The deviation from the straight line of a tube length in mm per meter applies as measure of straightness for tubes. Tubes should be aligned straight according to the eye; complete straightness cannot be guaranteed. Special requirements have to be agreed, if applicable. For precision steel tubes with a diameter over 15 mm, according to DIN 2391, 2393 and 2394, 0.25 % of the gage length and for grades with yield stresses over 500 N/mm², 0.30 % of the gage length are valid. Requirements to straightness are determined in the dimension standards or are agreed especially. Mostly they can be fulfilled by special straightening only.

1. Parallelism to required line of travel (e.g. haunches neither left nor right of centerline) 2. Alignment of body parts appropriate to the task at hand (e.g. not a popped shoulder or twisted neck). 3. Directness of line of travel (e.g. not weaving).

The condition where an axis is a straight line (or, in the case of a centerplane, each line element is a straight line).

A term that refers to the deviation of the cast axis from the true axis.

This is when the spine is parallel to the straight line or long side of the mÈnage.

A deviation from a line of sight which is generated by a reflected light–as for example, an autocollimator and mirror.

A measured characteristic for quality; any deviation from the shortest distance between two points. Straightness is often confused with parallelism.

Description of the shortest line between two points, often confused with parallelism.

(n) A form control for geometric dimensioning and tolerancing. Straightness means that all points on a part have the same direction throughout its length. Straightness also refers to the path describing the shortest (uniform) path between two points.