DIN 94 / ISO 1234 Split Cotter Pins
Split cotter pins per DIN 94 / ISO 1234 — the paired-prong retaining clip slotted through a drilled fastener and bent back, nominal sizes M0.6 through M20 in the collected table with d, prong length a, eye width b and c tolerances per size.
Last updated: 2026-11
Specifications
A split cotter pin (circlip pin, cotter pin) is a folded half-round wire formed into an eye with two prongs: it slots through a cross-hole in a bolt or shaft and its prongs are bent apart so the assembly cannot back off. It is the cheapest positive lock in the fastener box — castle nuts (DIN 935) and slotted round nuts are designed around it, and it doubles as a shaft-retaining clip on clevises, yokes and linkages. DIN 94 covers the metric series and the collected table cross-references ISO 1234. Sizes run M0.6 to M20 (the collected table marks the M0.6–M1.2 prong-width b column as reference values, not standardized); the c dimension is the pin diameter that must match the cross-hole. Bending back the prongs deforms the pin — cotter pins are single-use: once removed, fit a new one.
| Standard | DIN 94 — ISO equivalent ISO 1234 (split cotter pins) |
|---|---|
| Size range | M0.6, M0.8, M1, M1.2, M1.6, M2, M2.5, M3.2, M4, M5, M6.3, M8, M10, M13, M16, M20 (nominal diameter d = cross-hole diameter) |
| Pin diameter d (max/min by size) | max 0.5 to 19.3 mm, min 0.4 to 19 mm across the M0.6–M20 series — see per-size table |
| Prong length a (max/min by size) | max 1.6–6.3 mm, min 0.8–3.2 mm across the series — see per-size table |
| Eye width b (≈ by size) | 2 to 40 mm across the series; the M0.6–M1.2 b values are marked reference values in the collected table |
| Head / c dimension (max/min by size) | c max 1–38.6 mm, c min 0.9–33.8 mm across the series |
| Installation | Insert through the cross-hole and bend both prongs back — one prong over the fastener, one along the shank; re-bending for reuse is not recommended (the fold work-hardens and cracks) |
| Nominal diameter d | d max (mm) | d min (mm) | a max (mm) | a min (mm) | b approx. (mm) | c max (mm) | c min (mm) |
|---|---|---|---|---|---|---|---|
| M0.6 | 0.5 | 0.4 | 1.6 | 0.8 | 2 | 1 | 0.9 |
| M0.8 | 0.7 | 0.6 | 1.6 | 0.8 | 2.4 | 1.4 | 1.2 |
| M1 | 0.9 | 0.8 | 1.6 | 0.8 | 3 | 1.8 | 1.6 |
| M1.2 | 1 | 0.9 | 2.5 | 1.25 | 3 | 2 | 1.7 |
| M1.6 | 1.4 | 1.3 | 2.5 | 1.25 | 3.2 | 2.8 | 2.4 |
| M2 | 1.8 | 1.7 | 2.5 | 1.25 | 4 | 3.6 | 3.2 |
| M2.5 | 2.3 | 2.1 | 2.5 | 1.25 | 5 | 4.6 | 4 |
| M3.2 | 2.9 | 2.7 | 3.2 | 1.6 | 6.4 | 5.8 | 5.1 |
| M4 | 3.7 | 3.5 | 4 | 2 | 8 | 7.4 | 6.5 |
| M5 | 4.6 | 4.4 | 4 | 2 | 10 | 9.2 | 8 |
| M6.3 | 5.9 | 5.7 | 4 | 2 | 12.6 | 11.8 | 10.3 |
| M8 | 7.5 | 7.3 | 4 | 2 | 16 | 15 | 13.1 |
| M10 | 9.5 | 9.3 | 6.3 | 3.2 | 20 | 19 | 16.6 |
| M13 | 12.4 | 12.1 | 6.3 | 3.2 | 26 | 24.8 | 21.7 |
| M16 | 15.4 | 15.1 | 6.3 | 3.2 | 32 | 30.8 | 27 |
| M20 | 19.3 | 19 | 6.3 | 3.2 | 40 | 38.6 | 33.8 |
| Nominal Size (Pin Hole Dia.) | Max Pin Dia. (d max) | Min Pin Dia. (d min) | Max Extended Prong (a max) | Min Extended Prong (a min) | Eye Length (b) | Eye Outer Dia. Max (c max) | Eye Outer Dia. Min (c min) | Length Max (l max) | Length Nom. (l nom) | Length Min (l min) | Corresponding Bolt Dia. (over) | Corresponding Bolt Dia. (to) | Corresponding Clevis Pin Dia. |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.6 | 0.5 | 0.4 | 1.6 | 0.8 | 2 | 1.0 | 0.9 | 4.5 | 4 | 3.5 | over / - | 2.5 / 2 | over / - |
| 0.8 | 0.7 | 0.6 | 1.6 | 0.8 | 2.4 | 1.4 | 1.2 | 5.5 | 5 | 4.5 | over / 2.5 | 3.5 / 3 | over / 2 |
| 1 | 0.9 | 0.8 | 1.6 | 0.8 | 3 | 1.8 | 1.6 | 6.5 | 6 | 5.5 | over / 3.5 | 4.5 / 4 | over / 3 |
