I am using Microvellum and an Onsrud CNC. I use blind dado construction for my cabs. We use melamine board, and it varies in thickness from .73 to .78. So of course this affects my dado being loose or too tight. Does anybody have a suggestion on the best way to deal with this? I have tried just going with the thicker stuff, but it makes some of the sheets' dados to loose. With using Mv, I can't adjust tool diameter on the fly to compensate for different thicknesses. Maybe I am being too picky on how tight I like my dado...
From contributor F:
If you index off the top of the spoilboard instead of the top of the part, the tenon will machine to the thickness that you have set in the program, no matter what the thickness of the material.
Usually if you stick with one manufacturer of melamine, you have no huge problem, as the variance is rarely more than a hundredth or so anyway. Another way is to machine the tenon face as well as the tenon itself to, say, .7 or so. You need to work from the spoilboard up for this. In other words, expose the core on one side of the tenon to a constant thickness and let the bottom of the dado take the inaccuracy. Say you use .75 as a nominal thickness. If the tenon is .25 long, make the dado .28 deep. .72 material will actually make the dado from the surface .25 again. Thicker material will make the dados deeper. If you stop dado both sides of the tennoned part, you also don't have to worry about the tenon bottoming out on one side only. Then again, there is always confirmat.