"It might be easier to center the two different sizes by drilling the smaller hole through and center the larger on that hole. You can also prevent tear out by drilling toward the larger hole with the first drill."
"The size of the box has more to do with volume than tone if you're building straight acoustic. Full size dulcimer VSL ranges from about 25 to 28 inches with a few shorter but higher toned dulcimers. IMHO dulcimer building is much like cbg, if…"
"I would think their ages would make a difference in size but you might try a standard ukulele size. VSL is about 20" and you should find calculator at stew-mac or other sites online. You might look at mandolin charts too."
"Using a penetrating oil may darken the tone as it sinks into the pores of the wood--which is fine if that's what you want. Most pro instrument makers will finish with shellac, varnish or another film type finish, which sits on the top of the…"
"If you're playing with dulcimers you're in good shape in DAD. DAD and DAA are standard tunings. Try your .042 an octave lower for GDG and it it's too loose, rattles, or you don't like it, try a heavier string."
"I agree with Jim Burt, respect the tools and potential dangers, even more so with power tools. For the most part, hand tools can cut and cause lots of problems while power tools can maim and take body parts if not used carefully and correctly."