BS 3730-3:1982

Numerical assessment of departures from roundness by combinations of two- and three-point measurement. Applicable to internal and external diameters. Clauses deal with procedure, evaluation of measurement errors, measuring conditions.

This Part of this British Standard describes methods for the numerical assessment of departures from roundness by the combination of two- and three-point measurement. The following methods are dealt with:

1. determination by means of two-poi measurement (measurement of diameters);
2. determination by means of three-poi measurement, summit (symmetrical or asymmetrical setting);
3. determination by means of three-poi measurement, rider (symmetrical setting).

Any statement regarding an out-of-round section is incomplete unless the extent and nature of the departures from roundness is given and this is dealt with in Appendix A to D of BS 3730-2:1982.

For routine or in-process inspection, the requirements of BS 3730-2 may either be needlessly accurate or the items to be inspected may be too large to be accommodated.

The methods described in this Part of this standard may give faster and cheaper ways of assessing departures from roundness. This assessed value will deviate from the true value. The difference between the measured value and the true value can be estimated with help of Table 2 to Table 8, under the presumption that the undulation numbers are known and of sinusoidal nature. For non-sinusoidal undulations, a theory for estimating such deviations is not yet available.

NOTE The titles of the publications referred to in this standard are listed on the inside back cover.