Ah, there�s the rub. So often we see scoring requirements defined based on depth of cut. This ignores that the depth changes with a variety of factors, including: * Wear on the cutting blade. * Variation in thickness of the fabricated board.
So, controlling the web is really the issue. Web thickness should not vary with board thickness. Look at IPC-2222 - Sectional Design Standard For Printed Board For Organic Printed Boards, page 14 for specific recommendations. You can purchase it from IPC [www.ipc.org].
There are rcommendations of this and measuring the web in the fine SMTnet Archives.