ISO 8737:1986

Overview

ISO 8737:1986 specifies the characteristics, dimensions and designation of taper pins with external thread, unhardened. The standard covers metric taper pins with nominal diameters from 5 mm to 50 mm and tabulates corresponding thread sizes M5 to M50 and nominal lengths from 40 mm up to 400 mm (with larger lengths by agreement). ISO 8737:1986 is intended for use by manufacturers, designers and quality inspectors of mechanical fasteners and fittings.

Key Topics

• Scope and sizes: Metric nominal diameters d1 = 5–50 mm; thread sizes M5…M50; nominal lengths typically 40–400 mm (longer lengths by agreement or in 40 mm steps above 400 mm).
• Thread and tolerances: Metric screw thread with tolerance 6g in accordance with ISO 965.
• Material and hardness: Default material is free‑cutting steel (St) with specified hardness 125–245 HV; other materials may be agreed between customer and supplier.
• Surface finish and coatings: Pins may be supplied plain with rust‑preventative lubricant or with preferred coatings such as black oxide, phosphate coating, or zinc plating with chromate conversion (see ISO 2081 and ISO 4520). All dimensional tolerances apply prior to plating or coating.
• Workmanship and inspection: Parts must be uniform and free of defects; no burrs allowed. Taper inspection is performed using an optical comparator. Acceptance inspection follows ISO 3269.
• Designation example: Taper pin ISO 8737 - 6 x 50 - St (unhardened steel taper pin, 6 mm × 50 mm).

Applications

ISO 8737 taper pins with external thread are used where precise location and mechanical fastening are required. Typical practical applications and users include:

• Mechanical and machine design engineers specifying location pins and fasteners
• Fastener manufacturers producing metric taper pins to international dimensions
• Quality assurance and inspection teams verifying tolerances and surface finish
• Maintenance, assembly and tooling operations requiring removable locating pins in jigs, fixtures, gear and shaft assemblies

Using ISO 8737 ensures interchangeability, reliable fit, and consistent quality for taper pins, improving procurement clarity and reducing assembly issues.

Related Standards

• ISO 965 - General purpose metric screw threads - Tolerances (thread tolerance 6g)
• ISO 2081 - Electroplated zinc coatings (referenced for zinc plating)
• ISO 4520 - Chromate conversion coatings on electroplated zinc and cadmium
• ISO 3269 - Fasteners - Acceptance inspection

Keywords: ISO 8737, taper pins, external thread, unhardened taper pin, metric taper pins, fasteners, thread tolerance, free‑cutting steel, surface finish, acceptance inspection.