ISO 6344-2:2021

Overview

ISO 6344-2:2021 specifies a standardized method for determining and designating the grain size distribution (particle size distribution, PSD) of macrogrit used in coated abrasives. It covers electro‑fused aluminium oxide and silicon carbide macrogrits in sizes P12 to P220. The standard defines a comparative sieving analysis using a prescribed nest of test sieves (see Table 1 in the standard), reference Macro‑P‑Mastergrits and the criteria for acceptance of grit lots or grits extracted from coated abrasive products.

Keywords: ISO 6344-2:2021, coated abrasives, grain size distribution, macrogrit P12–P220, sieving analysis, Macro‑P‑Mastergrits.

Key topics and technical requirements

• Scope and materials: Applies to electro‑fused aluminium oxide and silicon carbide macrogrits used in manufacture or recovered from coated abrasive products.
• Grain size designation: Grain size distribution for each P size (P12–P220) is defined in Table 1 with required residue ranges across five sieves and the bottom pan.
• Test method: Comparative sieve analysis using Macro‑P‑Mastergrits and the test portion on the same nest of sieves (Clause 5). Test sieving machines shall conform to ISO 9284.
• Sampling and preparation: Test portions are dried at 105 °C until constant weight; standard test portion is 100 g (minimum 20 g for recovered grains). Sampling/splitting in accordance with ISO 9138.
• Apparatus and tolerances: Utility sieves per ISO 3310‑1; balance accuracy ≥ ±0.1 g; sieving time controlled (5 min with ±5 s allowance). Macro‑P‑Mastergrits are reference materials with certified sieving reports and tighter tolerances.
• Evaluation criteria: Defined limits for residues on individual sieves and cumulative residues (Q values). All material must pass the coarsest designated sieve (Q = 0 for sieve 1); additional limits for sieves 2–5 and pan remainder are specified in the standard.
• Quality control: Procedures to check serviceability of utility test sieves using Macro‑P‑Mastergrits and correction of sieve-specific values.

Applications and users

ISO 6344-2:2021 is intended for:

• Coated abrasive manufacturers (quality control, specification compliance)
• Test laboratories and QA/QC departments performing PSD analysis on abrasive grits
• Raw material suppliers certifying electro‑fused aluminium oxide or silicon carbide grits
• R&D teams optimizing abrasive formulations and process control
• Procurement/specification engineers who require standardized grit designation

Practical benefits include reproducible PSD data, consistent product labelling (P sizes), improved process control, and easier supplier verification.

Related standards

• ISO 3310‑1 - Test sieves (metal wire cloth)
• ISO 9138 - Abrasive grains - Sampling and splitting
• ISO 9284 - Abrasive grains - Test-sieving machines
• Other parts of ISO 6344 (microgrit or additional methods) for complete coated abrasives grading

Using ISO 6344-2:2021 ensures harmonized, traceable testing and clear designation of macrogrit PSD for coated abrasive products.