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.
Step 2: Loosen the mounting bolts
Under the aluminum disc inside the column are two bolts. The heads are 9/16". With a wrench you are to loosen them just a little.
Step 3: Bump the arm
After the bolts inside the column have been loosened a little, you are to bump the saw's arm a little and check the blade travel with the square again. When the arm is square to the fence, you are to tighten the bolts inside the column. Put the aluminum disc back in place and everything should be good again.
But, it is very difficult to bump the arm without bumping it either too much or too little. There is a much easier way.
Step 4: Adjust the table with precision
There is an easy way to move the table rather than the arm and move it just a little so the edge of the table that holds the fence in place is exactly 90 degrees away from the blade's travel on the arm.