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Torx Socket Head Cap Screw Dimensions (ISO 14579, M2 to M12)

Guide · Updated October 28, 2026

ISO 14579 covers hexalobular (Torx) socket head cap screws, M2 to M20, product grade A; this chart shows M2 to M12. Values agree across the ISO 14579:2011 published table, the Inoxmare datasheet, and the mesh-iit CAD library. Max values; A is reference.

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Step by step

Find the thread: Pick the row for your thread size, M2 to M12.
Pick the bit: Use the Torx size shown, e.g. T30 for M6, T45 for M8.
Size the counterbore: Head diameter dk and height k match ISO 4762, so standard SHCS counterbores work.
Check engagement: Seat the bit fully; t max is the socket depth.

ISO 14579 Torx socket head cap screw dimensions (mm)

Columns: thread d, pitch P, plain head diameter dk max, head height k max, Torx socket No., socket width A (ref.), socket depth t max.

Size | P | dk | k | Torx | A | t
M2 | 0.4 | 3.8 | 2 | T6 | 1.75 | 0.84
M2.5 | 0.45 | 4.5 | 2.5 | T8 | 2.4 | 1.04
M3 | 0.5 | 5.5 | 3 | T10 | 2.8 | 1.27
M4 | 0.7 | 7 | 4 | T20 | 3.95 | 1.8
M5 | 0.8 | 8.5 | 5 | T25 | 4.5 | 2.03
M6 | 1 | 10 | 6 | T30 | 5.6 | 2.42
M8 | 1.25 | 13 | 8 | T45 | 7.95 | 3.31
M10 | 1.5 | 16 | 10 | T50 | 8.95 | 4.02
M12 | 1.75 | 18 | 12 | T55 | 11.35 | 5.21

Worked example: M6 fixture screw

An M6 ISO 14579 head is 10 mm across and 6 mm tall, the same as ISO 4762, so an existing M6 SHCS counterbore fits. Drive it with a T30 bit; the socket is up to 2.42 mm deep.

Common problems

Bit does not fit: ISO 14579 needs a Torx (T) bit, not a hex key; check the T size per row.
Lobes strip: worn bit, or a TR/Torx Plus bit; use a good-fit standard T bit seated fully.
Wrong head size assumed: dk and k match ISO 4762, not the low-head DIN 7984 / DIN 6912 styles.

FAQ

Torx vs hex socket head cap screw?

ISO 14579 uses the same head dk and k as ISO 4762 (DIN 912); only the drive changes from hex to hexalobular, which takes more torque with less cam-out and wear.

Is there a DIN number?

It is published as DIN EN ISO 14579; there is no separate legacy DIN dimension table.

Why is dk sometimes 13.27 for M8?

That is the maximum for knurled heads. Plain heads are 13.00 max; this chart lists plain heads.

Why stop at M12?

ISO 14579 runs to M20, but M14 to M20 values could not be confirmed in a second source, so they are left out.

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General shop information only — follow your drawing, tool maker's data and your quality system.