What is BS 3730-3 - Two- and three-point measurement about?
BS 3730-3 is an International Standard that helps in assessing the departures from roundness.
BS 3730-3 describes methods for the numerical assessment of departures from roundness by the combination of two- and three-point measurements. The following methods are dealt with:
- Determination by means of two-point measurement (measurement of diameters)
- Determination by means of three-point measurement, summit (symmetrical or asymmetrical setting)
- Determination by means of three-point measurement, rider (symmetrical setting)
Who is BS 3730-3 - Two- and three-point measurement for?
BS 3730-3 on two- and three-point measurement is useful for:
- Manufacturers of stylus instruments
- Manufacturers and designers of coaxial anvils
- Mechanical engineers
- Testing authorities
- Quality assurance personnel
Why should you use BS 3730-3 - Two- and three-point measurement?
Two-point measurement is the measurement between coaxial anvils, one fixed and one moving in the direction of measurement. Three-point measurement is the measurement between anvils, two fixed and one moving in the direction of measurement.
BS 3730-3 assists with the measuring conditions and usage of the instrument. BS 3730-3 helps with the procedure to cover all forms of deviations and numbers of undulations at different angles between fixed anvils. BS 3730-3 describes the methods that give faster and cheaper ways of assessing departures from roundness. This assessed value deviates from the true value. BS 3730-3 helps in estimating the difference between the measured value and the true value estimated under the presumption so that the undulation numbers are known and of sinusoidal nature.
BS 3730-3 provides guidance on the method for determining departures from roundness two- and three-point measurement which is very helpful for the users of stylus instruments.  
