Sine bar

The dimension between the two rollers is chosen to be a whole number (for ease of later calculations) and forms the hypotenuse of a triangle when in use.

If one roller is raised by a known distance, usually using gauge blocks, then the top edge of the bar will be tilted by the same amount forming an angle that may be calculated by the application of the sine rule.

At this position, the top surface of the sine bar is inclined the same amount as the wedge.

The sine of the angle of inclination of the wedge is the ratio of the height of the gauge blocks used and the distance between the centers of the cylinders.

In the advanced type some holes are drilled in the body of the bar to reduce the weight and facilitate handling.

Sine bar set up with one end raised on a stack of gauge blocks
Trigonometric triangle with sides. The opposite side is perpendicular relative to AC axis.
10-inch and 100-millimetre sine bars. In the U.S., 5-inch sine bars are the most common size. [ 1 ]