Machine Squaring: To square the machine you first need to cut a square and determine if it is square or skewed. If it is skewed, the machine is out of square. To square the machine you will loosen the belt tension on one side of the machine. With the tension loose on the belt, you can skip teeth on the timing belt to move this side of the gantry fore or aft depending on your test square.

Measure the cut square corner to corner or put a framing square on it to determine which direction to move the gantry side. Again, for coarse adjustment more than 1/16" - 1/8", loosen the timing belt tension and skip a tooth. For fine adjustment, loosen one side of the drive chain and tighten the other. For instance, loosen the rear chain bolt 1/2 turn and tighten the front bold 1/2 turn.

See the graphic examples below. The skew in these images is exaggerated for graphic purposes. You will not be able see the skew by eye.