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Tolerance

Metric Tolerances

mm H11 H10 H9 H8 H7
> 1 to 3 0.060 0.040 0.025 0.014 0.010
> 3 to 6 0.075 0.048 0.030 0.018 0.012
> 6 to 10 0.090 0.058 0.036 0.022 0.015
> 10 to 18 0.110 0.070 0.043 0.027 0.018
> 18 to 30 0.130 0.084 0.052 0.033 0.021
> 30 to 50 0.160 0.100 0.062 0.039 0.025
> 50 to 80 0.190 0.120 0.074 0.046 0.030
> 80 to 120 0.220 0.140 0.087 0.054 0.035
> 120 to 180 0.250 0.160 0.100 0.063 0.040

Inch Tolerances (Nominal Sizes)

inch H11 H10 H9 H8 H7
> 3/64 to 1/8 0.00240 0.00157 0.00098 0.00055 0.00039
> 1/8 to 15/64 0.00295 0.00189 0.00118 0.00071 0.00047
> 15/64 to 25/64 0.00354 0.00228 0.00142 0.00087 0.00059
> 25/64 to 45/64 0.00433 0.00275 0.00169 0.00106 0.00071
> 45/64 to 1 3/16 0.00511 0.00331 0.00205 0.00130 0.00082
> 1 3/16 to 2 0.00629 0.00393 0.00244 0.00153 0.00098
> 2 to 3 1/8 0.00748 0.00474 0.00291 0.00181 0.00118
> 3 1/8 to 4 3/4 0.00866 0.00551 0.00342 0.00213 0.00137
> 4 3/4 to 7 3/32 0.00984 0.00629 0.00393 0.00248 0.00157

Tolerances for Cold Drawn Steel Bar to BS 970: Part 3: 1991

SECTION SIZE (mm) TOLERANCES (mm)
Round Diameter
618 + 0 – 0.070
> 18 30 + 0 – 0.085
> 30 50 + 0 – 0.100
> 50 80 + 0 – 0.120
> 80 100 + 0 – 0.140
Square & Hexagonal Across Flats
18 + 0 – 0.090
> 18 30 + 0 – 0.110
> 30 50 + 0 – 0.130
> 50 80 + 0 – 0.160
> 80 by arrangement
Flat Width
> 10 18 + 0 – 0.110
> 18 30 + 0 – 0.130
> 30 50 + 0 – 0.160
> 50 80 + 0 – 0.190
> 80 100 + 0 – 0.220
> 100 120 + 0 – 0.350
> 120 180 + 0 – 0.400
> 180 by arrangement
Flat Thickness
10 18 + 0 – 0.110
> 18 30 + 0 – 0.130
> 30 50 + 0 – 0.250
> 50 by arrangement

Tolerances should be used for guidance only, as these are conditional on the material being measured within the parameters specified by BS 970: Part 3: 1991. For Weights of Steel please refer to CONVERSION TABLES & FACTORS.