Woodworking is filled with "special tools" that are only good for one or two jobs. The only problem is they do such a good job for their special design that using alternatives can be tedious at best. Such is the case with dado blades. They are only good for taking out huge chunks wood, but in most cases trying to do this other ways takes so much time, most of us would not bother.
There are basically two kinds of dado blades. The Stacked Dado set is the most popular because in most cases is does the best job of cutting dados and rebates, but there is also something called a dado wobble wheel blade which can also be used for making dados and rebates. The problem with the wobble wheel is that the bottom of the cut is arced somewhat, and more arced as the dado cut gets wider. The problem with this arcing effect is it makes for a less than perfect fit.
Cutting dados using a stacked dado set is not difficult, at least seemingly. The idea with any dado cut is that the piece that is to be fit into the dado cut should fit snugly in order to make it structurally sound and for the glue to work as best it can. It is IMPERATIVE that you make test cuts with your dado set before making the final cuts. If you don't you risk making cuts that are too large, and then you will a whole bunch extra work trying to make up for the mistake. The first time you omit the test cut will be the last time you omit it.
The best way to figure out the width of the cut you need to make is to measure the thickness of the shelf or other structure that you will be inserting into the dado cut. BUT DO NOT take this as the last measurement, make the test cut, try our the fit and work from there. Using a tape measure, will, in most cases not be sufficient enough to get the fit you will need, You will need a more precise measuring instrument.
Selecting a dado set can be agony for many woodworkers. There are many to choose from of varying qualities and with different features ... here are some of the things to look for ...
First of all, for most woodworkers a dado set is not something you will use a lot. For a small number of woodworkers, you WILL be using dado sets a lot. This knowledge will be the first indicator of what kind of money you will want to spend on a dado set.
You will also find that most stacked dado sets come in 8 inch, or 6 inch. If you have a smaller table saw such as one with 1-1/2 hp motor or less, pick the 6 inch dado set. That is because there is less steel to spin which will help preserver your motor.
If you have 1-3/4 hp motor and more you are probably safe with the larger 8" stacked dado sets, of which there are a number to choose from. If you are only cutting dados once in a while and don't need to have super clean cut dados you will be very happy with a more budget minded dado set such as the Freud 8" Dado Set.
If you are a bit more discerning in the quality of your dados and need a wee bit better quality cuts you could move up to the Freud Super Dado Set. This set is similar to the basic set but has more teeth in the side cutting blades and more chipper teeth in each of the chipper blades. All of this makes for a bit smoother cut.
If you are cutting a LOT of dados, or you just like the convenience of fine cutting, the Freud Dial A Dado will be the set for you. It uses the same cutters and chippers as the Super Dado but instead of using shims, the Dial a Dado uses an expanding "click" system that allows for fine tuning the width of your dado set while it is still in the saw, by simply turning the click wheel to make the dado blade wider or narrower. Take note, this is NOT a wobble wheel, this is still a stacked dado and the adjustments are fine - they take the place of shims so you will not be adjusting the dado from say 1/2" to 3/4" with the click adjustment.
And finally the wobble wheel. I am not sure if you can still buy these little gems except at garage sales and flea markets, but they do have their place. If you are cutting mouldings on your table saw a wobble wheel is a perfect, and now you can make your best choice for what will work best for your shop.
Freud 8" Basic Dado Set
Freud Super Dado Stacked Dado Set
Freud Dial A Dado Set
Freud 6" Basic Dado Set
Fractional Digital Caliper
Copyright Colin Knecht