Maker's Name: 
Steven Painter
Where made: 
17.9 × 4.2 × 4.6 cm

A sine bar is used in engineering metrology in the accurate measurement and laying out of angles.

The bar has precision ground cylinders at each end and a precision straight section parallel to the line between their centres. It can serve as the hypotenuse of a triangle set up on a  surface plate with ( a stack of) gauge blocks making up the third side. Since the distance between the cylinders is accurately known, the sine of the angle is immediately given.

The holes in the bar are just to lighten it and to make it easier to handle. This example was made by the donor, Mr Painter, as an apprenticeship exercise. Think about the steps of measurement and machining that went into making it.