What does a miter measure? (You think this is a trick question, right? Well, it’s not.) While a “true” miter might be that perfect 45 degrees, how many situations have you encountered where the “truth” is, shall we say, fudged a little bit – by your not-true-to-plumb walls, for example. And then what do you do to figure the correct angle for your miter cuts?
Enter the Miter Divider. An accessory from Arnott Tools, it works very similarly to that protractor you used in high school geometry class: put the Miter Divider up against the angle you’re working with. It will adjust so that the tool itself becomes the angle. You carry this carefully preserved angle to your piece of scrap wood; put a pencil in one of the guide holes and draw one line of the arc; place your pencil in the corresponding hole on the other side to draw the other side of the arc; then use the flat edge of the Miter Divider to draw a line where the two arcs intersect. Put that piece of scrap lumber in your saw and set the angle so that the saw cuts along the straight line you’ve drawn. Once you’ve tested the fit on the angle you’re working with, you’re ready to use that saw setting to cut that angle. Then you flip over one of the two pieces of scrap lumber, set the saw for the other angle of your miter, test the fit of that cut, and then make the second cut for your angle.
You’ve now cut a miter without measuring…even though the Miter Divider now does come with a built-in ruler, for those of you who like to keep track of the stats. It sells for about $20, with more information at http://www.miterdivider.com.