ISO 8062-4:2023

Overview

ISO 8062-4:2023 - Geometrical product specifications (GPS) - Part 4 - defines the rules and general tolerances for castings using profile tolerancing in a general datum system. The standard covers geometrical dimensioning and tolerancing (GD&T) for final moulded parts and parts machined from moulded parts, including conventions for graphical symbols, proportions of symbols, and presentation in technical product documentation. It specifies general surface profile tolerances tied to a general datum system that remains on the final part, plus required machining allowances (RMA) and draft angle (taper) grades for cast metals and alloys. NOTE: the standard is not applicable when cast datum surfaces are subsequently machined.

Key topics and technical requirements

• General tolerancing approach: Uses surface profile tolerances in a general datum system to control size, form, orientation and location for castings and moulded parts.
• Graphical symbols & presentation: Defines symbols and their proportions for product-definition indications (different and larger than surface texture symbols per ISO 21920-1).
• Product definition types: Clarifies single/combined product definitions and indicators for final moulded, intermediate machined, and final machined conditions.
• Machining allowance (RMA): Specifies general and individual RMA rules to ensure adequate material for secondary machining.
• Draft angles (tapers): Defines draft/taper grades and symbols, including symmetric/unsymmetrical tolerance zones.
• Rules and decision logic: Presents Rules A–I covering application of general tolerances, surface profile tolerances, datum system (RST), overrides, additional tolerances, machined condition, RMA, drafts, and wall thickness.
• 2D and 3D applicability: Primary figures are 2D, but tolerancing principles are applicable to 3D CAD/CAM and inspection workflows.
• Normative and informative annexes: Include symbol dimensions, calculation methods for nominal dimensions, example drawings, multiple tolerancing method and guidance on selecting tolerances and RMAs.

Practical applications and users

ISO 8062-4:2023 is essential for:

• Foundry and casting engineers specifying tolerances on casting drawings
• Design engineers and CAD modelers who must define cast part tolerances and draft requirements
• Manufacturing engineers setting machining allowances and process planning
• Quality, inspection and metrology teams verifying form and profile tolerances against a general datum system
• Procurement and suppliers producing castings to specified GPS requirements

Typical uses: preparing technical product documentation (2D drawings and 3D models), defining required machining allowance and draft angles, applying general surface profile tolerances, and ensuring consistent GD&T for cast and machined-from-casting parts.

Related standards

• ISO 1101, ISO 5458, ISO 5459 (GD&T fundamentals)
• ISO 8015 (fundamental rules of GPS) and ISO 14253-1 (decision rules)
• ISO 14638 (GPS matrix model)
• ISO 21920-1 (surface texture symbols - replaces ISO 1302)
• Other parts of ISO 8062 series (dimensional tolerances for moulded and cast parts)

Keywords: ISO 8062-4:2023, geometrical product specifications, GPS, castings, profile tolerancing, general datum system, moulded parts, machining allowance, draft angle, surface profile tolerance.