I am having a problem with the assembly of my traditional face frame boxes. The problem is the dado and the irregular plywood thickness. I am using under size bits to match what the plywood is supposed measure, but to ease assembly was thinking of using standard bits with the metric plywood which could result in some sloppy joints. I guess what I am asking is for is opinions on this situation.
From contributor J:
Basically what I do is to make sure the frame dadoes fully assembled line up with the inside dimensions of the box so if the box width inside is 13-9/16" the inside edges of those dadoes must be the same. Yes they need a little persuasion sometimes, but mostly to do with the plywood flatness end to end.
Also, ask yourself is it important to me or my client that this relatively obscure joint be precise? Or is it causing a problem with the structural integrity? Is it time effective and are you building $20,000 or $100,000 kitchens? Personally a 20k kitchen isn’t worth that and neither is a 50k.
When doing full beaded inset doors it’s more important that the face frame be square and uniform to provide better fit and finish. In my shop the face of the cabinetry is 70% of the cost and I don’t scrimp on the quality of my boxes (3/4" sides, bottoms and rails or tops and 1/2" backs). Paintgrade face frames get nailed, glued, and filled and staingrade gets pocket screws from the outside. The face frames are pocket screwed also.
After you know your dado size then you can rabbit the edge or edges of the parts that will be housed in the dado's leaving a tounge of the proper length and thickness for the dado. This will work on materials of varied thickness if you machine the tongues so that they lie between the cutter and the indexing surface while being machined, whether that indexing surface is the shaper or router table bed, or the table saw fence.