Get step by step video instruction on how to set up and cut dadoes and rabbets. A rabbet is an L-shaped relief, cut at the end of the case side. A dado is a U-shaped cut that is typically used for a case bottom or fixed shelf. A groove is a slot that is cut parallel to the grain, but it is called a dado when it is cut perpendicular to the grain.
Adjustable dado heads, also known as wobble heads, are inexpensive. The dadoes they produce, though, are not flat bottomed, so they typically have weak joints. Additionally, adjustable heads tend to chip plywood veneer and leave an unacceptable face.
Stackable dado heads are like a blade sandwich, made up of two rim blades and a number of chippers. The cut quality from a stackable head is much better than that of the adjustable head.
Dado shims are used to change the width of a stackable dado head in tiny increments. They can range in size from .002-in. to .020-in., allowing you to tweak the width of the dado until it is perfect.
Take some of the trial and error out of your set up by using a Dado Gauge Block. It is constructed from a series of dadoes, each one cut incrementally larger than those before it. Slip your material into each dado until you find the perfect fit.
Stackable dado heads include two blades called rim blades, which must be used on the outside of the stack. They are left and right specific. Install the rim blades so their teeth point toward the outside of the cut.
Stack the dado head on the saw arbor, making certain that none of the teeth are touching each other or any other parts of the blade. Insert dado shims as required and tighten the arbor nut.
Set the height of the dado head by using a gauge block. This is typically easier and more accurate than measuring.
When making the cut, use a push pad to hold your material down on the table saw. When necessary, use a miter gauge to stabilize the piece so it doesn’t twist off the fence.
After making a test cut, check the fit of the dado. If it is too tight, add dado shims to the stack. If it is too loose, remove a shim. Check the depth of the dado and increase or decrease the blade height as required.
Make the depth of your dadoes and rabbets 1/3 the thickness of the material. Cut 1/4-in. deep dadoes and rabbets into 3/4-in. thick case sides.
The dado is a perfect fit when you can slip the part into it using only hand pressure. A mallet should not be required. There should be enough friction between the two pieces to hold them together as you gently pull on one of them.