M4 screw dimensions — 4 mm diameter, 0.7 pitch, head sizes, clearance hole, tap drill
An M4 screw has a 4 mm major diameter and a 0.7 mm coarse pitch. Tables of head dimensions by type, the 4.5 mm clearance hole, the 3.3 mm tap drill and the driver number.
M4 means a screw with a 4 mm major diameter. It is a common size in electronics and machine assembly, and the size with the most items in the JKF catalog (528).
M4 basic dimensions
| Item | Value |
|---|---|
| Nominal diameter | 4 mm |
| Actual major diameter (external thread 6g) | 3.838–3.978 mm |
| Coarse pitch | 0.7 mm |
| Stress area | 8.78 mm² |
| Cross recess number | No. 2 (Phillips bit size chart) |
| Clearance hole | 4.5 mm (ISO 273 medium) |
| Tap drill | 3.3 mm (standard cutting tap) |
An M4 with no pitch stated means the coarse pitch of 0.7.
Length is measured from under the head on pan, truss and binding heads, and from the top of the head to the screw end on countersunk heads. Raised countersunk heads use yet another reference. See how to read a screw designation.
Head dimensions by type (JKF M4 products)
| Head | Head diameter | Head height | Basis |
|---|---|---|---|
| Pan | 7.0 | 2.6 | Based on KS B 1023 |
| Truss | 9.4 | 2.5 | Based on KS B 1023 |
| Binding | 8.3 | 2.5 | Based on KS B 1023 |
| Countersunk | 8.0 | 2.3 | Based on KS B 1023 |
| Raised countersunk | 8.0 | 3.2 | Based on KS B 1023 |
| Small countersunk | 6.0 | 1.4 | In-house standard |
| Pan with washer face | 7.0 | 3.0 | In-house standard |
| Socket head cap screw | 7.0 | 4.0 | Based on KS B 1003 |
Unit: mm, nominal values. Check the product drawing for tolerances. For the pan head, diameter 7 is 0/−0.5 and height 2.6 is ±0.15 (KS B 1023 annex, table A.1).
Most M4 pan heads sold in Korea have these dimensions (diameter 7.0, height 2.6), which come from the KS B 1023 annex.
M4 clearance hole and tap drill
Hole the screw passes through (clearance hole, ISO 273)
| Series | Hole diameter |
|---|---|
| Fine | 4.3 mm |
| Medium | 4.5 mm |
| Coarse | 4.8 mm |
Unless there is a particular reason otherwise, medium 4.5 mm is the usual choice. For a given head or washer diameter, a larger hole means less area clamping the part.
Hole for cutting the thread (tap drill)
For M4 × 0.7 with a standard cutting tap, a 3.3 mm drill is usual. The minor diameter allowed for the finished internal thread (6H) is 3.242–3.422 mm (KS B 0211), but using this drill does not guarantee that tolerance. Results vary with tool, material and machining conditions, so check with a gauge where needed.
- The recommended drill can vary with material and tap. Follow your tap maker's table.
- Forming (roll) taps need a different hole. Follow the tool maker's table.
- Pilot holes for tapping screws are an entirely different matter. See tapping screw pilot holes.
When an M4 does not fit
- Overseas drawings: Overseas CAD libraries and imported equipment drawings may use ISO dimensions (diameter 8.0, height 3.1). If the head seat was designed to those dimensions, check first.
- Tapping screws: Even when marked 'M4', type 1 and type 2 tapping screws have a different thread and do not fit an M4 internal thread. See tapping screw types.
- Inch screws: Inch screws of similar diameter, such as #8-32, do not fit M4.
What to check when choosing an M4
- Screw type: Use a machine screw if the mating part has an internal thread, and a tapping screw if it drives straight into a hole with no internal thread.
- Head type and seat: Use the table above to check that the head diameter and height fit the assembly space.
- Length: The measuring reference depends on the head. Countersunk heads are measured from the top of the head.
- Material and strength: Check whether stainless or carbon steel is needed, and whether a property class is required. For stainless, see A2 property classes.
- Surface finish: Choose the plating or acid treatment that suits the service environment.
JKF M4 products
- Material: stainless A2 (STS304Cu), carbon steel, SCM435
- Finish: acid treatment, natural and white zinc plating, nickel plating, colored plating
- Length: 4–100 mm for pan head machine screws
Every product page has a drawing and a 3D view. Example M4 pan head · All M4 products
FAQ
What does the M in M4 mean?
It means metric thread. The number is the nominal diameter in mm.
Which driver number does an M4 screw take?
JKF M4 cross-recessed screws take No. 2.
What does M4 × 10 mean?
4 mm diameter and 10 mm length.
References
- KS B 0211 Limits of sizes for metric coarse screw threads — pitch, 6g external and 6H internal thread dimensions (tables 3 and 4)
- KS B 1023:2016 Cross recessed machine screws — annex table A.1, pan head dimensions and tolerances, recess number
- ISO 273:1979 Fasteners — Clearance holes for bolts and screws — clearance hole diameter (fine, medium, coarse)
- ISO 898-1:2013 Fasteners — Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and studs with specified property classes — stress area of coarse threads
Last revised 2026-11-04