This is my 10" Craftsman Radial Arm Saw, 1972 vintage. It is very important that the arm is exactly 90 degrees to the fence at the back of the saw table. Note the square. Pull the motor along its travel and see if the blade teeth follow the edge of the square exactly. It is quite common that a gap between the blade teeth and the square of a few thousandths of an inch will form as the saw moves back toward the end of the arm. This will cause inaccuracies in any precision cutting. The owner's manual gives a recommended procedure for aligning the saw, but it is difficult and does not work well. This Instructable will show you a much easier, much more precise way.
Step 1: The factory recommended procedure
The recommended procedure involves loosening and moving the arm in its mount. Remove the two screws on the angle scale at the top of the column and remove the aluminum disc on which the angle scale is printed.