2.2.1 Methods of Assessing Straightness
2.2.1.1 Preferred method
The bar shall be supported on a suitable surface so as to eliminate or minimise sagging.
A 1 m long straight edge shall be placed on the surface of the bar at any position along its length. No part of the straight edge shall be within 150mm of the ends of the bar.
Straightness shall be determined by measuring the maximum gap between the bar and the straight edge by suitable means e.g. feeler gauge. The bar shall be deemed straight where the maximum gap does not exceed the values specified in 2.2.
2.2.1.2 Alternative method for round bars
The round bar shall be supported on a sufficient number of centres placed 1 m apart.
Straightness shall be measured by means of a suitable dial or indicator gauge placed at any position between the supporting centres.
The bar shall be deemed to be straight when rotating the bar through 360° the indicated reading (TIR) is not greater than twice the deviation specified in 2.2.
Note: Calculation of straightness for non standard length is based on the formula:-
(Non-Standard length)2 x Tolerance
(Standard length)2
1 in 1000 = 9mm maximim deviation in a 3000mm bar
Straightness is a perishable commodity and care in handling is required - particularly in small section sizes of high width to thickness ratios.
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