Checking a Miter Gauge for Squareness
Here’s a simple way to find out if your tablesaw miter gauge makes a square cut. Place the gauge as close as possible to the front edge of the saw table. Select a piece of plywood or other scrap sheet-stock that is about as long as the distance between the miter gauge and the sawblade — the longer the better. The plywood should be wide enough to hold tightly to the gauge, roughly 1 ft. A nonslip surface (sandpaper) on the face of the miter gauge is helpful. One edge of the plywood needs be straight and true — mark it as the true edge. Hold the true edge against the miter gauge and cut about 1/8 in. off one side of the plywood. Flip the board over so that the true edge is still against the miter gauge and cut 1/8 in. off the opposite side in the same manner.
Now measure both ends of the board. If the miter gauge is square to the blade, both ends of the plywood will be equal. If the gauge is not square, the measurements will be different. The best part of this procedure is that any error will be doubly magnified. For example, a difference of 1/64 in. will show up as 1/32 in. Adjust the angle of the miter gauge accordingly and recut.
Fine Woodworking #184