| 1.2 | 1.0 | 0.9 | 2.50 | 1.25 | 3 | 2.0 | 1.7 | 8.5 | 8 | 7.5 | over / 4.5 | 5.5 / 5 | over / 4 |
| 1.6 | 1.4 | 1.3 | 2.50 | 1.25 | 3.2 | 2.8 | 2.4 | 8.5 | 8 | 7.5 | over / 5.5 | 7 / 6 | over / 5 |
| 2 | 1.8 | 1.7 | 2.50 | 1.25 | 4 | 3.6 | 3.2 | 10.5 | 10 | 9.5 | over / 7 | 9 / 8 | over / 6 |
| 2.5 | 2.3 | 2.1 | 2.50 | 1.25 | 5 | 4.6 | 4.0 | 13 | 12 | 11 | over / 9 | 11 / 9 | over / 8 |
| 3.2 | 2.9 | 2.7 | 3.2 | 1.6 | 6.4 | 5.8 | 5.1 | 15 | 14 | 13 | over / 11 | 14 / 12 | over / 9 |
| 4 | 3.7 | 3.5 | 4 | 2 | 8 | 7.4 | 6.5 | 19 | 18 | 17 | over / 14 | 20 / 17 | over / 12 |
| 5 | 4.6 | 4.4 | 4 | 2 | 10 | 9.2 | 8.0 | 23 | 22 | 21 | over / 20 | 27 / 23 | over / 17 |
| 6.3 | 5.9 | 5.7 | 4 | 2 | 12.6 | 11.8 | 10.3 | 33.5 | 32 | 30.5 | over / 27 | 39 / 29 | over / 23 |
| 8 | 7.5 | 7.3 | 4 | 2 | 16 | 15.0 | 13.1 | 41.5 | 40 | 38.5 | over / 39 | 56 / 44 | over / 29 |
| 10 | 9.5 | 9.3 | 6.30 | 3.15 | 20 | 19.0 | 16.6 | 46.6 | 45 | 43.5 | over / 56 | 80 / 69 | over / 44 |
| 13 | 12.4 | 12.1 | 6.30 | 3.15 | 26 | 24.8 | 21.7 | 72.5 | 71 | 69.5 | over / 80 | 120 / 110 | over / 69 |
| 16 | 15.4 | 15.1 | 6.30 | 3.15 | 32 | 30.8 | 27.0 | 114 | 112 | 110 | over / 120 | 170 / 160 | over / 110 |
| 20 | 19.3 | 19.0 | 6.30 | 3.15 | 40 | 38.5 | 33.8 | 162 | 160 | 158 | over / 170 | - | over / 160 |
- Row 16 (20): The M20 row's corresponding-bolt "to" cell prints "-" in the source (truncated value) — reproduced verbatim; the pairing for M20 is incomplete in the source.
- Row 1 (0.6): The bolt and clevis pairing columns print compound tokens ("over / x" / "y / z") in the source, flattening a two-line range header — reproduced verbatim; read each token as "over A / to B".
Materials
- Material and finish specified per RFQ — the collected specification table covers geometry only
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (DIN 94 / ISO 1234 Split Cotter Pins) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantities and lead times for this family are confirmed at quotation — send your sizes, grades and quantities on the RFQ and the quote will carry a firm schedule. Sample availability is confirmed with the quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
What size cotter pin fits my bolt?
The cotter pin is sized by the cross-hole, not the bolt thread: the nominal size M-number equals the hole diameter the pin is meant for (an M3.2 cotter pin goes through a 3.2 mm hole). The collected DIN 94 / ISO 1234 table gives the actual pin body diameter per size — for M3.2 that is 2.7–2.9 mm — because the folded pin is thinner than its nominal size. If you are starting from the fastener, a castle or slotted nut chart names the matching cotter size per thread; if starting from an existing hole, select the size whose nominal matches the drill diameter.
Can a split cotter pin be reused after removal?
No — treat it as a single-use part. The lock works because the prongs are bent apart at installation; that bend work-hardens the wire, and a second bend at the same point is where a removed pin cracks or fatigues in service. Cotter pins are among the cheapest parts in the assembly and their failure mode (a shed prong lets the nut walk off) is disproportionate to their price, so standard practice on servicing is to fit new pins and note them as renewal items on the drawing.
What should an RFQ for this pin type state?
State the pin type, the standard designation (DIN 94 / ISO 1234 or DIN 1470), the nominal size and length, material if the drawing names one, and quantity per size — plus destination country. Commercial terms are confirmed at quotation.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support