styles include socket cap (DIN 912), pan head, countersunk, flat head, and button head — each with distinct dimensional envelopes defined by ISO 4762 and related standards.

You’re mid-build on a compact electronics enclosure or a robot servo bracket, and you reach for what looks like a standard screw. It’s labeled “M2” — but is that the thread diameter, the head diameter, or some other spec entirely? And why does your M2 SSD mounting screw look nothing like the M2 fasteners in your parts drawer?

This guide answers both questions and goes further: exact m2 screw dimensions in mm and inches, full head-type charts, drill and tapping hole sizes, torque values by material, and a direct comparison against M2.5 and M3. By the end, you’ll be able to specify, source, and install M2 screws without second-guessing the datasheet.

What Are M2 Screw Dimensions?

M2 screws follow the ISO metric fastener system, where the “M” prefix denotes a metric thread and the number is the nominal outer (major) diameter in millimeters. So an M2 screw has a 2 mm nominal diameter — though due to manufacturing tolerances allowed by ISO 286 and DIN standards, the actual measured diameter typically falls between 1.9 mm and 2.0 mm.

Per ISO metric screw thread specifications, the full thread designation combines the diameter with the pitch: M2 × 0.4 means 2 mm diameter, 0.4 mm pitch. That 0.4 mm pitch is the coarse standard — the distance from one thread crest to the next. Fine-pitch variants (M2 × 0.25) exist for high-precision or vibration-prone assemblies, but coarse pitch covers 95% of everyday applications.

Nominal Diameter, Thread Pitch & Length Explained

The three numbers that fully define an M2 screw are:

1. Diameter (M2) — 2 mm nominal outer thread diameter
2. Pitch (0.4 mm) — axial distance between adjacent thread crests
3. Length — shank length measured from under the head (for socket cap and pan head styles); for countersunk screws, length is measured from the top of the head

A screw labeled M2 × 8 therefore has a 2 mm diameter, standard 0.4 mm pitch, and an 8 mm shank. That “8 mm” does not include the head on a socket cap or pan head screw — a critical point when calculating standoff depth.

M2 thread geometry by the numbers:

M2 Screw Dimensions in mm vs Inches

Metric screws dominate electronics and precision engineering globally, but North American shops and spec sheets often need inch equivalents. Converting m2 screw dimensions is straightforward — 1 mm = 0.03937 inches.

In North American hardware stores, M2 screws are sometimes stocked alongside #1-72 UNC screws (1.854 mm, 0.073″) and #0-80 UNF (1.524 mm, 0.060″). Neither is a true substitute for M2 — the pitch angles don’t match, and the diameters diverge enough to risk thread stripping in plastic housings.

M2 Screw Head Types and Their Dimensions

The head is where m2 screw dimensions get genuinely complicated. Same M2 × 8 designation can appear in six or more head profiles, each with a different head diameter, height, and drive recess. Specifying “M2 screw” without the head type is like ordering “a coffee” without specifying size or roast.

Socket Head Cap Screws (DIN 912 / ISO 4762)

The socket head cap screw — sometimes called a hex socket or Allen head — is the most widely stocked M2 variant in engineering and electronics. The cylindrical head with a hexagonal internal drive gives more wrenching torque than a cross-drive head of equivalent size, which matters when threading into aluminum or stainless-steel tapped holes.

Key m2 screw dimensions for DIN 912 socket head cap:

The 1.5 mm hex key is standard — any precision screwdriver set for electronics work should include it.

Pan Head, Countersunk & Flat Head

Pan head screws (DIN 7985 with Phillips drive, or ISO 14583 with Torx) have a low, flat-topped dome with a larger bearing surface than socket cap screws. They’re the default for attaching PCBs to standoffs and for sheet-metal enclosures where the protruding head is acceptable.

Countersunk screws (DIN 965 for cross-drive, DIN 7991 for hex socket) are designed to sit flush with the mating surface. The head has a 90° countersink angle (some specialty variants use 82°). Critical detail: the length of a countersunk screw is measured from the top of the head, not under it.

