← AskMachinist · Guides · Calculator · 🔎 Search
Full-Length Parallel Grooved Pin Dimensions (ISO 8740 / DIN 1473, 1.5 to 25 mm)
Guide · Updated October 28, 2026
ISO 8740 covers full-length parallel grooved pins with chamfer (it replaced DIN 1473), 1.5 to 25 mm. Values agree between the ISO 8740:1997 preview (iTeh) and the fasteners.eu ISO 8740 table. Boltport also agrees on c1, c2 and a up to 12 mm. Check your supplier for critical work.
Need an exact reference size?
Build any gage block stack with the free Gage Block Calculator. Free, no login.
Step by step
- Pick the pin size: d1, 1.5 to 25 mm; drill the hole to d1 (H11 typical).
- Check the expanded diameter: d2 is the diameter over the raised groove edges on a steel pin; check it with a GO/NO GO ring gauge.
- Read the ends: c1 and c2 are the chamfer and pilot at the leading end, a the chamfer at the other end.
- Check the load: Minimum double shear strength is for steel pins.
- Order it: Designate as Grooved pin ISO 8740 - 6 x 30 - St.
ISO 8740 parallel grooved pin dimensions (mm)
Columns: nominal d1, tolerance, chamfer c1 ≈, pilot length c2 ≈, end chamfer a ≈, expanded diameter d2 (steel), minimum double shear (kN, steel).
- d1 | tol | c1 | c2 | a | d2 | shear kN
- 1.5 | h9 | 0.12 | 0.6 | 0.2 | 1.6 | 1.6
- 2 | h9 | 0.18 | 0.8 | 0.25 | 2.15 | 2.84
- 2.5 | h9 | 0.25 | 1 | 0.3 | 2.65 | 4.4
- 3 | h9 | 0.3 | 1.2 | 0.4 | 3.2 | 6.4
- 4 | h11 | 0.4 | 1.4 | 0.5 | 4.25 | 11.3
- 5 | h11 | 0.5 | 1.7 | 0.63 | 5.25 | 17.6
- 6 | h11 | 0.6 | 2.1 | 0.8 | 6.3 | 25.4
- 8 | h11 | 0.8 | 2.6 | 1 | 8.3 | 45.2
- 10 | h11 | 1 | 3 | 1.2 | 10.35 | 70.4
- 12 | h11 | 1.2 | 3.8 | 1.6 | 12.35 | 101.8
- 16 | h11 | 1.6 | 4.6 | 2 | 16.4 | 181
- 20 | h11 | 2 | 6 | 2.5 | 20.5 | 283
- 25 | h11 | 2.5 | 7.5 | 3 | 25.5 | 444
Worked example: 6 mm grooved pin
A 6 x 30 ISO 8740 steel pin goes in a plain 6 mm drilled hole. Its grooves raise it to 6.3 mm, which gives the locking fit, and it holds at least 25.4 kN in double shear.
Common problems
- Pin loose: hole oversize; drill to d1, do not ream larger.
- Pin will not start: lead with the pilot end (c2).
- Stainless pin loose: stainless d2 is smaller; ask your supplier for the value.
FAQ
What is ISO 8740?
Grooved pins with three full-length parallel grooves and a chamfered pilot, 1.5 to 25 mm. They lock by elastic fit in a plain drilled hole. It replaced DIN 1473.
Which edition is this?
ISO 8740:1997. The 2025 edition slightly raised d2 on the shortest lengths and added stainless values and extra sizes, so check your supplier for 2025 stock.
Why is d2 one value per size?
Parallel grooves give the same expanded diameter over all lengths; it applies to steel pins only. Stainless pins are slightly smaller.
Why not DIN 1471 / ISO 8744?
Taper grooved pins have d2 that changes with length, and the sources did not agree, so that chart is held.
What was skipped?
Per-size length ranges (stepped lines in the preview) and d2 for stainless steel.
Related guides and calculators
- Round head grooved pins (ISO 8746)
- Grooved pins with pilot (ISO 8739)
- Parallel pins (ISO 2338 / DIN 7)
- Metric dowel pin chart (ISO 8734)
- Slotted spring pin chart (ISO 8752)
- Coiled spring pin chart (ISO 8748)
- Metric clevis pins (ISO 2341 / DIN 1444)
- All free machinist calculators
Build your stack in seconds
The free Gage Block Calculator finds the fewest-block combination for inch and metric sets, with wear blocks. No login.
Questions? Ask a machinist.
General shop information only — follow your drawing, tool maker's data and your quality system.