I find that I’m asked pretty frequently about wobble (adjustable) dado heads. You can’t blame folks for asking. A wobble head is a lot less expensive than a stackable head. So why don’t woodworkers use them much?
About the Blade
A wobble head consists of one blade mounted on a hub. Dialing the hub allows the user to set the width of the resulting dado.
A hash mark on the hub points to a measurement, the resulting dado width. One of the things that’s cool about wobble heads is that they’re infinitely adjustable to any size dado. No shims required.
How Does it Work?
When the hub on the wobble head is set to its widest setting, 13/16” in this case, the blade is canted at a significant angle relative to the saw arbor.
When the hub is set to a narrow setting, 3/16”, the blade is nearly perpendicular to the saw arbor. The width of the cut is basically equal to the width of the teeth.
These shots were taken from above the saw. You can see the wobble action of the blade by watching its position relative to the dado insert:
As the blade spins it cuts one side of the dado…
then sweeps out the middle of the cut…
then cuts the other side of the dado.
…are a little icky. Although some wobble heads do better than others, this is fairly exemplary of the performance you can expect.
The dado on the left was cut by a wobble head, the dado on the right by a stackable head. The material is red oak veneered plywood. I just can’t get excited about the cut quality of the wobble head.
In addition to the surface having a lot of chips, the bottom of a dado cut with a wobble head is not perfectly flat. This affects glue strength, and is also a cosmetic problem when the dado shows.
The Bottom Line
As I pointed out you can infinitely adjust wobble heads from their minimum to maximum width settings. This adjustment can be made on the saw (with the saw unplugged and the arbor nut loose), and is pretty convenient. And with many wobble heads selling for less then $50, the economics are good. Cut quality in solid wood is better than in veneer materials.
Although wobble heads cost a lot less up front, if you’re serious about woodworking you need to invest in a stackable dado head. Overall performance is so much better. Additionally, over the life of the blade you’ll save money. Since the work is spread over a higher number of blades you’ll sharpen less frequently.