Metric coarse threads M1-M100
Metric coarse threads constitute the most widely used screw fastening system worldwide. They are defined in standards ISO 724 and ISO 261, with a symmetrical 60° V profile and a thread depth of 0.614 × pitch. The coarse pitch represents the normal series and may be omitted in the designation; for example, an M10 equals M10 × 1.5. The following table includes all standardized dimensions from M1 to M100, including tap drill diameters, clearance hole diameters, and tensile stress area.
Dimensions according to ISO 724
Section titled “Dimensions according to ISO 724”| Nominal size | Pitch (mm) | Tap drill (mm) | Clearance hole diameter (mm) | Tensile stress area (mm²) |
|---|---|---|---|---|
| M1 | 0,25 mm / 0.0098 in | 0,75 mm / 0.0295 in | 1,2 mm / 0.0472 in | 0,46 mm² / 0.00071 in² |
| M1.2 | 0,25 mm / 0.0098 in | 0,95 mm / 0.0374 in | 1,4 mm / 0.0551 in | 0,73 mm² / 0.00113 in² |
| M1.4 | 0,30 mm / 0.0118 in | 1,10 mm / 0.0433 in | 1,6 mm / 0.0630 in | 0,99 mm² / 0.00153 in² |
| M1.6 | 0,35 mm / 0.0138 in | 1,25 mm / 0.0492 in | 1,8 mm / 0.0709 in | 1,27 mm² / 0.00197 in² |
| M1.8 | 0,35 mm / 0.0138 in | 1,45 mm / 0.0571 in | 2,1 mm / 0.0827 in | 1,70 mm² / 0.00264 in² |
| M2 | 0,40 mm / 0.0157 in | 1,60 mm / 0.0630 in | 2,4 mm / 0.0945 in | 2,07 mm² / 0.00321 in² |
| M2.2 | 0,45 mm / 0.0177 in | 1,75 mm / 0.0689 in | 2,5 mm / 0.0984 in | 2,44 mm² / 0.00378 in² |
| M2.5 | 0,45 mm / 0.0177 in | 2,05 mm / 0.0807 in | 2,9 mm / 0.1142 in | 3,39 mm² / 0.00525 in² |
| M3 | 0,50 mm / 0.0197 in | 2,50 mm / 0.0984 in | 3,4 mm / 0.1339 in | 5,03 mm² / 0.00780 in² |
| M3.5 | 0,60 mm / 0.0236 in | 2,90 mm / 0.1142 in | 3,9 mm / 0.1535 in | 6,78 mm² / 0.0105 in² |
| M4 | 0,70 mm / 0.0276 in | 3,30 mm / 0.1299 in | 4,5 mm / 0.1772 in | 8,78 mm² / 0.0136 in² |
| M4.5 | 0,75 mm / 0.0295 in | 3,75 mm / 0.1476 in | 5,0 mm / 0.1969 in | 11,3 mm² / 0.0175 in² |
| M5 | 0,80 mm / 0.0315 in | 4,20 mm / 0.1654 in | 5,5 mm / 0.2165 in | 14,2 mm² / 0.0220 in² |
| M6 | 1,00 mm / 0.0394 in | 5,00 mm / 0.1969 in | 6,6 mm / 0.2598 in | 20,1 mm² / 0.0312 in² |
| M7 | 1,00 mm / 0.0394 in | 6,00 mm / 0.2362 in | 7,6 mm / 0.2992 in | 28,9 mm² / 0.0448 in² |
| M8 | 1,25 mm / 0.0492 in | 6,80 mm / 0.2677 in | 9,0 mm / 0.3543 in | 36,6 mm² / 0.0567 in² |
| M10 | 1,50 mm / 0.0591 in | 8,50 mm / 0.3346 in | 11,0 mm / 0.4331 in | 58,0 mm² / 0.0899 in² |
| M12 | 1,75 mm / 0.0689 in | 10,20 mm / 0.4016 in | 13,5 mm / 0.5315 in | 84,3 mm² / 0.131 in² |
| M14 | 2,00 mm / 0.0787 in | 12,00 mm / 0.4724 in | 15,5 mm / 0.6102 in | 115 mm² / 0.178 in² |
| M16 | 2,00 mm / 0.0787 in | 14,00 mm / 0.5512 in | 17,5 mm / 0.6890 in | 157 mm² / 0.243 in² |
