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Taper Pin with Internal Thread Dimensions (ISO 8736 / DIN 7978, 6 to 50 mm)
Guide · Updated October 28, 2026
ISO 8736 covers unhardened 1:50 taper pins with an internal extraction thread (it replaced DIN 7978), 6 to 50 mm. The values agree between the ISO 8736:1986 preview (iTeh) and the Engineering Hardware ISO 8736 table. Boltsfastener and Briol DIN 7978 agree on d2, a, t1 and t2 to 16 mm. Check your supplier for critical work.
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Step by step
- Pick the taper size: d1 (h10) is the small-end diameter, 6 to 50 mm; ream with a 1:50 taper reamer.
- Read the thread: d2 x P in the large end, e.g. M6 x 1 for a 10 mm pin.
- Check depths: t1 is the full thread depth, t2 min the tapped hole depth.
- Check the counterbore: d3 is the counterbore diameter and t3 its depth.
- Order it: Designate as Taper pin ISO 8736 - A - 10 x 60 - St (A ground, B turned).
ISO 8736 internally threaded taper pin dimensions (mm)
Columns: taper diameter d1 (h10), chamfer a ≈, thread d2, pitch P, counterbore d3, thread depth t1, hole depth t2 min, counterbore depth t3.
- d1 | a | d2 | P | d3 | t1 | t2 min | t3
- 6 | 0.8 | M4 | 0.7 | 4.3 | 6 | 10 | 1
- 8 | 1 | M5 | 0.8 | 5.3 | 8 | 12 | 1.2
- 10 | 1.2 | M6 | 1 | 6.4 | 10 | 16 | 1.2
- 12 | 1.6 | M8 | 1.25 | 8.4 | 12 | 20 | 1.2
- 16 | 2 | M10 | 1.5 | 10.5 | 16 | 25 | 1.5
- 20 | 2.5 | M12 | 1.75 | 13 | 18 | — | 1.5
- 25 | 3 | M16 | 2 | 17 | 24 | 35 | 2
- 30 | 4 | M20 | 2.5 | 21 | 30 | 40 | 2
- 40 | 5 | M20 | 2.5 | 21 | 30 | 40 | 2.5
- 50 | 6.3 | M24 | 3 | 25 | 36 | 50 | 2.5
Worked example: 10 mm internal-thread taper pin
A 10 x 60 ISO 8736 pin has an M6 x 1 thread 10 mm deep in a tapped hole at least 16 mm deep. Thread an M6 puller in to draw it out of a blind tapered hole.
Common problems
- Pin stands proud: ream deeper with the 1:50 taper reamer.
- Puller strips: engage the full t1 depth.
- Old DIN 7978 stock: hole depth at 20 mm may be 27, not 28 mm.
FAQ
What is ISO 8736?
Unhardened 1:50 taper pins with a tapped hole in the large end so they can be pulled from blind holes, 6 to 50 mm. It replaced DIN 7978.
How is it different from ISO 8737?
ISO 8737 has a threaded stem; ISO 8736 has an internal thread and sits flush.
Why is t2 dashed at 20 mm?
ISO 8736 gives 28 mm; DIN 7978 catalogs (Boltsfastener, Briol) give 27 mm. The sources conflict, so it is dashed.
Type A or B?
Type A is ground (Ra 0.8 µm), type B turned (Ra 3.2 µm).
What was skipped?
Per-size length ranges, and t2 at 20 mm. The thread is 6H.
Related guides and calculators
- Threaded taper pins (ISO 8737 / DIN 7977)
- Metric taper pin chart (ISO 2339)
- Threaded dowel pins (ISO 8735 / DIN 7979)
- Metric dowel pin chart (ISO 8734)
- All free machinist calculators
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