A mitre saw protractor works to accurately measure and provide users with angles. These angles can then be used in conjunction with a mitre saw to produce specific types of cuts for certain applications.
To measure an angle, the arms of the mitre saw protractor are opened to fit in or around the angle. The O-ring acts as a pivot allowing the arms to rotate to accommodate the angle you want to measure.
The mitre saw protractor arms are then placed in or around an angle.
When the arms rotate, the arrows on the scales will line up and point to the correct measurement. The scales on a mitre saw protractor are mitre and single cut scales.
A mitre cut angle would be the outer arrow pointing to the inner scale.
The inner scale of the protractor measures 0 to 90 degrees in both directions. The inner scale has a smaller measuring range than the outer scale because it halves the angle without the use of calculations, providing a mitre cut to form a mitre joint.
For example, 45 degrees on the inner scale would really be 90 degrees.
A single cut angle is the inner arrow pointing to the outer scale.
The outer scale measures 0 to 90 degrees in each direction.
This will show the actual measurement of a single cut angle as it would be shown on a mitre saw.
Whether the mitre saw protractor is upside down or backwards, both the inner and outer scales measure 0-90 degrees in each direction, so the arrows will always point to the correct reading.
Finally, you can adjust the settings on your mitre saw to correspond with the measured angles, so as to produce specific types of cuts.