Overview
ISO 8745:1997 defines the characteristics of half-length taper grooved pins used as fasteners in mechanical assemblies. The standard covers pins made of steel and austenitic stainless steel with three equally spaced longitudinal grooves and nominal diameters from 1.5 mm to 25 mm inclusive. The displaced material from the grooves forms an expanded diameter that produces a non-positive locking fit when the pin is pressed into a hole of the nominal diameter.
Key Topics
- Dimensions and range: Nominal diameter (d) 1.5 mm to 25 mm; details of expanded diameter and length are specified.
- Groove form: Three longitudinal grooves equally spaced; grooving angle (70°) applies to steel and may be modified for other materials depending on resilience.
- Materials and hardness:
- Steel: specified hardness range (reported in standard) and provisions for surface treatment.
- Austenitic stainless steel (grade A1): different hardness range specified in the standard (see ISO 3506-1 for fastener grades).
- Fit and tolerance: Hole diameter should equal the nominal pin diameter and conform to tolerance class H11. The expanded diameter can be checked using a GO/NO GO ring gauge for acceptance testing.
- Surface finish and coatings: Preferred coatings for steel include black oxide, phosphate conversion coatings or zinc plating with chromate conversion (refer to ISO 9717 and ISO 4042). Stainless pins are typically supplied in plain natural finish or with protective lubricant.
- Testing and acceptance: Shear strength testing follows ISO 8749; acceptance inspection follows ISO 3269.
Applications
Grooved pins standardized to ISO 8745:1997 provide predictable mechanical behaviour and are commonly used for:
- Locating and securing mating components where a press-fit is acceptable
- Transmitting shear loads in assemblies where easy assembly and removal are required
- Applications requiring corrosion-resistant options by selecting austenitic stainless steel grades
Practical benefits include consistent fit, defined shear strength expectations, and simplified supplier–buyer designation and procurement.
Related Standards
- ISO 3269 - Acceptance inspection for fasteners
- ISO 3506-1 - Corrosion-resistant stainless steel fasteners (grades and hardness)
- ISO 4042 - Electroplated coatings for fasteners (reference)
- ISO 8749 - Shear test for pins and grooved pins
- ISO 9717 - Phosphate conversion coatings
Designations in the standard provide a concise ordering format (example: “Grooved pin ISO 8745 – 6 · 50 – St” for a steel pin). Use these standardized designations and referenced tests to ensure interchangeability and consistent performance when specifying grooved pins.