All I do is just make sure that they are basically level. I generally don't
tie down the floor models as sometimes I need to move them about to handle
really large pieces.
If you want to be dedicated to the job, level the base and tie it to the
floor if you want to. I really haven't even seen anybody else do that in
the various places that I have worked and and some of those places did some
fine work.
Table models I'd tie to the table just to make sure that it doesn't walk
about as those mills are a lot lighter and heavy work may cause the mill to
walk about on the table.

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Why isn't there an Ozone Hole at the NORTH Pole?