Chris,

What is important to scoring is the remaining thickness of board material.
The problem that typically arises is that the scoring requirement gives a
depth to the scoring. Using standard board thickness tolerances, results in a
variation of the remaining material, to the extent of being too robust. 

The proper method is to specify the remaining thickness requirement. The
board fabricator will then compensate his cut, for the overall thickness of
the finished board. 

You can take advantage of this method in your incoming inspection. Just
measure the overall finished board thickness and subtract you groove depth
measurements. The result will be the remaining board material.

There are a number of suppliers of gages, specifically designed to measure
groove depth.

Regards,

Gary Ferrari
Tech Circuits
(203)269-3311