A quick dado tutorial
A dado is a square cornered, U-shaped slot cut into wood. Technically, it is a slot cut across the grain. A slot cut with the grain would be properly termed a groove, but most people just call both forms by the name dado. When the dado is so close to the edge that instead of being U-shaped it is instead L-shaped, then we call it a rabbet or rebate cut.
A dado head for a stationary circular saw can take two forms. One is the wobble dado. The wobble dado has its blade set at an adjustable angle to the axis of the arbor on which it mounts. Then, when the arbor turns, the teeth sweep through a volume wider then their own width. The other form of dado is the stacked dado. In this version, one mounts a number of different blades, often of various thicknesses, creating in effect a single very wide blade.
The number of teeth largely determines the cost of a blade. Since a wobble dado has just a few teeth it is relatively inexpensive. A stacked dado has many more teeth and therefore tends to cost more. Finally, a wobble dado has a tendency to leave a slight curve to the bottom of the dado. Whereas the stacked dado tends to have a flat bottom with very slight grooves in the bottom on either side of the slot. These grooves are sometimes referred to as bat-ears.
Now, on to the Avenger 8 x 42 tooth Super Fine Stack Dado set. I had been in need of a dado set for some time, but the cost of a set always held me back. At the time, the Freud version could be had for $160 and the highly regarded Forrest version cost $250. I sat with $80 in my budget and pondered buying yet another straight-sided router bit and putting up with making multiple passes to get the job done. Then, meandering around the Amazon site I stumbled across the Avenger 8 x 42 tooth stacked dado set. It cost $80! I agonized over the decision for a few hours. A lousy dado set can be hard to adjust, make poor cuts and dull quickly. However, I had a whole pile of cabinets to make and using a router to cut the dados was not on my list of things to look forward to. Finally, I bought it.
When it arrived I was quite pleased with my initial inspection. The teeth were very well ground and nicely sharpened. A variety of shims were included and they miced out to the stated dimensions. The package that the set shipped in was designed to open and close easily so that it could serve as a storage box as well as a shipping container.
But, the proof is in the performance. Mounting the blades to my saw I made a cut with just the two outermost blades. This should give a 1/4-inch slot. My calipers revealed a result that measured 0.2505. Putting together a stack that should measure 3/4-inch, I made another cut. This one came out at 0.751.
Satisfied that the dimensions of the blades were good, I started in on my cabinet project. Two-hundred and forty linear feet of dados later, the blades were still cutting clean accurate slots in the oak-veneer plywood. This left me feeling very good about their durability.
It has now been a year since I started using the set. I have used it both on my table saw and in my radial arm saw with good results in both cases. The bat-ears on the bottom of the slot are present, but not very pronounced; maybe 1/64-inch in depth. Since I do not use exposed dados in my work they are of little consequence to me.
I am happy. I suspect that I could get a little bit better performance from the Freud or Forrest sets, but I seriously doubt that I could get enough to justify the 2 to 3x cost increase.
Is it a must buy? No. There is little that a dado set can do that cannot be done with a less expensive router bit. But the router bit risks blowout when exiting the side of the work. Also, cutting a deep slot may require multiple passes of a router, but only one with the dado blade.
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