"Lew Hodgett" writes:

Since most of the above applies to metal working machinery, how does
it transfer to wood working tolerances?

I'm not a big tolerance proponent, but making something like a 12" by
12" by 12" box with 1/8th" thickness required careful tolerances.
That's because small errors accumulate over distance and over cobined
angles.

I have a few combination squares. I bought a Starrett off eBay at a
good price. (I actually bought pieces separately - cheaper than buying
a set.) Note that there are two kinds of heads - hardened or not.
One has a pebbled finshish, and the other is smoother.

The Starrett, even though it's old and has a patina, is still very
readable. I have a Lufkin and Stanley rule one that has some slight
rust, and the readability of the Starrett is much nicer. It's brighter
and easier to read in dim light. There is not as much tarnish on
it. Perhaps it's the hardened blade. Also - the little pin you use to
scribe has a nice solid feel to it, compared to the other two combo
squares I have.

There's a certain joy in using a Starrett.

One of these days I'm going to get a 4" or 6" double square Starrett.
I like the Lee Valley DS ($20 on sale) very much, but one of these days....