Flat head (also called “flat countersunk”) is essentially the same geometry as countersunk — the terms are often used interchangeably for M2 sizes.

Cheese Head, Button Head & Specialty Types

Button head screws (ISO 7380) have a low-profile dome — lower than pan head, higher than countersunk — with a hex socket drive. They’re popular in robotics and RC hardware where head height clearance is tight but a flush countersink isn’t required.

Cheese head screws (DIN 84) feature a straight cylindrical head slightly larger in diameter than the socket cap, with a slotted drive. They’re less common in modern precision work but still appear in vintage electronics and calibration equipment.

Captive screws and thread-forming variants (e.g., PT screws for plastic) exist in M2 diameters as well. Thread-forming M2 screws cut their own path in pre-drilled plastic holes — no tapping required — but they require a larger pilot hole than a standard tapped M2.

Full M2 Screw Dimensions Chart

Standard Length Series

M2 screws are manufactured in preferred length increments. Not every length is available in every head style or material, so confirming stock before specifying an unusual length saves time.

For electronics work, the most-stocked lengths are 3 mm, 4 mm, 5 mm, and 6 mm. Laptop manufacturers lean heavily on M2 × 3 and M2 × 4 for PCB and hinge mounting; drone frames often use M2 × 5 and M2 × 6.

M2 Screw Head Diameter by Drive Type

One of the most practical m2 screw dimensions to keep in mind is the minimum counterbore diameter — the hole diameter needed to fully recess the head. This is roughly the head diameter plus 0.1–0.2 mm clearance.

Drill Hole Size & Torque Specifications for M2 Screws

Getting the hole size wrong is the single most common installation error with M2 screws. Too small and you split the material or snap the fastener; too large and threads strip under torque.

Correct Clearance and Tapping Drill Sizes

There are two distinct hole situations:

Clearance hole — a through-hole that the screw passes through freely, used when threading into a nut or the mating part provides the thread engagement. For M2, the standard clearance hole is 2.2 mm (close fit) or 2.4 mm (medium/free fit).

Tapping hole (pilot hole) — a blind or through-hole that is then tapped with an M2 × 0.4 tap to create internal threads. The correct tapping drill is 1.6 mm for standard materials.

For PCB-to-standoff applications, a 2.2 mm clearance hole is standard — it fits M2 screws with minimal board shift while leaving room for the 3.8 mm head to seat flat.

Torque Values by Material

M2 screws are small enough that it’s easy to overtorque them, especially in aluminum and plastic. The numbers below are conservative practical targets — not absolute limits from the ASME Fastener Standards database, which gives proof loads under controlled lab conditions.

In practice, most electronics assembly uses finger-tight plus a quarter to half turn rather than a calibrated torque driver — and that’s usually fine for non-structural, low-vibration applications. Where vibration is a factor (motors, fans, chassis), add a thread-locking compound or a nylon-insert nut.

M2 Screw Applications by Industry

Electronics, Laptops & Mobile Devices

M2 screws are the default fastener for consumer electronics. Open any laptop manufactured in the last decade and you’ll find M2 × 3 or M2 × 4 socket cap screws holding the bottom cover, M2 × 4 or M2 × 5 for heatsink retention, and M2 × 2.5 or M2 × 3 for PCB-to-chassis mounts. Smartphone camera modules and OLED panels in premium devices use sub-M2 metric screws (M1.6, M1.4), but M2 is the smallest practical size for anything field-serviceable.

Cameras — especially interchangeable-lens bodies — rely on M2 screws for sensor mount brackets, shutter unit retention, and internal PCB attachment. The 2 mm diameter is small enough to fit within tight tolerances yet strong enough to hold alignment-critical components over tens of thousands of actuations.

PC Building: The M.2 SSD Screw Confusion

Here’s the most searched confusion point in this entire topic: M.2 SSD screws are not the same as M2 metric screws — they share only the “M2” letter combination.

