Before starting any carpentry project, check your table saw blade for alignment so that you can be sure that your cuts will be straight and plumb.
There are two measurements needed to determine the alignment of the table saw blade. These include run out, blade parallel and rip fence parallel alignment.
Step 1 - Run Out Alignment Test
Set the dial indicator on one edge of the blade, just inside the gullets, and then set the dial at zero. Turn the blade with a piece of wood through several revolutions and check the maximum variance indicated with each revolution. Make sure that you do not accidentally apply side pressure to the blade, which will make the readings worthless.
If the test shows run out, then remove the blade and clean the washer and the blade assembly. Small amounts of debris and sawdust can cause the blade to be out of alignment. Once you have the blade and assembly cleaned, then retest for run out.
If you continue to see run out, then look at the arbor to see if it is bent at all. Inspect the washers to detect if they have been damaged. If you do not see any damage with the arbor or washers, then remove the blade and install another one and try the run out test again.
Step 2 - Blade Parallel Test
Mark a point at one of the gullets that is close to you. Place the dial indicator at that point and zero the dial out. Turn the blade so that it is at the opposite side of the table and move the indicator to the same mark in the new position. The dial reading will indicate if your blade is out of parallel.
To correct a blade that it out of parallel, locate the bolts that hold the arbor assembly to the table. Usually these are located on the underside of the table. Loosen the bolts and move the assembly to align the blade to the miter slot. Retighten the bolts and retest the blade parallel.
Step 3 - Rip Fence Parallel Test
Insert the jig in the miter slot located near the front edge of the table. Move the rip fence until it presses the indicator plunger half way. Lock the fence down into position. Hold the indicator jig in place and zero the dial. Slide the indicator half the length of the rip fence and mark the reading at the far end.
If the rip fence is out of alignment, then clean away any debris or sawdust that might have accumulated, as this can result in misalignment. You will need to remove the clamping mechanism and mounting rail to clean away debris. Reassemble the clamping mechanism and mounting rail after cleaning the rip fence, retest the alignment.
If you are doing a great deal of work or using the rip fence frequently, you will need to check the alignment of the rip fence frequently to ensure that it is correctly and accurately aligned. This is particularly important because of the safety factor and potential for dangerous accidents if the rip fence is misaligned.