Here's a quick way to cut a dado on a table saw. It only requires a combination saw blade and two spacers. The spacers are used to establish the two sides of the dadothe material between the sides is
Spacer Thickness – The key making this work is the thickness of the spacers. The first spacer matches the thickness of the work piece that fits into the dado. (A scrap piece from the project works just fine.) And the second spacer equals the thickness of the blade. (I use a piece of 1/8" hardboard with a sing strip of masking tape.)
First Side – To cut the first side of the dado, start by clamping one spacer (the scrap from the project) to the rip fence, as you can see in the drawing at right. Then position the fence so the saw blade aligns with the near side of the dado (see detail 'a'). After locking the fence in place, butt the work piece against the spacer and use the mitre gauge to push it through the blade. Note: You can use this same technique for cutting grooves. The only thing to keep in mind is at the spacers need to be the same length as the fence.
Second Side – The second side of the dado is cut with the rip fence in the same exact position. Only this time, you'll need to replace the first spacer with one that matches the thickness of the blade, as shown in the photo above. With this spacer clamped in place, it's just a matter of making a second pass (see detail 'b').
Remove Waste – all that’s left to complete the dado, is to remove the rest of the waste. To do this, just "nibble" away the waste by making as many passes as needed (see detail 'b').
Ridges – One thing you'll notice about a combination blade is it leaves ridges on the bottom of the dado. If the end of the dado is going to be covered up, you can just leave the ridges. But if it'sexposed, you may want to sand the bottom of the dado flat. For a handy way to do this, take a look at the drawing at
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