ISO 8742:1997

Overview

ISO 8742:1997 is an international standard specifying the characteristics of one-third-length centre grooved pins used in mechanical fastenings. These grooved pins, made from steel or austenitic stainless steel, feature three equally spaced longitudinal grooves along a third of their length, providing a non-positive locking fit when inserted into a drilled hole with dimensions matching the pin's nominal diameter. This standard covers pins with diameters ranging from 1.5 mm up to 25 mm.

The standard, issued by the International Organization for Standardization (ISO) and developed by Technical Committee ISO/TC 2 (Fasteners), ensures consistent quality, dimensions, and performance characteristics for grooved pins, critical components in various engineering and manufacturing applications.

Key Topics

Characteristics and Dimensions

• Pins have three centre grooves uniformly spaced over one-third of their length.
• Nominal diameters covered: 1.5 mm to 25 mm inclusive.
• Pins produce an expanded diameter due to grooves, ensuring a locking fit in corresponding holes.
• Exact dimensions, tolerances, and expanded diameters are detailed, facilitating standardized production and interchangeability.

Material and Finish

• Material: Carbon steel and austenitic stainless steel.
• Hardness ranges specified for steel (125 HV30 to 245 HV30) and stainless steel grades (210 HV30 to 280 HV30).
• Surface finishes may include natural, black oxide, phosphate coatings, or zinc plating with chromate conversion coatings.
• Protective lubricants can be applied unless otherwise specified.

Testing and Quality

• Shear strength requirements defined, with testing procedures referenced to ISO 8749.
• Acceptance inspection according to ISO 3269 ensures only compliant pins are delivered.
• Pins must be free from defects or irregularities impacting performance.

Designation and Marking

• Standardized designation format includes pin type, nominal diameter, length, and material grade.
• Example: "Grooved pin ISO 8742 – 6 · 50 – St" indicates a steel pin of 6 mm diameter and 50 mm length.

Applications

ISO 8742:1997 standard grooved pins are widely used in mechanical assemblies requiring secure, slip-resistant axial joining without the use of threaded fasteners. Typical applications include:

• Machinery and automotive component assembly.
• Electrical and electronic fastening where precise positioning is essential.
• Aerospace and industrial equipment requiring reliable shear strength and locking.
• Construction of tools and fixtures demanding repeatable and robust fastening solutions.

Their expansion feature in drilled holes makes them suitable for non-permanent but highly reliable positioning, key in safety-critical and load-bearing joint applications.

Related Standards

• ISO 3269:1988 – Fasteners – Acceptance inspection.
• ISO 3506-1:1997 – Corrosion-resistant stainless steel fasteners – Specification for bolts, screws, and studs.
• ISO 4042 – Fasteners – Electroplated coatings (under revision).
• ISO 8749:1986 – Pins and grooved pins – Shear test methods.
• ISO 9717:1990 – Phosphate conversion coatings for metals – Specification methods.

These referenced standards complement ISO 8742 by providing test methods, material properties, corrosion protection, and quality acceptance procedures essential for manufacturing and deploying grooved pins in diverse environments.

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