BS 6740:1987

This standard BS 6740:1987 Method for determining departures from roundness by measuring variations in radius is classified in these ICS categories:

• 17.040.30 Measuring instruments

This International Standard specifies a method for determining departures from roundness by measuring variations in radius by means of contact (stylus) instruments.

It establishes

1. types of instruments and gener requirements;
2. recommendations for the use of instrument
3. procedures for calibration of instruments a verification of their characteristics.

This International Standard applies to the assessment of the departures from ideal roundness of a workpiece through the medium of a profile transformation, obtained under reference conditions, expressed with respect to any one of the following centres:

1. centre of the least squares circl
2. centre of the minimum zone circl
3. centre of the minimum circumscribed circl
4. centre of the maximum inscribed circl

Each of these centres may have its own particular application. The position of the least squares centre can be calculated from a simple explicit equation given in Annex F.

Departures from roundness of the measured profile, procedure, calibration and determination of systematic errors of rotation are dealt with in Annex A to Annex D, respectively. Annex E gives rules for plotting and reading polar graphs.

NOTE 1 Profile transformation is defined in ISO 6318.

NOTE 2 Reference conditions include the stylus, frequency limitations of an electric wave filter (if used), permissible eccentricity of the graphical or digital representation of the profile (generally 7 % to 15 % of its mean radius, see Annex E), the position of the measured section or sections relative to some feature of the workpiece.

Uses contact (stylus) instruments.