Tongue and Groove Joinery

With the boards matched and aligned, it's time to begin creating the grooves. Always create the grooves first, as it's much easier to take a little extra off of the tongues to ensure a good dry-fit than it is to take more out of the grooves.

When creating the grooves, you'll want to remove the center one-third of material from the edge of the board. For the remainder of this article, we'll assume you're working with one-by material (1x6 or 1x4 stock, for instance). This means that you'll cut 1/4" out of the middle of each board for the grooves.

Set up your table saw with a stacked dado blade set for a 1/4" width. On most stacked dado blade sets, this will likely be only the two outer blades (with no chippers or spacers). Adjust the depth of cut to 1/2" and set your fence so that it is 1/4" away from the right outside edge of the blade.

You will want to cut one edge of each inside joint of your layout with a groove. It doesn't matter whether you cut the left or right side with the groove - just be consistent. I always cut the grooves on the right side of the joint and the tongues on the left, but that's a matter of personal choice.

Place the board with the face flat against the fence and the edge to receive the groove flat on the table. Holding the board securely against the fence and the table, run the edge of the board all the way through the blade. This will give a 1/2" deep, 1/4" wide groove all the way across the edge. However, to ensure that the groove is perfectly centered, turn the board around and run the same edge through the blade (leading with the opposite edge of the board this second time). This will ensure that your groove is perfectly centered on the edge of the board.