| M18 | 2,50 mm / 0.0984 in | 15,50 mm / 0.6102 in | 19,5 mm / 0.7677 in | 192 mm² / 0.298 in² |
| M20 | 2,50 mm / 0.0984 in | 17,50 mm / 0.6890 in | 22,0 mm / 0.8661 in | 245 mm² / 0.380 in² |
| M22 | 2,50 mm / 0.0984 in | 19,50 mm / 0.7677 in | 24,0 mm / 0.9449 in | 303 mm² / 0.470 in² |
| M24 | 3,00 mm / 0.1181 in | 21,00 mm / 0.8268 in | 26,0 mm / 1.0236 in | 353 mm² / 0.547 in² |
| M27 | 3,00 mm / 0.1181 in | 24,00 mm / 0.9449 in | 29,0 mm / 1.1417 in | 459 mm² / 0.711 in² |
| M30 | 3,50 mm / 0.1378 in | 26,50 mm / 1.0433 in | 32,0 mm / 1.2598 in | 561 mm² / 0.869 in² |
| M33 | 3,50 mm / 0.1378 in | 29,50 mm / 1.1614 in | 36,0 mm / 1.4173 in | 694 mm² / 1.076 in² |
| M36 | 4,00 mm / 0.1575 in | 32,00 mm / 1.2598 in | 39,0 mm / 1.5354 in | 817 mm² / 1.266 in² |
| M39 | 4,00 mm / 0.1575 in | 35,00 mm / 1.3780 in | 42,0 mm / 1.6535 in | 976 mm² / 1.513 in² |
| M42 | 4,50 mm / 0.1772 in | 37,50 mm / 1.4764 in | 45,0 mm / 1.7717 in | 1120 mm² / 1.736 in² |
| M45 | 4,50 mm / 0.1772 in | 40,50 mm / 1.5945 in | 48,0 mm / 1.8898 in | 1300 mm² / 2.015 in² |
| M48 | 5,00 mm / 0.1969 in | 43,00 mm / 1.6929 in | 51,0 mm / 2.0079 in | 1470 mm² / 2.278 in² |
| M52 | 5,00 mm / 0.1969 in | 47,00 mm / 1.8504 in | 56,0 mm / 2.2047 in | 1760 mm² / 2.728 in² |
| M56 | 5,50 mm / 0.2165 in | 50,50 mm / 1.9882 in | 60,0 mm / 2.3622 in | 2030 mm² / 3.146 in² |
| M60 | 5,50 mm / 0.2165 in | 54,50 mm / 2.1457 in | 64,0 mm / 2.5197 in | 2370 mm² / 3.674 in² |
| M64 | 6,00 mm / 0.2362 in | 58,00 mm / 2.2835 in | 68,0 mm / 2.6772 in | 2680 mm² / 4.154 in² |
| M68 | 6,00 mm / 0.2362 in | 62,00 mm / 2.4409 in | 72,0 mm / 2.8346 in | 3060 mm² / 4.743 in² |
| M72 | 6,00 mm / 0.2362 in | 66,00 mm / 2.5984 in | 77,0 mm / 3.0315 in | 3460 mm² / 5.363 in² |
| M76 | 6,00 mm / 0.2362 in | 70,00 mm / 2.7559 in | 82,0 mm / 3.2283 in | 3890 mm² / 6.029 in² |
| M80 | 6,00 mm / 0.2362 in | 74,00 mm / 2.9134 in | 86,0 mm / 3.3858 in | 4340 mm² / 6.727 in² |
| M85 | 6,00 mm / 0.2362 in | 79,00 mm / 3.1102 in | 91,0 mm / 3.5827 in | 4950 mm² / 7.673 in² |
| M90 | 6,00 mm / 0.2362 in | 84,00 mm / 3.3071 in | 96,0 mm / 3.7795 in | 5590 mm² / 8.664 in² |
| M95 | 6,00 mm / 0.2362 in | 89,00 mm / 3.5039 in | 101,0 mm / 3.9764 in | 6270 mm² / 9.719 in² |
| M100 | 6,00 mm / 0.2362 in | 94,00 mm / 3.7008 in | 106,0 mm / 4.1732 in | 6990 mm² / 10.83 in² |
Stress area and allowable loads
Section titled “Stress area and allowable loads”The tensile stress area determines the load capacity of a bolt. The allowable tensile load is obtained by multiplying the area by the proof stress of the material. For property classes 8.8, 10.9 and 12.9, the following table provides indicative values for the most common coarse thread diameters.
