Quickly gauge the ideal hole size for any dowel
Depending on the application, dowels sometimes need to fit tightly (for joinery) or loosely (for example, when used as axles). And, unfortunately, dowels don't always match their stated diameters. As a result, I used to find myself making a number of test holes to determine a dowel's best fit. Those days are over for me, and now for you, too!
Gather your drill bits, order them by size (I include numbered and lettered bits to give me as many choices as possible) and make a test board from Baltic-birch plywood. Lightly chamfer each hole so you can easily slide in a dowel and check its fit.
—Dan Martin, Galena, Ohio