An M.2 SSD is a form factor (22 mm wide, variable length: 2230, 2242, 2260, 2280). The tiny screw that retains the drive to the motherboard standoff is genuinely an M2 metric screw — but specifically a flat-head M2 × 2.5 mm or M2 × 3 mm with a Phillips or cross-recess drive. As confirmed by the r/buildapc community reference, the standard M.2 retention screw is a flat-head M2.0 × 2.5 mm.

What confuses people: the “M.2” in “M.2 SSD” refers to the connector standard (formerly called NGFF), not the thread size. The thread size happening to also be M2 is coincidence. Most motherboard manufacturers include one or two M2 × 2.5 screws in the accessory bag, but they’re easy to lose — and most hardware stores don’t stock them because the 2.5 mm length is non-standard.

If you lost your M.2 SSD screw: look for an M2 × 3 flat countersunk screw (slightly longer but usually works), or order an M2 × 2.5 flat head online. Do not substitute an M2.5 screw — the 2.5 mm diameter will not thread into the M2 standoff.

Precision Instruments & Robotics

Beyond consumer electronics, m2 screw dimensions suit any application where fastener weight and bulk matter. Hobbyist and commercial quadcopters use M2 × 5 and M2 × 6 socket cap screws to mount motor bell housings to arms; the low head height of button-head M2s is preferred when clearance to rotating components is tight.

Medical device prototypes, optical alignment fixtures, and watch-mechanism repairs all rely on M2 or sub-M2 fasteners. Titanium M2 screws are specified in weight-critical aerospace and implant applications — at 2 mm diameter, the weight difference between a steel and titanium screw is fractions of a gram, but it adds up across hundreds of fasteners.

M2 vs M2.5 vs M3: When to Use Each

The M2, M2.5, and M3 are the three smallest metric thread sizes that see regular use. Understanding when to substitute — and when not to — prevents stripped threads and structural failures.

Dimensional Comparison

Substitution Rules & Common Mistakes

M2 → M2.5: Only possible if you re-drill the tapped hole to 2.05 mm and re-tap it. The thread pitches are different (0.40 vs 0.45 mm), so an M2 screw cannot engage an M2.5 thread. This is the mistake that damages M.2 SSD standoffs when someone inserts an M2.5 screw.

M2 → M3: A 50% diameter increase — the clearance hole must be enlarged to 3.2 mm. This changes the structural footprint significantly and is rarely practical in existing electronics assemblies.

When to specify M3 over M2: Any mechanical joint seeing dynamic loads, vibration, or repeated assembly/disassembly cycles. M2 aluminum-thread joints in fan mounts have a notoriously short service life under vibration; M3 with a thread insert holds significantly longer.

When M2 is the right choice: Any application where board or housing real estate under 4 mm head diameter is required, or where screw weight is a design constraint. M2 is also the natural choice when mating to OEM standoffs (laptops, cameras, telecom equipment) that were designed for M2.

Material Options for M2 Screws

Stainless Steel, Titanium & Specialty Alloys

The most common M2 materials, ranked by frequency of use in engineering and electronics:

1. A2 stainless steel (304) — corrosion-resistant, non-magnetic (important for RF and sensor applications), good general mechanical properties. The default for consumer electronics and outdoor equipment.
2. Low-carbon steel (black oxide or zinc-plated) — higher tensile strength per dollar than stainless, but requires corrosion protection. Common in automotive and industrial OEM assemblies.
3. Titanium (Grade 5, Ti-6Al-4V) — roughly 45% lighter than steel M2 screws, excellent corrosion resistance, near-zero magnetic signature. Preferred in aerospace assemblies and high-end cycling/drone components where every gram counts.
4. Brass — naturally corrosion-resistant, machinable, excellent for electrical-conductivity grounding studs. Softer than steel — torque limit is roughly 60–70% of equivalent steel M2.
5. Aluminum — even lighter than titanium at M2 scale; structurally marginal for torque-bearing joints. Used mostly as a sacrificial or alignment fastener.
6. Nylon / PEEK — non-conductive, chemical-resistant; used in PCB isolation mounts and chemical-process equipment. Torque limit is very low — tighten by feel only.