| Size | Tensile area | Proof load 8.8 (kN) | Proof load 10.9 (kN) | Proof load 12.9 (kN) |
|---|---|---|---|---|
| M4 | 8,78 mm² / 0.0136 in² | 5,6 kN / 1259 lbf | 7,3 kN / 1641 lbf | 8,5 kN / 1911 lbf |
| M5 | 14,2 mm² / 0.0220 in² | 9,1 kN / 2046 lbf | 11,8 kN / 2653 lbf | 13,8 kN / 3102 lbf |
| M6 | 20,1 mm² / 0.0312 in² | 12,9 kN / 2900 lbf | 16,7 kN / 3754 lbf | 19,5 kN / 4383 lbf |
| M8 | 36,6 mm² / 0.0567 in² | 23,4 kN / 5261 lbf | 30,4 kN / 6834 lbf | 35,5 kN / 7981 lbf |
| M10 | 58,0 mm² / 0.0899 in² | 37,1 kN / 8341 lbf | 48,1 kN / 10814 lbf | 56,3 kN / 12657 lbf |
| M12 | 84,3 mm² / 0.131 in² | 54,0 kN / 12139 lbf | 70,0 kN / 15735 lbf | 81,8 kN / 18385 lbf |
| M14 | 115 mm² / 0.178 in² | 74,0 kN / 16636 lbf | 96,0 kN / 21583 lbf | 112 kN / 25178 lbf |
| M16 | 157 mm² / 0.243 in² | 100 kN / 22481 lbf | 130 kN / 29222 lbf | 152 kN / 34163 lbf |
| M20 | 245 mm² / 0.380 in² | 157 kN / 35299 lbf | 203 kN / 45634 lbf | 238 kN / 53496 lbf |
| M24 | 353 mm² / 0.547 in² | 226 kN / 50802 lbf | 293 kN / 65863 lbf | 342 kN / 76868 lbf |
| M30 | 561 mm² / 0.869 in² | 359 kN / 80692 lbf | 466 kN / 104744 lbf | 544 kN / 122279 lbf |
| M36 | 817 mm² / 1.266 in² | 523 kN / 117557 lbf | 678 kN / 152403 lbf | 792 kN / 178014 lbf |
| M42 | 1120 mm² / 1.736 in² | 717 kN / 161143 lbf | 930 kN / 209041 lbf | 1090 kN / 244994 lbf |
| M48 | 1470 mm² / 2.278 in² | 941 kN / 211493 lbf | 1220 kN / 274214 lbf | 1430 kN / 321443 lbf |
Note: Proof loads are based on stresses of 640 MPa (8.8), 830 MPa (10.9) and 970 MPa (12.9) and do not replace detailed calculation according to the application. For lubricated bolts, adjust with torque coefficient recommendations.
Standard equivalences
Section titled “Standard equivalences”Metric coarse threads correspond to the following international references:
- ISO 724: Basic dimensions, identical to the normal series of ISO 261.
- DIN 13‑1 (Germany): Historical equivalent and still widely referenced in Europe.
