The old BS970 Parts 1 & 3:1991 standards have been replaced by a number of EN Standards, the most important of which are shown below.
- CN10088-3 Replaces BS970 Part 1: 1991 & BS970 Part 3: 1991 covering chemical composition & mechanical properties.
- CN10058 Tolerances for Hot Rolled Flat Bars CN10059 Tolerances for Hot Rolled Square Bars EN10060 Tolerances for Hot Rolled Round Bars CN10061 Tolerances for Hot Rolled Hexagonal Bars.
- CN10278 Tolerances for Bright Bars (Drawn, Turned or Ground).
- ISO186 Parts 1 & 2 Tolerance Classifications.
Diameter Tolerances
Smooth Turned
| Diameter (mm) | Tolerance (mm) |
| 18 to 30 | +0/-0.084 |
| 31 to 50 | +0/-0.100 |
| 51 to 79 | +0/-0.120 |
(These are H10 tolerances, which are ‘all minus’ tolerances)
Rough Turned
| Diameter (mm) | Tolerance (mm) |
| 75 to 150 | -0/+1.50 |
| 151 to 225 | -0/+2.00 |
| 226 to 410 | -0/+3.00 |
(These are ‘all plus’ tolerances)
Bright Drawn
| Diameter (mm) | Tolerance (mm) |
| 6 to 10 | +0/-0.036 |
| 11 to 18 | +0/-0.043 |
| 19 to 30 | +0/-0.052 |
These are H9 Tolerances
H9 Tolerances are ‘all minus’ tolerances: +0mm/- Figure in table
Width & Thickness Tolerances
Hot Rolled Square - Width & Thickness
| Size (mm) | Tolerance (mm) +/- |
| 75 to 150 | 1.50 |
| 151 to 225 | 2.00 |
| 226 to 410 | 3.00 |
Hot Rolled Flat - Thickness
| Size (mm) | Tolerance (mm) +/- |
| Up to 20 | 0.50 |
| 20 to 40 | 1.00 |
| 40 to 80 | 1.50 |
Hot Rolled Flat - Width
| Size (mm) | Tolerance (mm) +/- |
| 10 to 40 | 0.75 |
| 40 to 80 | 1.00 |
| 80 to 100 | 1.50 |
| 100 to 120 | 2.00 |
| 120 to 150 | 2.50 |
Angle Bars
Leg Length
| Leg (mm) | Leg Length Tolerance (mm) +/- | Thickness (mm) +/- |
| 20 | 1.50 | 0.40 |
| 25 | 1.50 | 0.50 |
| 30 | 2.00 | 0.50 |
| 40，50 | 2.00 | 0.60 |
| 60，70，80，90，100 | 3.00 | 0.75 |
Internal Radius
| Leg (mm) | Maximum Internal Radius (mm) |
| 20，25，30 | 4 |
| 40 | 5 |
| 50，60 | 7 |
| 65，70，75，80 | 9 |
| 90，100 | 10 |
ISO 286 Tolerances (in mm)
EXAMPLES:
- H = All Minus Tolerance e.g. 45mm dia. H9 = +0 / -0.062
- J = Tolerance Divided e.g. 45mm dia. J9 = +/- 0.031
- K = All Plus Tolerance e.g. 45mm dia. K9 = +0.062/ -0 (The K tolerance is usually only applied to larger diameter bars - over 75mm)
H8 = Precision Ground
H9 = Bright Drawn
H10 = Smooth Turned
Tolerance (mm) for Given Tolerance Number
| Diameter (mm) | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
| >1 ≤ 3 | 0.007 | 0.009 | 0.014 | 0.025 | 0.040 | 0.040 | 0.090 | 0.140 |
| >3 ≤ 6 | 0.008 | 0.012 | 0.018 | 0.030 | 0.048 | 0.048 | 0.120 | 0.180 |
| >6 ≤ 10 | 0.009 | 0.015 | 0.022 | 0.036 | 0.058 | 0.090 | 0.150 | 0.220 |
| >10 ≤ 18 | 0.011 | 0.018 | 0.027 | 0.043 | 0.070 | 1.110 | 0.180 | 0.270 |
| >18 ≤ 30 | 0.013 | 0.021 | 0.033 | 0.052 | 0.084 | 0.130 | 0.210 | 0.330 |
| >30 ≤ 50 | 0.016 | 0.025 | 0.039 | 0.062 | 0.100 | 0.160 | 0.250 | 0.390 |
| >50 ≤ 80 | 0.019 | 0.046 | 0.074 | 0.120 | 0.190 | 0.300 | 0.460 | |
| >80 ≤ 120 | 0.022 | 0.087 | 0.140 | 0.220 | 0.350 | 0.540 | ||
| >120 ≤ 180 | 0.025 | 0.100 | 0.160 | 0.250 | 0.400 | 0.630 | ||
| >180 ≤ 250 | 0.115 | 0.185 | 0.290 | 0.460 | 0.720 | |||
| >250 ≤ 315 | 0.320 | 0.520 | 0.810 | |||||
| >315 ≤ 400 | 0.360 | 0.570 | 0.890 | |||||
| >400 ≤ 500 | 0.400 | 0.630 | 0.970 | |||||
| >500 | 0.440 | 0.700 | 1.100 |
Straightness Tolerances for Bright Bars
Taken from BS EN 10278:1999, applicable to Bright Bars only.
Method of measuring deviation - Preferred Method B.1 from BS EN 10278:
- The bar shall be supported on a suitable surface so as to eliminate or minimise sagging.
- A 1 metre long straight edge shall be placed on the surface of the bar at any position along it’s length. No part of the straight edge shall be within 150mm of the ends of the bar.
- Straightness shall be determined by measuring the gap between the bar and the straight edge by suitable means such as a feeler gauge.
Deviation from Straightness
| Product | Dimension | Maximum Deviation (mm) Within a 1m Length Measured at Least 150mm from Either End of Bar |
| Round | 1.0mm | |
| Square & Hexagon | ≤75mm | 1.0mm |
| Square & Hexagon | >75mm | 1.5mm |
| Flat | Width <120mm | On Width: 1.5mm |
| Flat | Width <120mm | On Thickness: 2.0mm |
| Flat | Width ≥120mm | On Width: 2.0mm |
| Flat | Width/Thickness <10.1 | On Thickness: 2.5mm |
| Flat | Width ≥120mm | On Width: 2.500 |
