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Socket Shoulder Screw Dimensions (ISO 7379, 6.5 to 25 mm)

Guide · Updated October 28, 2026

ISO 7379 covers hexagon socket head shoulder screws with shoulder diameters 6.5 to 25 mm. Values agree across Fuller Fasteners, RC Fastener and Brighton-Best ISO 7379 tables. Shoulder tolerance is f9; dk is the knurled-head maximum.

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Step by step

Pick the shoulder: Choose the shoulder diameter ds your part needs, 6.5 to 25 mm; the thread is set by it.
Check the fit: The shoulder is f9: e.g. 10 mm runs 9.951 to 9.987 mm; size the bore to suit.
Pick the key: Use s for the hex key, e.g. 5 mm for the 10 mm shoulder.
Tap the hole: Tap for the thread d deeper than b max so the shoulder seats.

ISO 7379 socket shoulder screw dimensions (mm)

Columns: nominal shoulder ds, thread d, shoulder ds max and min (f9), head diameter dk max, head height k max, hex key s, socket depth t min, thread length b max.

ds | d | ds max | ds min | dk max | k max | s | t min | b max
6.5 | M5 | 6.487 | 6.451 | 10.22 | 4.5 | 3 | 2.4 | 9.75
8 | M6 | 7.987 | 7.951 | 13.27 | 5.5 | 4 | 3.3 | 11.25
10 | M8 | 9.987 | 9.951 | 16.27 | 7 | 5 | 4.2 | 13.25
13 | M10 | 12.984 | 12.941 | 18.27 | 9 | 6 | 4.9 | 16.4
16 | M12 | 15.984 | 15.941 | 24.33 | 11 | 8 | 6.6 | 18.4
20 | M16 | 19.98 | 19.928 | 30.33 | 14 | 10 | 8.8 | 22.4
25 | M20 | 24.98 | 24.928 | 36.39 | 16 | 12 | 10 | 27.4

Worked example: 10 x 40 shoulder screw

A 10 x 40 ISO 7379 screw has a 9.951 to 9.987 mm shoulder 40 mm long, an M8 thread up to 13.25 mm long, a 16.27 mm max head 7 mm tall and takes a 5 mm hex key.

Common problems

Wrong length: shoulder length excludes the thread; do not order by overall length.
Shoulder will not seat: the tapped hole is too shallow for b max.
Tight bore: the f9 shoulder is under nominal; ream the bore to the fit you need.
Stripped key: use the full socket depth t with the right hex key.

FAQ

How is a shoulder screw sized?

By shoulder diameter and shoulder length, e.g. 10 x 40. Length is under the head to the end of the shoulder and excludes the thread.

Why is the thread smaller than the shoulder?

The shoulder seats against the tapped part; e.g. a 10 mm shoulder has an M8 thread.

What tolerance is the shoulder?

f9, so it is always slightly under nominal; e.g. the 16 mm shoulder is 15.941 to 15.984 mm.

What does dk max mean here?

It is the maximum head diameter for knurled heads, e.g. 16.27 mm for the 10 mm shoulder; allow that in counterbores.

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