I got this tool last year as a freebie when I made an order from Rockler, and I just tossed it in my router table and promptly forgot about it.
But now that I needed to do some precision router table work, I finally got a chance to use it, and so I’ll give a bit of a review. Though I’m sure there are other examples of the same concept, this one can be gotten from Rockler for $5.99.
Though they illustrate the gauge being used directly on the router, it is also useful for measuring the height of bits as they protrude from a router table
Deceptively simple in construction, the aluminium is sturdy and can stand unsupported on its “feet”. I keep the bit low, slide the gauge over the bit, and raise the router until the gauge moves. If you can slide the gauge side-to-side over the bit, you have to raise it some more… but once it touches you back off a fraction.
You can also use this tool to measure table saw blade heights, but you have to make sure you are measuring at the peak of the highest tooth, or your depths will not be accurate.
The gauge can measure from 1/16” to 1-1/2” in 1/16” increments, so unless you are working with smaller increments, this tool should be adequate.
Overall, for a tool that costs less than a board-foot of maple, you can’t really go wrong!
-- Dekker - http://www.WoodworkDetails.com/