Overview
ISO 8746:1997 specifies the characteristics of round-head grooved pins used as fasteners. These pins have three equally spaced longitudinal grooves and nominal diameters from 1.4 mm to 20 mm inclusive. The displaced material at the grooves forms an expanded diameter larger than the nominal diameter, producing a non-positive locking fit when the pin is driven into a hole of nominal diameter (tolerance class H11).
Key characteristics in the standard include allowed materials, surface finishes, hardness for cold-heading steel, dimensional limits and designation conventions. Acceptance inspection is referenced to ISO 3269.
Key Topics
- Nominal diameters: 1.4 mm to 20 mm inclusive.
- Grooves: Three equally spaced longitudinal grooves; grooving angle of 70° applies to grooved pins made from steel and may be modified for other materials depending on resilience.
- Expanded diameter (d2): Greater than nominal diameter (d1); testing of d2 is performed using a GO/NO-GO ring gauge as noted in the standard.
- Types: Type A (chamfered end) and Type B (pilot end). Type selection can be by supplier discretion or specified by the customer.
- Materials: Cold-heading steel (St) with hardness range 125 HV30 to 245 HV30 is specified; other materials may be agreed between customer and supplier.
- Surface finish & coatings: Pins are normally supplied plain with protective lubricant unless otherwise specified. Preferred coatings include black oxide, phosphate conversion coatings or zinc plating with chromate. Conversion coatings referenced: ISO 9717 and ISO 4042.
- Tolerances & hole fit: The mating hole diameter should equal the nominal pin diameter and conform to tolerance class H11.
- Workmanship & acceptance: Pins must be free from detrimental defects; acceptance inspection follows ISO 3269.
Applications
ISO 8746 grooved pins are used where a non-positive locking fit is acceptable and simple, reliable axial retention is required. Typical applications include:
- Mechanical assemblies requiring temporary or semi-permanent axial location
- Components where quick assembly and standardised pin sizing ease production and supply
- Use in assemblies where shear load resistance and ease of insertion are priorities
Benefits:
- Interchangeability through standardised dimensions and designation
- Consistent retention due to expanded diameter and groove design
- Supply chain clarity by referencing ISO 8746:1997 in procurement and drawings
Related Standards
- ISO 3269 - Fasteners: Acceptance inspection (acceptability procedures)
- ISO 4042 - Fasteners: Electroplated coatings (surface treatment guidance)
- ISO 9717 - Phosphate conversion coatings (specification of conversion coatings)
For specification, ordering and quality inspection, reference ISO 8746:1997 directly and include required type, nominal diameter and length in the designation (example: "Grooved pin ISO 8746 – 6 · 30 – St").
