Neeed to calibrate bevel stop on dewalt 708 compund miter saw. at zero degrees (or 90 really) it is out of square a half degree.

I assume you can find the adjusting screws, but here's how to measure if you have it dead-on: First, confirm repeatability as follows----. Move the saw as if you were going to cut at miter, then move it back to zero. Now cut off the end of a 6 inch (or so) board. Then move the saw again, and move it back to zero. Cut off about 3/4 inch of the same board (make sure you haven't turned the board over). The 3/4 inch piece you have cut off might not be square, but the two cut edges of the 3/4 inch piece should be exactly parallel to each other. Find a way to confirm that. A micrometer or good calipers make this easy, but you may have to improvise - the key is that your check for parallel needs to be more precise than measuring it with eyeballs and a tape measure. Repeat this a couple of times. You may find that you have to be careful about resetting the saw each time so that you can get repeatability. OK, now that you have a repeatable setting turn the board over and take another cut. Any deviation from 0 (or 90) will be doubled and the two cuts will not be parallel. Make your adjustments to the saw until you get two parallel cuts when you flip the board over. And one more thing! This method ASSUMES that the board you are cutting has parallel edges. If you have calipers this is easy to confirm.