I used my new thickness gauge today and measured the top, before starting any graduating. I am using the (new) Siminoff book as a general reference for building the instrument. Therefore, I took the same measurements that Siminoff illustrates on the blueprints. I expected them to be off and then make adjustments. However, the mandolin top is thinner, in general, then the Siminoff spec. I've heard the same from other IV kit builders and so I wasn't quite surprised. However, I am paying attention to the min thickness, which is in the recurve area. The min thickness of the top piece is measuring around .12", before any carving or sanding. Siminoff says .12 is good for wood that's 14 grain lines inch or more. He also says that you can go down to .110 if the wood has more than 14 lines/inch. The top of my mandolin has uneven grain lines, being most sparse at the center and getting denser as you get to the edges. In the min area, the line density is close to 18/inch. I suppose that that's good if I'm going to end up with or even less after final shaping and sanding.
Since there is no way for me to match the Siminoff spec, the best I can do is try to make the thickness as even as I can around the plate, so that it vibrates evenly all the way around, and put in a small recurve close to the edge.
Note: Since the gauge has round surfaces (where it meets the mandolin plate) and since the plate itself is curved, you can get various readings depending on how the plate is angled. The correct (and most sonsistent) measurement is the one that gives you the min reading.
