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Full-Length Parallel Grooved Pin with Pilot Dimensions (ISO 8739, 1.5 to 25 mm)
Guide · Updated October 28, 2026
ISO 8739 covers full-length parallel grooved pins with pilot, 1.5 to 25 mm. Values agree between the ISO 8739:1997 preview (iTeh) and the fasten.it DIN EN ISO 8739 table. Check your supplier for critical work.
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Step by step
- Pick the pin size: d1, 1.5 to 25 mm; drill the hole to d1, tolerance H11.
- Check the expanded diameter: d2 is the diameter over the groove edges on a steel pin. It is one value for all lengths. Check it with a GO/NO GO ring gauge.
- Lead with the pilot: c (min to max) is the pilot length at the leading end. a is the chamfer at the other end.
- Order it: Designate as Grooved pin ISO 8739 - 6 x 30 - St.
ISO 8739 grooved pin with pilot dimensions (mm)
Columns: nominal d1, pilot length c max and c min, end chamfer a ≈, expanded diameter d2 (steel, all lengths).
- d1 | c max | c min | a | d2
- 1.5 | 2 | 1 | 0.2 | 1.6
- 2 | 2 | 1 | 0.25 | 2.15
- 2.5 | 2.5 | 1.5 | 0.3 | 2.65
- 3 | 2.5 | 1.5 | 0.4 | 3.2
- 4 | 3 | 2 | 0.5 | 4.25
- 5 | 3 | 2 | 0.63 | 5.25
- 6 | 4 | 3 | 0.8 | 6.3
- 8 | 4 | 3 | 1 | 8.3
- 10 | 5 | 4 | 1.2 | 10.35
- 12 | 5 | 4 | 1.6 | 12.35
- 16 | 5 | 4 | 2 | 16.4
- 20 | 7 | 6 | 2.5 | 20.5
- 25 | 7 | 6 | 3 | 25.5
Worked example: 6 mm grooved pin with pilot
A 6 x 30 ISO 8739 steel pin goes in a 6 mm H11 drilled hole. Start it with the 3 to 4 mm pilot. The grooves raise it to 6.3 mm, which gives the locking fit.
Common problems
- Pin loose: hole oversize; drill to d1, do not ream larger.
- Pin cocks on entry: lead with the pilot end.
- Stainless pin loose: stainless d2 is smaller; ask your supplier.
FAQ
What is ISO 8739?
Grooved pins with three full-length parallel grooves and a pilot end for easy insertion, 1.5 to 25 mm. They lock by elastic fit in a plain H11 drilled hole.
How is it different from ISO 8740?
ISO 8740 has a chamfer point (c1, c2). ISO 8739 has a longer pilot, c. a and d2 are the same in both.
Which edition is this?
ISO 8739:1997. The 2025 edition has diamond grooves and changes some d2 values, so check your supplier for 2025 stock.
Why no shear or tolerance column?
Only the ISO preview lists them. Our second source (fasten.it) does not, so we left them out instead of shipping single-source values. Stainless d2 and length ranges are also skipped.
Related guides and calculators
- Round head grooved pins (ISO 8746)
- Parallel grooved pins (ISO 8740 / DIN 1473)
- Parallel pins (ISO 2338 / DIN 7)
- Metric dowel pin chart (ISO 8734)
- Slotted spring pin chart (ISO 8752)
- Coiled spring pin chart (ISO 8748)
- All free machinist calculators
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