ISO 8736:1986

Overview

ISO 8736:1986 specifies unhardened taper pins with internal thread in metric sizes. The standard covers nominal diameters from 6 mm to 50 mm and tabulates corresponding internal thread sizes (M6 to M50) and nominal lengths (16 mm up to 200 mm). Two manufacturing types are defined - Type A (ground) and Type B (turned) - with specified surface finishes and requirements for material, coatings, tolerances and inspection. An example designation format is given (e.g., Taper pin ISO 8736 - A - 6 x 30 - St).

Key topics and technical requirements

• Dimensional range: Nominal diameters d1 = 6–50 mm; thread sizes M6–M50; nominal lengths typically 16–200 mm (steps and extended lengths noted).
• Types and surface finish:
  • Type A - ground, surface finish R = 0.8 µm (preferred for precision fits).
  • Type B - turned, surface finish R = 3.2 µm.
• Thread specification: Metric internal thread tolerance 6H in accordance with ISO 965.
• Materials and finish:
  • Typical material: steel (designation example uses “St”).
  • Plain (natural) finish with rust-preventative lubricant unless otherwise agreed.
  • Preferred coatings: black oxide, phosphate, or zinc plating with chromate conversion (see ISO 2081, ISO 4520).
  • All tolerances apply prior to plating/coating.
• Workmanship and quality:
  • Pins must be uniform, free of detrimental defects and burrs.
  • Taper inspection: by suitable optical comparator or equivalent method.
• References: ISO 965 (threads), ISO 2081 (zinc plating), ISO 3269 (acceptance inspection), ISO 4520 (chromate conversion).

Applications and who uses this standard

ISO 8736 is used by:

• Mechanical designers and machine builders specifying locating and fastening elements.
• Manufacturing and production engineers selecting precision taper pins for alignment, positioning or removable joints.
• Fastener suppliers and procurement teams ensuring standardized parts for interchangeability.
• Quality control and inspection teams applying the defined tolerances, surface finishes and inspection methods. Practical applications include alignment pins in assemblies, jigs and fixtures, machine-tool components, and other mechanical joints where a tapered locating pin with an internal thread is required for removal or secure fastening.

Related standards

• ISO 965 - General-purpose metric screw threads - Tolerances
• ISO 2081 - Metallic coatings - Electroplated zinc on iron/steel
• ISO 3269 - Fasteners - Acceptance inspection
• ISO 4520 - Chromate conversion coatings on electroplated coatings

Keywords: ISO 8736, taper pins with internal thread, unhardened taper pins, metric taper pins, fasteners standard, taper pin dimensions, surface finish, thread 6H.