Tolerances to BS EN 10278 for bright stainless steel bars

Introduction

Tolerances for bright drawn, ground, turned and polished stainless steel bars are included with the general standards for other bright steel bars in BS EN 10278.
The standard mentions the shapes round, hexagon, square and flat, but not all of these cross sections have specific tolerance tables. This article will only show the tolerances for stainless steel bars for the sections specifically covered. All dimensions are in millimetres (mm).
The data given is not intended to replace that shown in individual standards to which reference should always be made.
Dimensions and tolerances for stainless steel long products are covered in more detail in the BSSA special report 'A Specifiers Guide to the New EN Standards for Stainless Steel Long Products' available in the publications area of the web site.
These tolerances can be used in conjunction with bars specified to BS EN 10088-3

Finish condition and tolerance classes

Finish condition

BS EN 10278 has the symbols for finishes, as shown below.
drawn +C
turned +SH
ground +SL
polished +PL

Tolerances classes

Tolerances on dimensions (diameter, thickness, width) are those established by ISO 286-2. The tolerance classes that are applicable to various finish conditions and sections are shown in the table below.

Finish condition Tolerance class to ISO 286-2
h6 h7 h8 h9 h10 h11 h12
Drawn - - -R R R,S,H R,S,H
Turned - -- R R R R
Ground R R R R R R R
Polished R R R R R R R

R = round; S = square; H = hexagon
The tolerances (or limit deviations) for the whole range tolerance "ISO" classes covering round and hexagon bars is shown in table below. The ranges are all +0, all minus ie for a 20mm bar to tolerance class h9 with a tolerance range of 0.052, the tolerance is -0.052/+0, giving an acceptable product size range of 19.948 to 20.000mm.

Tolerances on cross sections

Drawn round, hexagon and square bars

Drawn round bars are covered by class h10, except for any supplied in the quenched and tempered condition (ie martensitic stainless grades), which are covered by class h11
Hexagon and square bars are covered by class h11 in sections sizes up to 80mm and class h12 in section sizes over 80mm. Ground finished products are covered by class h9.

Nominal dimension Tolerance class to ISO 286-2
h6 h7 h8 h9 h10 h11 h12
over 1 up to 3 0.006 0.010 0.014 0.025 0.040 0.060 0.100
over 3 up to 6 0.008 0.012 0.018 0.030 0.048 0.075 0.120
over 6 up to 10 0.009 0.015 0.022 0.036 0.058 0.090 0.150
over 10 up to 18 0.011 0.018 0.027 0.043 0.070 0.110 0.180
over 18 up to 30 0.013 0.021 0.033 0.052 0.084 0.130 0.210
over 30 up to 50 0.016 0.025 0.039 0.062 0.100 0.160 0.250
over 50 up to 80 0.019 0.030 0.046 0.074 0.120 0.190 0.300
over 80 up to 120 0.022 0.035 0.054 0.087 0.140 0.220 0.350
over 120 up to 180 0.025 0.040 0.063 0.100 0.160 0.250 0.400
over 180 up to 200 0.029 0.046 0.072 0.115 0.185 0.290 0.460

Out of round (ovality)

The standard states that the maximum deviation from "out of round" shall not be more than half the specified tolerance but never above the upper limit of the tolerance.

Flat bars

Drawn flat bars are covered in table 3 of the standard and are shown in the tables below.

Width Deviation ISO 286-2 class
Up to 18 +0 -0.11 h11
over 18 up to 30 +0 -0.13 h11
over 30 up to 50 +0 -0.16 h11
over 50 up to 80 +0 -0.19 h11
over 80 up to 100 +0 -0.22 h11
over 100 up to 150 +0.50 -0.50 -
over 150 up to 200 +1.00 -1.00 -
over 200 up to 300 +2.00 -2.00 -
over 300 up to 400 +2.50 -2.50 -

Thickness Deviation ISO 286-2 class
over 3 up to 6 -0.075 h11
over 6 up to 10 -0.090 h11
over 10 up to 18 -0.11 h11
over 18 up to 30 -0.13 h11
over 30 up to 50 -0.16 h11
over 50 up to 60 -0.19 h11
over 60 up to 80 -0.30 h12
over 80 up to 100 -0.35 h12

Note
All deviations on thickness are +0. These deviations only apply to steels with carbon contents up to 0.20%. Over this limit the deviation is increased by 50%.

Tolerances on length

BS EN 10278 specifies the types of length and length tolerances in the format of the following table.

Type of length Length Limit deviation To be stated on order
Manufacturing length 3000 to 9000 +/- 500 Length
Stock length 3000 or 6000 0, +200 eg 6000
Cut to length Up to 9000 To specifications with +/- 5 minimum Length and tolerance

Note
The standard to be consulted for notes on short length bars.

Tolerances on straightness

The standard covers covers both stainless and non-stainless steel families. Only the tolerances relating to stainless steels are shown in the following table.

Product form Nominal dimension Deviation
Rounds -1.0
Squares and hexagons up to 75 1.0
over 75 1.5
Flats width below 120 1.5 on width / 2.0 on thickness
width at or over 120 and w/t below 10:1 2.0 on width / 2.5 on thickness
width at and over 120 and w/t at or over 10:1 2.5 on width / 3.0 on thickness

Methods of measurement

Except for straightness, BS EN 10278 does not provide guidance on the measurement of the specified dimensions and how to verify whether or not the tolerance limits have been met.

Straightness

The standard outlines two methods for measuring straightness.
The preferred method involves supporting the bar on a suitable surface to eliminate or minimise sagging. If a 1 metre long straight edge is placed on the bar at any position, then the maximum gap between the bar and straight edge is measured by a suitable means such as inserting feeler gauges. The bar is deemed straight if the gap is less than that shown in the table in the 'Tolerances on straightness' section, above.
The standard also describes a dial gauge method as an alternative to the gap measurement method.

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