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Tolerances for Metric O-Rings

Due to the fact that there are literally dozens of O-Ring standards globally, finding a single recognized standard for metric O-Rings is virtually impossible. After extensive research, RT Dygert has adopted tolerances based on ISO 3601-1, Class B, Annex A.4. The table below illustrates a few examples of tolerances using this standard. Sizes not shown can be calculated using the following formula. 

Tolerance = ± [(Inside Diameter0.93 x 0.009) + 0.11]  

CROSS SECTION TOLERANCES (mm)
0.00 to 2.25 ± 0.08
2.26 to 3.15 ± 0.09
3.16 to 4.50 ± 0.10
4.51 to 6.30 ± 0.13
6.31 to 8.40 ± 0.15

Inside Diameter Tolerances (mm)
I.D. Tol. ±
5.00 0.15
10.00 0.19
20.00 0.26
40.00 0.41
80.00 0.69
160.00 1.23
320.00 2.27
640.00 4.28