I wouldn't trust a store bought factory edge. It's good enough for
building construction but often not good enough for precision work. It
depends on the factory.
A quality panel saw or high quality slide on a cabinet saw will get you
the best rip for lengths over 4'.
Thin blades can wobble at high speed, especially when hot from cutting
friction and under variable load, knots, grain alignment, etc.. Use
dampeners when using thin blades. I can measure the difference of the
kerf with and without dampeners.
A table cannot be trusted to remain in alignment if there is any
movement; play in the bearings, warped blades, loose top, etc..
Given that the table saw is of quality construction, all bearings, arbor,
blade, trunnions, etc. are in good condition and all bolts are tight, the
saw could still be out of alignment but in a fixed stable amount.
Parallelism of blade to miter slots and a true 90deg stop are the most
common problems I've seen on "good" tables saws. These are often bad in
store demo units and even at many commercial shops. Many people (or just
me) adjust the 90deg stop past 90deg and use a guide to manually set
rather than relying on the stop. If angles are cut often, better results
can be had by hand setting the angle vs. using the saw angle ticks. These
are just used as a rough first position to start blade alignment.
I don't use a parallel fence to avoid kickback so I don't count bad fence
alignment as an issue. The fence must be set and checked manually for
every critical cut. A good fence system should stay within a few
hundredths of an inch between position changes without manually checking
Positioning is very stable on my Unisaw. I don't have a reference surface
long enough to verify long cuts. Measuring long cuts appear to be <0.01".
Well within 0.003" for 12" or less. The majority of what I cut is very
small. I have only fully aligned it twice, once on purchase and once
after a "bumpy" shop relocation. It needed it both times. I have
purchased blades that were slightly warped, these go on the radial or
There are many variables when cutting; feed speed, stalling in the blade,
smoothness of sliding table or wood against top surface, knots, grain,
splits. Once the cut goes off the saw's main top surface (>3'), movement
and deviation of the cut is common.
After alignment cut 10 pieces 2' in length and if you can't get more than
7 pieces within 0.01" of each other the saw may have alignment stability
problems, play in the bearings, warped blades, etc..
Remember that you can easily push more than 0.005" out of alignment by
sloppy cutting methods on a well tune saw. At it's best, it can only ever
be as precise as you are when cutting.
Also if you do anything else to the cut edge, plane, scrape or sand, a
few thousands off to start won't really matter. Long sanded edges will
often be much worse than .005" deviation.
Theoretically a slow start motor without the startup torque could keep
alignment longer on flimsier built saws. Although high end shops I've
been to don't use them on saws over 3hp.
Short answer: Most books and manuals I've read state 0.003"-0.005".