graduation advice

**MinkBrookRambler** · Nov-02-2016, 4:09pm

I have a question about how to keep track of graduation lines as I work on the inside of my soundboard and backboard.

I'm using a graduation map that I have on paper, and I've got multiple photocopies. You can see the graduation map lightly pasted to the underside of the soundboard in the attached photo; I used it to drill to rough depth. I have the outside surfaces of each of the two plates to more or less finished contour dimensions, and I've hogged out the inside surfaces to within about a millimeter or so of my goal thickness. The drill holes are gone now.

Here's my question: I have the tools I need for graduating the plates, and I have a map on paper, but I'm not sure how to keep track of my graduation goals. I can draw the lines on the inside of the soundboard, but then I'm going to lose those lines as soon as I make a pass with the thumb plane or the scraper. Any suggestions for good methods to keep track of my targets while I'm removing the wood I've just written on?

Thanks for your help.

**Oliver A.** · Nov-02-2016, 4:16pm

This may help you if you study the photos carefully.
http://www.apitiusmandolins.com/A-Mo...ng%20page.html

**Marty Jacobson** · Nov-02-2016, 4:38pm

Whatever your process is for gauging as you work, you really need to measure with some kind of deep-access calipers frequently. There are too many ways to misjudge your thickness, and taking the extra time to measure frequently ends up saving precious time and wood.

**sunburst** · Nov-02-2016, 6:31pm

I use a marking caliper. It looks like a light duty violin caliper, it can be set to a predetermined thickness, it has a soft lead (like pencil lead) so that it can make a mark, like a contour line, all the way around the top/back where the top/back is the set thickness. Before I use it, I carve my minimum area to my desired thickness and I carve the center to my desired thickness, then use the marking caliper to make sure my graduations are symmetrical and done according to plan.
As for a graduation map, I don't use one. I just decide on what I think is an appropriate thickness for the plate in the center and the minimum area (according to the wood and the general sound I want) and then "connect the dots" using the marking gauge.