Make a Hardwood Cutting Board

Now that you've cut the grooves, its time to cut the corresponding tongues in boards 1 & 2.

Add some chippers to set the width of your stacked dado blade to 1/2", and lower the blade height on your table saw to 1/4". Move your fence to 4-1/2" away from the blade and run boards 1 & 2 through the blade on both sides to create the tongues that will fit in the corresponding grooves in boards 2 & 3.

TIP: For the best fit, set your dado blade to just less than 1/4" height and cut the tongue, then try to dry fit it into the groove. You might need to raise the blade a hair and run it through the saw again, but this will procedure ensure a tight fitting tongue-and-groove joint.