I have a Craftsman carbide-tipped 7" stacked dado set that I have had for several years. I had never noticed it before but recently discovered that when I cut a 1/4" dado, the dado is actually 1/4" + another 1/64-1/128" (a 1/4" drill bit is loose with side-to-side play, a 17/64" bit is a tight press-fit). I have cleaned the blades with no improvement. I examined the body of the plates where they mate together and find no nicks or dings.
Yeah, I know - I should buy a better set but am retired and money is very tight and I'd rather spend what I have on wood. I have given some thought to lightly honing the mating sections with sandpaper on a marble slab (this sounds like a tedious process: sand, assemble the blade on the saw, cut a dado, check the width, etc.) but it is about the only way I can think of to correct the problem.
Anyone out there have a better idea or any suggestions as to what grit sandpaper I should start with - 400 wet/dry?