ABSTRACT
It is important to note that the scribed lines are only a guide, and any accurate dimension must be finally checked by measuring.
3.1 Datum The function of a datum is to establish a reference position from which all dimensions are taken and hence all measurements are made. The datum may be a point, an edge or a centre line, depending on the shape of the workpiece. For any plane surface, two datums are required to position a point and these are usually at right angles to each other.
