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Metric fine threads table

Metric fine pitch threads belong to the ISO thread family and are characterized by having a smaller pitch than the coarse pitch version for the same nominal diameter. The thread depth is 0,54125 times the pitch and the thread angle is 60°, in accordance with ISO 68-1. This type of thread offers a larger cross-sectional area and better fine adjustment capability, therefore it is used in applications requiring higher vibration resistance, thin walls or precision adjustments, such as in the automotive, aerospace and machinery industries.

Metric fine thread dimensions table

Section titled “Metric fine thread dimensions table”

The following table compiles the fundamental dimensions of metric fine pitch threads according to ISO 724 and ISO 261, including nominal diameter, pitch, tap drill diameter and tensile stress area.

Nominal diameter Pitch Tap drill diameter Tensile stress area
M3 x 0,35 0,35 mm / 0.014 in 2,60 mm / 0.102 in 4,7 mm² / 0.0073 in²
M4 x 0,50 0,50 mm / 0.020 in 3,50 mm / 0.138 in 9,0 mm² / 0.0140 in²
M5 x 0,50 0,50 mm / 0.020 in 4,50 mm / 0.177 in 16,1 mm² / 0.0250 in²
M6 x 0,75 0,75 mm / 0.030 in 5,20 mm / 0.205 in 20,1 mm² / 0.0312 in²
M8 x 0,75 0,75 mm / 0.030 in 7,20 mm / 0.283 in 39,2 mm² / 0.0608 in²
M8 x 1,00 1,00 mm / 0.039 in 7,00 mm / 0.276 in 39,2 mm² / 0.0608 in²
M10 x 0,75 0,75 mm / 0.030 in 9,20 mm / 0.362 in 64,5 mm² / 0.1000 in²
M10 x 1,00 1,00 mm / 0.039 in 9,00 mm / 0.354 in 64,5 mm² / 0.1000 in²
M10 x 1,25 1,25 mm / 0.049 in 8,80 mm / 0.346 in 61,2 mm² / 0.0949 in²
M12 x 1,00 1,00 mm / 0.039 in 11,00 mm / 0.433 in 92,1 mm² / 0.1428 in²
M12 x 1,25 1,25 mm / 0.049 in 10,80 mm / 0.425 in 92,1 mm² / 0.1428 in²
M12 x 1,50 1,50 mm / 0.059 in 10,50 mm / 0.413 in 88,1 mm² / 0.1366 in²
M14 x 1,50 1,50 mm / 0.059 in 12,50 mm / 0.492 in 135 mm² / 0.209 in²
M16 x 1,00 1,00 mm / 0.039 in 15,00 mm / 0.591 in 178 mm² / 0.276 in²
M16 x 1,50 1,50 mm / 0.059 in 14,50 mm / 0.571 in 167 mm² / 0.259 in²
M18 x 1,50 1,50 mm / 0.059 in 16,50 mm / 0.650 in 216 mm² / 0.335 in²
M20 x 1,50 1,50 mm / 0.059 in 18,50 mm / 0.728 in 272 mm² / 0.422 in²
M20 x 2,00 2,00 mm / 0.079 in 18,00 mm / 0.709 in 258 mm² / 0.400 in²
M24 x 1,50 1,50 mm / 0.059 in 22,50 mm / 0.886 in 401 mm² / 0.622 in²
M24 x 2,00 2,00 mm / 0.079 in 22,00 mm / 0.866 in 384 mm² / 0.595 in²
M27 x 2,00 2,00 mm / 0.079 in 25,00 mm / 0.984 in 496 mm² / 0.769 in²
M30 x 2,00 2,00 mm / 0.079 in 28,00 mm / 1.102 in 621 mm² / 0.963 in²
M30 x 3,00 3,00 mm / 0.118 in 27,00 mm / 1.063 in 581 mm² / 0.901 in²
M36 x 2,00 2,00 mm / 0.079 in 34,00 mm / 1.339 in 915 mm² / 1.418 in²
M36 x 3,00 3,00 mm / 0.118 in 33,00 mm / 1.299 in 865 mm² / 1.341 in²
M42 x 3,00 3,00 mm / 0.118 in 39,00 mm / 1.535 in 1210 mm² / 1.876 in²
M48 x 3,00 3,00 mm / 0.118 in 45,00 mm / 1.772 in 1600 mm² / 2.480 in²
M56 x 4,00 4,00 mm / 0.157 in 52,00 mm / 2.047 in 2150 mm² / 3.333 in²
M64 x 4,00 4,00 mm / 0.157 in 60,00 mm / 2.362 in 2850 mm² / 4.418 in²
Section titled “Recommended tightening torques”

The torque values shown correspond to metric fine pitch bolts with hex head, lightly lubricated and tightened dry. The figures are based on using 75% of the proof load according to property class 8.8 and 10.9.

