Cut perfect grooves & rabbets without a dado set
Every once in a while, a project plan calls for a quick groove or rabbet; but installing and fine-tuning the width of a dado set really kills your momentum in the shop. This simple method for cutting grooves and rabbets guarantees a perfect fit, even in odd-size plywood, using the blade already in your saw.
First, cut a spacer
From a scrap of the stock you want to fit into the groove, carefully rip exactly a blade's thickness from one face. Make the cut about 1" deep, as shown.
Make your mark-precisely
Now mark the location of the groove using a scribing knife or sharp pencil. Set the blade depth to match the depth of your groove -- no more than one-third the thickness of the stock.
Establish one edge of the groove
Adjust your fence so the blade aligns with the near side of the marked groove, and lock it in place. Place the spacer against the outside of your fence, butt and clamp a stop block against that, and make the first cut.
Cut the second edge
Remove the spacer, and butt the fence against the stop block. Make your second cut (right). Now, make repeated cuts to clear the waste between them. (See opening photo, previous page.) Move your saw fence over the thickness of your blade's kerf after each cut.
Touch up the bottom
After clearing the groove, remove any ridges at the bottom with a chisel of the same width as the groove or with a strip of adhesive sandpaper applied to the edge of scrap shelf stock.
Rabbet = one-sided groove
Use this same technique to cut rabbets without a dado set. The addition of a sacrificial wooden fence prevents the blade from cutting into your tablesaw's metal fence.
Combo vs. Rip Blade
Rather than using a combination blade for cutting grooves, switch to a rip blade. The alternating top-bevel teeth of a combination blade leave ridges that weaken a glue joint if not flattened. The flat-ground teeth on a rip blade leave a smoother cut. When cutting dadoes across grain, however, a rip blade will cause chip-out -- use a combination blade in this instance for the best results.
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