The Engineering Toolbox’s fastener materials comparison provides detailed tensile and yield strength data for steel grades. For M2 in 8.8 grade steel, minimum tensile strength is 800 N/mm² — roughly 2,500 N proof load capacity for the thread form.

Choosing by Environment

FAQ

What is the exact diameter of an M2 screw?
An M2 screw has a 2 mm nominal outer (major) thread diameter. Due to ISO manufacturing tolerances, the actual measured diameter is typically 1.90–2.00 mm. The “M2” designation in ISO metric standards means the nominal thread outer diameter is 2 millimeters — not to be confused with the smaller pitch diameter (1.740 mm) or the minor (root) diameter (1.567 mm).

What thread pitch does an M2 screw use?
The standard coarse pitch for M2 screws is 0.4 mm — meaning each thread crest is 0.4 mm apart along the axis. A fine-pitch variant (M2 × 0.25) is available for high-precision applications requiring finer thread engagement or reduced backlash. If you’re ordering M2 screws without specifying pitch, you’ll receive the coarse 0.4 mm standard.

What drill bit size do I need for an M2 tapping hole?
Use a 1.6 mm drill bit for a standard M2 × 0.4 tapping hole in aluminum, steel, or brass. For harder materials like stainless steel, some machinists prefer 1.65 mm to reduce tap breakage. For a clearance (pass-through) hole, drill 2.2 mm for a close fit or 2.4 mm for a medium fit.

Is an M2 screw the same as the screw that holds an M.2 SSD?
Yes and no. The physical fastener used to retain an M.2 SSD to a motherboard standoff is an M2 metric screw (2 mm diameter) — typically a flat-head M2 × 2.5 mm or M2 × 3 mm. The “M.2” in M.2 SSD refers to the storage form-factor standard, not the fastener. The coincidence of names is a perpetual source of confusion in the PC building community. Bottom line: the SSD retention screw is a genuine M2 fastener, but a specific flat-head variety.

What is the head size of an M2 socket cap screw?
For a standard M2 socket cap screw (DIN 912 / ISO 4762), the head diameter is 3.8 mm and the head height is 2.0 mm. The internal hex drive takes a 1.5 mm hex key. The minimum counterbore diameter to recess this head flush is 4.0 mm with a 2.1 mm depth.

What is the torque specification for an M2 screw?
There is no single torque value — it depends on the mating material and screw grade. Practical guidelines: 0.08–0.12 N·m into plastic (PCBs, nylon standoffs); 0.15–0.22 N·m into aluminum; 0.25–0.40 N·m into steel. Overtorquing aluminum threads is the most common cause of M2 joint failure — the thin thread wall strips easily. When in doubt, finger-tight plus a quarter turn is a safe practical limit for electronics work.

What sizes are available for M2 screws?
Standard M2 screw lengths run from 2 mm to 50 mm in preferred increments (2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 25, 30, 40, 50 mm). Not all lengths are stocked in every head style — socket cap screws are available in the full range; specialty heads (button, countersunk) typically go to 20–25 mm. Custom lengths to 100 mm are available to order from precision fastener suppliers.

Conclusion

M2 screw dimensions are deceptively simple on the surface — 2 mm diameter, 0.4 mm pitch — but the practical detail that determines whether your assembly works or strips lies in head type, hole sizing, torque limit, and material choice. The most important numbers to keep handy: 1.6 mm tapping drill, 2.2 mm clearance hole, 3.8 mm head diameter for socket cap and pan head styles, and a 1.5 mm hex key to drive them.

The M.2 SSD confusion is real and worth remembering: the retention screw is a genuine M2 flat-head × 2.5 mm, but the “M.2” label on your SSD slot is about the connector standard, not the thread. For everything else — robot frames, laptop teardowns, camera servicing, or precision instrument assembly — the tables in this guide give you everything you need to specify m2 screw dimensions confidently without hunting through six different DIN standards PDFs. Pick the right head type for your clearance requirement, drill the correct hole size, and don’t overtorque aluminum.