Table Saw Alignment

What

The bearings on a Table Saw arbor are designed to allow it to rotate freely but not move side to side.  As bearings wear, this side play becomes more pronounced and will cause vibration.

Why

Side play can affect the accuracy and reliability of meansurements needed to align the blade.  Vibration from side play will produce a poor quality cut which will need further work (jointing) before glue-up.  When the arbor bearings are in good shape, a well aligned saw with a high quality blade can produce an edge that is ready for glue-up without any further preparation. 

How

Place the stylus of the dial indicator against the surface of the blade as shown in the photo above.  The dial indicator is shown with an Offset Bar on the end of the plunger.  This isn’t necessary, you can place the stylus anywhere on the surface of the blade plate.  It doesn’t need to be near the table surface.   Next, rotate the scale so that the large hand points to zero.  Pressing on the sides of the blade will cause the reading to change.  Basically, you are measuring how far the blade flexes as you press against it.  Ideally, the reading should return to zero when you release the pressure.  If it doesn’t, then you are measuring the amount of side play in the bearings.  If it’s less than 0.001″ (one thousandth of an inch, one graduation on the dial), then there’s nothing to worry about.  If it’s more than 0.001″ but less than 0.005″ then you’ll want to make note of it for future measurements (this play will influence the accuracy of your alignment).  If it’s more than 0.005″, then you should replace the bearings (or forget about using this table saw for accurate work).

Ed Bennett
ejb@tablesawalignment.com