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Internally Threaded Dowel Pin Dimensions (ISO 8735 / DIN 7979, 6 to 50 mm)

Guide · Updated October 28, 2026

ISO 8735 covers hardened dowel pins with an internal extraction thread (it replaced DIN 7979), 6 to 50 mm. Values agree between the ISO 8735:1997 preview (iTeh, English and French) and the DIN EN ISO 8735 sheet from pinfastener.com. Boltport and fasteners.eu publish the older DIN 7979 values and were not used. Check your supplier for critical work.

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Step by step

Pick the pin diameter: d1 (m6), 6 to 50 mm; ream the hole to H7.
Read the extraction thread: d2 and pitch P, e.g. M6 x 1 for a 10 mm pin.
Check thread and hole depth: t1 is the full thread depth and t2 min the depth of the tapped hole.
Pick a puller: Use a puller or a screw of size d2 that reaches into t1.
Order it: Designate as Parallel pin ISO 8735 - 6 x 30 - A - St (type A through hardened, type B case hardened).

ISO 8735 threaded dowel pin dimensions (mm)

Columns: diameter d1 (m6), chamfer a ≈, end radius length c, thread d2, pitch P, counterbore d3, thread depth t1, hole depth t2 min, counterbore depth t3.

d1 | a | c | d2 | P | d3 | t1 | t2 min | t3
6 | 0.8 | 2.1 | M4 | 0.7 | 4.3 | 6 | 10 | 1
8 | 1 | 2.6 | M5 | 0.8 | 5.3 | 8 | 12 | 1.2
10 | 1.2 | 3 | M6 | 1 | 6.4 | 10 | 16 | 1.2
12 | 1.6 | 3.8 | M6 | 1 | 6.4 | 12 | 20 | 1.2
16 | 2 | 4.6 | M8 | 1.25 | 8.4 | 16 | 25 | 1.5
20 | 2.5 | 6 | M10 | 1.5 | 10.5 | 18 | 28 | 1.5
25 | 3 | 6 | M16 | 2 | 17 | 24 | 35 | 2
30 | 4 | 7 | M20 | 2.5 | 21 | 30 | 40 | 2
40 | 5 | 8 | M20 | 2.5 | 21 | 30 | 40 | 2.5
50 | 6.3 | 10 | M24 | 3 | 25 | 36 | 50 | 2.5

Worked example: 10 mm threaded dowel

A 10 x 40 ISO 8735 pin in a blind H7 hole has an M6 x 1 thread 10 mm deep (tapped hole at least 16 mm deep), so an M6 puller bolt pulls it out.

Common problems

Pin stuck in a blind hole: vent the hole or use this threaded pin.
Puller thread strips: use the full t1 depth, not just a few threads.
Wrong thread from an old DIN 7979 catalog: check d2 at 16 and 20 mm.

FAQ

What is ISO 8735?

Hardened parallel (dowel) pins with an internal thread for pulling them out of blind holes, 6 to 50 mm. It replaced DIN 7979.

How is it different from ISO 8734?

Same hardened m6 pin, plus a tapped hole in one end so it can be pulled from a blind hole.

Are old DIN 7979 threads the same?

Not at every size. Supplier tables based on DIN 7979 list M8 at 16 mm with a 12 mm thread and M10 at 20 mm with a 16 mm thread, where ISO 8735 gives 16 and 18 mm. The chart uses ISO 8735.

What is d3?

The counterbore diameter at the thread entry; t3 is its depth.

What was skipped?

Per-diameter length ranges (the preview shows them as an unreadable graphic) and old DIN 7979 values. Length tolerance is ±0.5 mm up to 50 mm and ±0.75 mm above.

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