|The sine bar is used for accurately setting up angles for inspection or machining. It's really very easy to use and extremely accurate. |
The sine bar consists of a bar or plate with two rolls at either end. The center distance (C) of the rolls are usually 3, 5, or 10 inches on commonly available bars, but the rule works with any distance. When you place one roll at a specific height (G) the top of the bar will be at a specific angle (A). To get the specific height it's called "Building the Stack" because it's usually done by stacking gauge blocks.
The Sine Bar Rule: A(sine) X C = G
The sine of the desired angle (A) X Center-to-Center distance of the sine bar rolls (C) = Height of the Stack (G)
Example: We want to set our 5" sine bar for an angle of 18 degrees.
Sine of 18 degree angle* = 0.309
Center Distance = 5"
0.309 X 5 = 1.545
So we build our stack height (G) 1.545"
*(To find the sine of any whole angle from 1 to 90 degrees, use the Shopdawg.com Trig Table)