Have you ever tested the five step proces on your table saw,To Check your 90° Mitre?

[johnny means]

I use the 5 cut method for squaring anything that cuts over a few inches. It can be as accurate as you want it to be. I could easily get my slider to within a 64th over 10 ft. That's probably within the margin of error you'd see on any human powered cut.

[Steve Demuth]

The five cut method has the advantage that it will work without the need for accurately parallel sides on your test piece. But if you can manage those (which shouldn't be hard if you're squaring a miter gauge or crosscut sled on an otherwise properly set up table saw), you can achieve the the same results with a single cut, a feeler gauge, and no measurement - in about the 1/3 the time. Cut your test piece with parallel faces 5" wide and long enough to register against most or all of your fence. Make your test cut through the center. Flip the right end and butt the pieces together. Use a feeler gauge to measure any gap. Then use the feeler gauge to move the fence in the direction of the open end of the butt joint at a point 10" from the pivot of the fence. If 5" and 10" don't strike you as a long enough throw to get the angular resolution you want, go with 10" and 20"

Yes, the 5-cut method gives you a 4X multiplier of any out-of square, and this method only gives a 2X. Not an issue, since you can do this entirely with the feeler as a reference, 2X will get you just as good a result as the 4X of the five-cut method. You can easily get within .002" over 10" if you use a suitably hard, stable test piece and your crosscut blade is really sharp, and your miter gauge or sled runners run that snuggly in the miter slots.

If you don't have a feeler gauge, you can get within a few thousandths just by eyeball with this method. For nearly all woodworking tasks, that will suffice.

[Simon MacGowen]

For nearly all woodworking tasks, that will suffice.

That is the key here. A lot of products are sold for big bucks because of people's obsession with machinist's standards.

I have visited some of the well-known as well as unknown woodworkers who produced or produce top quality pieces and their set ups are like yours and mine: machines tuned to tolerances offered by the suppliers, or outside in a few cases.

Simon