Originally Posted by
Peter Quinn
The blum formula boils down to subtract 5/8" from the opening for 1/2" drawer box material, to within a few thousands of an inch once you convert it to SAE. Frankly the difference in the plywood doesn't much matter on those slides but you could subtract 11/16" to make up for the 1/32" undersized plywood 2X if you really care to. My guess is if your sides are 1/8" off the slides either you miss measured the opening or the widths are not exactly right. But when you nail the numbers in both cases, use exactly 1/2" material, and use the 5/8" subtraction the drawers slip on like a glove...and not OJ simpsons gloves. If the drawer wont fit you must.....adjust it!
PS: I have run a very thin kerf up the bottom of the sides of a few drawer boxes in my past when the fit was just a bit too snug. You don't see this with drawer faces in place on applied fronts, drawers that are too narrow are a bigger problem on 563's than a bit too loose, so always err on the a little too big side if things are odd to measure, like 23 and "almost but not quite 3/8"....better to round up the width than down IME.