- ANSI/ASME B1.13M: American version of the same thread; however, it should not be confused with inch threads UNC/UNF. There is no direct mechanical interchangeability with any of those systems.
| Designation | Pitch (mm) | ISO 724 / DIN 13‑1 | ANSI B1.13M (Metric) | Comparable inch threads* |
|---|---|---|---|---|
| M6 | 1,00 mm / 0.0394 in | M6 | M6×1 | 1/4″‑20 UNC (not interchangeable) |
| M8 | 1,25 mm / 0.0492 in | M8 | M8×1.25 | 5/16″‑18 UNC (not interchangeable) |
| M10 | 1,50 mm / 0.0591 in | M10 | M10×1.5 | 3/8″‑16 UNC (not interchangeable) |
| M12 | 1,75 mm / 0.0689 in | M12 | M12×1.75 | 1/2″‑13 UNC (not interchangeable) |
| M16 | 2,00 mm / 0.0787 in | M16 | M16×2 | 5/8″‑11 UNC (not interchangeable) |
The listed UNC threads are only the closest in nominal size, but the profile, pitches and diameters are incompatible.
Recommended tightening torques
Section titled “Recommended tightening torques”The values in the table have been calculated for hex head bolts, in dry condition (μ = 0.15) and lubricated (μ = 0.10), and property class 8.8. For other classes, multiply according to the proof stress ratio.
| Size | Dry torque (N·m) | Dry torque (ft·lb) | Lubricated torque (N·m) | Lubricated torque (ft·lb) |
|---|---|---|---|---|
| M4 | 2,2 N·m / 1.6 ft·lb | 1,6 ft·lb | 1,6 N·m / 1.2 ft·lb | 1,2 ft·lb |
| M5 | 4,5 N·m / 3.3 ft·lb | 3,3 ft·lb | 3,4 N·m / 2.5 ft·lb | 2,5 ft·lb |
| M6 | 7,6 N·m / 5.6 ft·lb | 5,6 ft·lb | 5,7 N·m / 4.2 ft·lb | 4,2 ft·lb |
| M8 | 18 N·m / 13.3 ft·lb | 13,3 ft·lb | 14 N·m / 10.3 ft·lb | 10,3 ft·lb |
| M10 | 36 N·m / 26.5 ft·lb | 26,5 ft·lb | 27 N·m / 19.9 ft·lb | 19,9 ft·lb |
| M12 | 63 N·m / 46.5 ft·lb | 46,5 ft·lb | 47 N·m / 34.7 ft·lb | 34,7 ft·lb |
| M14 | 100 N·m / 73.7 ft·lb | 73,7 ft·lb | 75 N·m / 55.3 ft·lb | 55,3 ft·lb |
| M16 | 155 N·m / 114 ft·lb | 114 ft·lb | 116 N·m / 85.6 ft·lb | 85,6 ft·lb |
| M20 | 305 N·m / 225 ft·lb | 225 ft·lb | 229 N·m / 169 ft·lb | 169 ft·lb |
| M24 | 525 N·m / 387 ft·lb | 387 ft·lb | 394 N·m / 291 ft·lb | 291 ft·lb |
| M30 | 1040 N·m / 767 ft·lb | 767 ft·lb | 780 N·m / 575 ft·lb | 575 ft·lb |
| M36 | 1800 N·m / 1328 ft·lb | 1328 ft·lb | 1350 N·m / 996 ft·lb | 996 ft·lb |
The torques are indicative and assume a constant friction coefficient. Always validate with manufacturer specifications and the tightening method.
