The ISO metric screw threads are the most commonly used type of general-purpose screw thread worldwide, The "M" designation for metric screws indicates the nominal outer diameter of the screw thread, in millimeter. two types of thread pitch coarse and fine screw thread.
ISO 261 specifies a detailed list of preferred combinations of outer diameter D and pitch P for ISO metric screw threads. The 1st choice column follows (approximately) the R10 series from ISO 3, while the 2nd choice column are rounded off values from the R20 series from ISO 3.
ISO 262 specifies a shorter list of thread dimensions – a subset of ISO 261.
ISO 262 selected sizes for screws, bolts and nuts
Nominal diameter | Pitch | ||
1st | 2nd | Coarse | Fine |
1 | 0.25 | 0.2 | |
1.2 | 0.25 | 0.2 | |
1.4 | 0.3 | 0.2 | |
1.6 | 0.35 | 0.2 | |
1.8 | 0.35 | 0.2 | |
2 | 0.4 | 0.25 | |
2.5 | 0.45 | 0.35 | |
3 | 0.5 | 0.35 | |
3.5 | 0.6 | 0.35 | |
4 | 0.7 | 0.5 | |
0.8 | 0.5 | ||
5.5DIN13 | 0.9 | 0.5 | |
1 | 0.75 | ||
7 | 1 | 0.75 | |
1.25 | 1or0.75 | ||
10 | 1.5 | 1.25or1 | |
12 | 1.75 | 1.5or1.25 | |
14 | 2 | 1.5 | |
16 | 2 | 1.5 | |
|18 | 2.5 | 2or1.5 | |
20 | 2.5 | 2or1.5 | |
22 | 2.5 | 2or1.5 | |
24 | 3 | 2 | |
27 | 3 | 2 | |
30 | 3.5 | 2 | |
33 | 3.5 | 2 | |
36 | 4 | 3 | |
39 | 4 | 3 | |
42 | 4.5 | 3 | |
45 | 4.5 | 3 | |
48 | 5 | 3 | |
52 | 5 | 4 | |
56 | 5.5 | 4 | |
|60 | 5.5 | 4 | |
64 | 6 | 4 | |
Spanner (wrench) sizes mm
Below are some common spanner (wrench) sizes for metric screw threads. Hex head widths (width across flats, spanner size) are for DIN 934 hex nuts and hex head bolts. Other (usually smaller) sizes may occur for reasons of weight and cost reduction.
| | | | | |
Size | ISO | DIN | |||
M1 | - | 2.5 | - | - | - |
M1.2 | - | 3 | - | - | - |
M1.4 | - | 3 | 1.25 | - | 0.7 |
M1.6 | 3.2 | 3.2 | 1.5 | 0.9 | 0.7 |
M2 | 4 | 4 | 1.5 | 1.25 | 0.9 |
M2.5 | 5 | 5 | 2 | 1.5 | 1.3 |
M3 | 5.5 | 5.5 | 2.5 | 2 | 1.5 |
M3.5 | 6 | 6 | - | - | - |
M4 | 7 | 7 | 3 | 2.5 | 2 |
M5 | 8 | 8 | 4 | 3 | 2.5 |
M6 | 10 | 10 | 5 | 4 | 3 |
M7 | 11 | 11 | - | - | - |
M8 | 13 | 13 | 6 | 5 | 4 |
M10 | 16 | 17 | 8 | 6 | 5 |
M12 | 18 | 19 | 10 | 8 | 6 |
M14 | 21 | 22 | 10 | - | - |
M16 | 24 | 24 | 14 | 10 | 8 |
M18 | 27 | 27 | 14 | 12 | - |
M20 | 30 | 30 | 17 | 12 | 10 |
M22 | 34 | 32 | 17 | 14 | - |
M24 | 36 | 36 | 19 | 14 | 12 |
M27 | 41 | 41 | 19 | 17 | 14 |
M30 | 46 | 46 | 22 | 17 | 14 |
M33 | 50 | 50 | 24 | - | - |
M36 | 55 | 55 | 27 | - | - |
M39 | 60 | 60 | - | - | - |
M42 | 65 | 65 | 32 | - | - |
M45 | 70 | 70 | - | - | - |
M48 | 75 | 75 | 36 | - | - |
M52 | 80 | 80 | 36 | - | - |
M56 | 85 | 85 | 41 | - | - |
M60 | 90 | 90 | - | - | - |
M64 | 95 | 95 | 46 | - | - |