Diameter x pitch Torque class 8.8 Torque class 10.9
M3 x 0,35 1,2 Nm / 0.9 ft·lb 1,8 Nm / 1.3 ft·lb
M4 x 0,50 2,8 Nm / 2.1 ft·lb 4,0 Nm / 3.0 ft·lb
M5 x 0,50 5,5 Nm / 4.1 ft·lb 8,0 Nm / 5.9 ft·lb
M6 x 0,75 9,5 Nm / 7.0 ft·lb 14 Nm / 10 ft·lb
M8 x 0,75 18 Nm / 13 ft·lb 26 Nm / 19 ft·lb
M8 x 1,00 25 Nm / 18 ft·lb 35 Nm / 26 ft·lb
M10 x 1,00 49 Nm / 36 ft·lb 69 Nm / 51 ft·lb
M10 x 1,25 47 Nm / 35 ft·lb 66 Nm / 49 ft·lb
M12 x 1,00 77 Nm / 57 ft·lb 110 Nm / 81 ft·lb
M12 x 1,25 85 Nm / 63 ft·lb 120 Nm / 89 ft·lb
M12 x 1,50 81 Nm / 60 ft·lb 115 Nm / 85 ft·lb
M14 x 1,50 130 Nm / 96 ft·lb 185 Nm / 136 ft·lb
M16 x 1,50 200 Nm / 148 ft·lb 285 Nm / 210 ft·lb
M18 x 1,50 280 Nm / 207 ft·lb 395 Nm / 291 ft·lb
M20 x 1,50 395 Nm / 291 ft·lb 560 Nm / 413 ft·lb
M20 x 2,00 375 Nm / 277 ft·lb 530 Nm / 391 ft·lb
M24 x 2,00 670 Nm / 494 ft·lb 950 Nm / 701 ft·lb
M30 x 2,00 1090 Nm / 804 ft·lb 1540 Nm / 1136 ft·lb

Tap drill sizes for internal threads

Section titled “Tap drill sizes for internal threads”

For the preparation of the hole prior to tapping, a drill whose diameter approximates the minor diameter of the thread should be used. The following table details the recommended drill diameters for the most common fine threads, including the clearance hole diameter for a pass-through element.

Nominal diameter x pitch Recommended drill Clearance hole drill
M4 x 0,50 3,50 mm / 0.138 in 4,30 mm / 0.169 in
M5 x 0,50 4,50 mm / 0.177 in 5,30 mm / 0.209 in
M6 x 0,75 5,20 mm / 0.205 in 6,40 mm / 0.252 in
M8 x 0,75 7,20 mm / 0.283 in 8,40 mm / 0.331 in
M8 x 1,00 7,00 mm / 0.276 in 8,40 mm / 0.331 in
M10 x 1,00 9,00 mm / 0.354 in 10,50 mm / 0.413 in
M10 x 1,25 8,80 mm / 0.346 in 10,50 mm / 0.413 in
M12 x 1,25 10,80 mm / 0.425 in 13,00 mm / 0.512 in
M12 x 1,50 10,50 mm / 0.413 in 13,00 mm / 0.512 in
M14 x 1,50 12,50 mm / 0.492 in 15,00 mm / 0.591 in
M16 x 1,50 14,50 mm / 0.571 in 17,00 mm / 0.669 in
M18 x 1,50 16,50 mm / 0.650 in 19,00 mm / 0.748 in
M20 x 1,50 18,50 mm / 0.728 in 21,00 mm / 0.827 in
M24 x 2,00 22,00 mm / 0.866 in 25,00 mm / 0.984 in
M30 x 2,00 28,00 mm / 1.102 in 31,00 mm / 1.220 in

Equivalences between DIN, ISO and ANSI standards

Section titled “Equivalences between DIN, ISO and ANSI standards”

Metric fine pitch threads are internationally regulated by ISO 724, which establishes the basic dimensions, and by ISO 261, which defines the preferred range of diameters and pitches. In the European context, DIN 13 is technically identical to ISO and covers the same profiles and tolerances; in fact, most recent editions of DIN 13 reflect the content of the corresponding ISO standards.

In the American system, ASME B1.13M fully adopts the profile and dimensions of ISO metric threads, so an M10 x 1,25 bolt manufactured under ASME B1.13M is completely interchangeable with one manufactured under ISO 724 or DIN 13. The equivalence is not based on a conversion to UNC/UNF threads, but on the direct adoption of the metric system.

Frequently Asked Questions (FAQ)

Section titled “Frequently Asked Questions (FAQ)”

What is the thread depth in the basic profile of a metric fine pitch thread?

Section titled “What is the thread depth in the basic profile of a metric fine pitch thread?”

The depth is equal to 0,614 times the nominal pitch; for example, on an M10 x 1,25 thread the theoretical thread depth is 0,767 mm / 0.030 in.

How is a metric fine pitch thread distinguished from a coarse pitch thread on the same diameter?

Section titled “How is a metric fine pitch thread distinguished from a coarse pitch thread on the same diameter?”

A fine pitch M10 bolt has a pitch of 1,00 mm or 1,25 mm, while the standard coarse pitch is 1,50 mm. The designation is written including the pitch, for example M10 x 1,00, while M10 without pitch indication is assumed coarse pitch.

How much larger is the tensile stress area of a fine thread compared to a coarse thread?

Section titled “How much larger is the tensile stress area of a fine thread compared to a coarse thread?”

In a fine M12 x 1,25 the tensile stress area is 92,1 mm², versus 84,3 mm² for coarse pitch M12 x 1,75, which represents an increase of 9,2 %.

Section titled “What maximum tightening torque is recommended for an M8 x 1,00 class 8.8 bolt?”

The maximum suggested torque for M8 x 1,00 class 8.8 is 25 Nm / 18 ft·lb under light lubrication and dry tightening conditions.

What is the correct drill for making a pilot hole for tapping a female M12 x 1,5 thread?

Section titled “What is the correct drill for making a pilot hole for tapping a female M12 x 1,5 thread?”

It is recommended to use a 10,50 mm / 0.413 in drill, which corresponds to the theoretical minor diameter of the thread.

In which diameters are extra fine pitch combinations offered?

Section titled “In which diameters are extra fine pitch combinations offered?”

Extra fine pitch combinations (for example 0,75 mm on M10 or 1,00 mm on M16) are standardized in ISO 261 and are used when thin wall or micrometric adjustment is required, being available from M1 up to at least M100.

References

Section titled “References”