Table Saw Dado Setup

While cutting a series of dados on the table saw recently, I realized that, by using a dial caliper, I was able to zero in on the correct width with only a couple of test cuts. In this post, I'll share the technique I used to set the width of my dado head to get perfect fitting dados.

  1. Measuring the stock with dial calipersMeasure your stock. Using the dial caliper, I measured the thickness of the stock at a bit more than 1/4 inch thick. Write down the exact number for later use. In my example, the thickness was 0.258 inches thick.
  2. Set up the dado head. Since the stock was about 1/4 inch, I used the two outside blades from my dado set. If your stock was thicker, you'd obviously use some of the inner chippers. Try to set up the dado stack so that it's a bit thinner than your stock.
  3. Make a test cut. Using the miter gauge, I ran a scrap piece of wood through the dado head cutter.
  4. Measuring the dado width with dial calipersMeasure the test cut. Unless you were exceptionally lucky, the dado is probably too narrow. Using the dial caliper I measured the dado width at 0.255. If your dado is too wide, you'll need to change the arrangement of your dado cutters, perhaps using a thinner chipper, if you have one.
  5. Insert shims. Subtracting the width of my dado from the thickness of my stock, I need to widen the dado head by 0.003 inches. The shims for my dado head stack have thicknesses of 0.002, 0.004, 0.008 and 0.010 inches. In this case, I chose the 0.002 shim. This should gets me close enough (this is only wood, after all)
  6. Make another test cut.
  7. Test the fit. Should be perfect. If the stock doesn't fit, a small amount of sanding is all that should be necessary to get the stock to fit into the dado.

What techniques do you use to get a dado to fit correctly?

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