Clearance hole drill sizes
Section titled “Clearance hole drill sizes”The clearance hole diameter follows ISO 273, with three fits: fine, medium and coarse. It is used to accommodate the bolt without thread and allow its assembly.
| Size | Fine fit (mm) | Fine fit (in) | Medium fit (mm) | Medium fit (in) | Coarse fit (mm) | Coarse fit (in) |
|---|---|---|---|---|---|---|
| M1.6 | 1,7 mm / 0.0669 in | 0.0669 in | 1,8 mm / 0.0709 in | 0.0709 in | 2,0 mm / 0.0787 in | 0.0787 in |
| M3 | 3,2 mm / 0.1260 in | 0.1260 in | 3,4 mm / 0.1339 in | 0.1339 in | 3,6 mm / 0.1417 in | 0.1417 in |
| M4 | 4,3 mm / 0.1693 in | 0.1693 in | 4,5 mm / 0.1772 in | 0.1772 in | 4,8 mm / 0.1890 in | 0.1890 in |
| M5 | 5,3 mm / 0.2087 in | 0.2087 in | 5,5 mm / 0.2165 in | 0.2165 in | 5,8 mm / 0.2283 in | 0.2283 in |
| M6 | 6,4 mm / 0.2520 in | 0.2520 in | 6,6 mm / 0.2598 in | 0.2598 in | 7,0 mm / 0.2756 in | 0.2756 in |
| M8 | 8,4 mm / 0.3307 in | 0.3307 in | 9,0 mm / 0.3543 in | 0.3543 in | 10,0 mm / 0.3937 in | 0.3937 in |
| M10 | 10,5 mm / 0.4134 in | 0.4134 in | 11,0 mm / 0.4331 in | 0.4331 in | 12,0 mm / 0.4724 in | 0.4724 in |
| M12 | 13,0 mm / 0.5118 in | 0.5118 in | 13,5 mm / 0.5315 in | 0.5315 in | 14,5 mm / 0.5709 in | 0.5709 in |
| M16 | 17,0 mm / 0.6693 in | 0.6693 in | 17,5 mm / 0.6890 in | 0.6890 in | 18,5 mm / 0.7283 in | 0.7283 in |
| M20 | 21,0 mm / 0.8268 in | 0.8268 in | 22,0 mm / 0.8661 in | 0.8661 in | 24,0 mm / 0.9449 in | 0.9449 in |
| M24 | 25,0 mm / 0.9843 in | 0.9843 in | 26,0 mm / 1.0236 in | 1.0236 in | 28,0 mm / 1.1024 in | 1.1024 in |
Values are rounded to the nearest tenth of a millimeter and follow common practice in general mechanical construction.
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the pitch of an M10 coarse thread bolt?
Section titled “What is the pitch of an M10 coarse thread bolt?”The standard pitch for an M10 coarse thread is 1.5 mm / 0.0591 in. This pitch is the only one in the normal series and therefore does not need to be specified on the drawing.
What drill should be used to tap an M8 hole?
Section titled “What drill should be used to tap an M8 hole?”The recommended tap drill is 6.80 mm / 0.2677 in. It corresponds to the nominal diameter minus the pitch (8 mm – 1.25 mm = 6.75 mm), rounded according to ISO 724.
What is the actual major diameter of an M24 thread?
Section titled “What is the actual major diameter of an M24 thread?”The nominal major diameter is 24 mm / 0.9449 in, although the upper manufacturing limit is usually a few hundredths below (≈ 23.83 mm for class 6g).
What tightening torque does a dry M12 class 8.8 bolt require?
Section titled “What tightening torque does a dry M12 class 8.8 bolt require?”63 N·m / 46.5 ft·lb is recommended for dry conditions (μ ≈ 0.15). For lubricated bolts the value drops to 47 N·m / 34.7 ft·lb.
What is the tensile stress area of an M6 bolt?
Section titled “What is the tensile stress area of an M6 bolt?”The effective tensile area is 20.1 mm² / 0.0312 in². This allows it to withstand a proof load in class 8.8 of approximately 12.9 kN / 2900 lbf.
Under which standards are metric coarse threads manufactured?
Section titled “Under which standards are metric coarse threads manufactured?”The basic dimension is defined by ISO 724, equivalent to DIN 13‑1. In the United States the same thread is covered as a metric series in ANSI B1.13M, although it never coincides with UNC/UNF threads.