BS ISO 6344-2:2021 pdf download – Coated abrasives — Determination and designation of grain size distribution Part 2: Macrogrit sizes P12 to P220
5 Test method of macrogrit sizes P12 to P220
5.1 Macro-P-Mastergrits Macro‑P‑Mastergrits 1) are well-defined reference grits, being associated with test reports of the grain size distribution. The test reports shall be determined in cooperative interlaboratory tests. These cooperative interlaboratory tests shall be supervised by an independent institution like for example the MPA 1) . This institution is responsible for defining the values in the test reports. The apparatus for measuring the values of grain size distribution shall be a test sieving machine according to 5.2.1.
The Macro‑P‑Mastergrits are used for the comparative sieving procedure for testing for coated abrasive products. The grain size distribution of the Macro-P-Mastergrits is specified in Table 1, with the tolerances for Q 3 and Q 4 being only half of the indicated value in Table 1 (e.g. for P20, the tolerance of Q 3 is ±4). Each supply of Macro‑P‑Mastergrits shall be accompanied by a test report giving the sieving analysis and the respective date of test of the Macro‑P‑Mastergrits. The Macro‑P‑Mastergrits are made of fused aluminium oxide. They shall be checked on a test sieving machine according to 5.2.1, with their precisely calibrated series of test sieves. These test sieves correspond to the nominal dimensions of the aperture sizes in accordance with the test sieve designation in Table 1. They are optically measured and considered as reference basis for the testing of grain sizes for coated abrasive products.
5.2 Apparatus
5.2.1 Test sieving machine, shall be in accordance with ISO 9284 giving reproducible and comparable results. EXAMPLE RO‑TAP® test sieving machines are examples of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of these products.
5.2.2 Time switch, controlling the test sieving machine for a period of 5 min. The permissible accuracy shall be ±5 s.
5.2.3 Balance, with an accuracy not less than ±0,1 g shall be used.
5.2.4 Utility test sieves, with openings specified in Table 1. They shall be in accordance with ISO 3310‑1.
5.3 Checking of the common use utility test sieves Common use utility test sieves shall be free from visible defects such as textural flaws (gaps, broken wires etc.), insufficient tension of the fabric, distortions of the frame (out of roundness, leaks and soldering defects) and free from blinding as these will impair the sieving results. Macro‑P‑Mastergrits shall be used for checking the serviceability of these test sieves within the meaning of this document. They shall achieve reproducible test results in the test with Macro‑P‑Mastergrits.
The utility test sieve to be tested shall be mounted into the respective nest of sieves as the 3rd sieve. The 1st sieve and the 2nd sieve shall be checked sieves. The sum of the residues on the 1st, 2nd and 3rd sieve shall not deviate from the Macro‑P‑Mastergrit value by more than 1,5 times the tolerance according to Table 1. Sieves which cannot be inserted as 3rd sieve when assembled in the nest of test sieves according to Table 1, shall be tested as 4th sieve. In this case it shall be ensured that the 1st, 2nd and 3rd sieves are checked sieves.
The sum of the residues on test sieves 1, 2, 3 and 4 shall not deviate from the Macro‑P‑ Mastergrit value by more than 1,5 times the tolerance according to Table 1. After this test, a sieve is considered as not suitable if the sum of the residues on the 1 st , 2 nd , and 3 rd or on the 1 st , 2 nd , 3 rd and 4 th sieve respectively exceeds the permissible deviations of Table 1 by more than half the value.
The sieves marked with 3,35 mm, 2,36 mm and 53 μm shall be tested in accordance with ISO 3310‑1.