I wasn't thinking about using multiple scales just trying to decide if one scale, on one of my marking devises, might in some instances be useful and eliminate the need for other measuring tools.
It could be useful in some instances. The best way to put the question to rest would be to acquire one and find out.
On the Tite-MarkŪ gauge, the threads are 20 per inch. That means a full turn of the adjuster moves the blade 0.05". Half revolution and quarter revolution adjustments would be 0.025" and 0.0125" respectively. Pretty soon one gets a feel for the adjustment without a scale.
With a good scale, if one was looking for center, it might speed the ability to hit it right on. Measure with the gauge, set to center test and most likely if there was an adjustment it would be rather slight.
Another thing that helps me measure in the shop is a bunch of wood pieces of various known sizes. They can be used like feeler gauges. They are very helpful when setting up things like the fence on a rabbet or plow plane. They can be used for checking depths of shoulders on M&T or lap joints. Chisels can also be used as a verification gauge.
Most of my actual measuring is done with an old four fold rule or a tape measure. It used to be a struggle to measure and make everything with gnat's eyelash accuracy. Now my work is easier with measuring or comparing to make the pieces fit together.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)