Circling back to the Wobble Blade or Adjustable Dado blade as it is more accurately called, and because of its small diameter or 7 inches, it lends itself to making things that most other blades cannot do ... like coves and bowls, not to mention decent dados.
Watch it on Youtube: https://youtu.be/RRy8lxCoLag
My attempt at making these bowls, was actually for making concaves for nesting boxes for cavity-nesting birds, and a video that I first made about 12 or so years, then another update a few years after that where I used the fence on the table saw as the anchor ... which worked for that saw, but for my newer saw it was not quite as convenient so I devised a new jig to do the job along with some new techniques for trimming bowls ...
The inspiration for re-doing this topic is because of an email from Jack in West Virginia who tells me he has made 130 of these little bowls in the past couple of years and he calls them "catchall bowls" which I thought was a fitting title for them, thanks to Jack for the email.
Before You Begin
I recognize that this technique of bowl making on the table saw may look risky to some viewers and if you are in ANY WAY fearful of this technique or not entirely sure how it works I encourage you NOT to attempt it. All woodworking does pose risks and dangers to injury and anyone who is not familiar with the machinery and the techniques no matter what machine they are using should seek professional instruction. Do NOT operate any machine or engage in any woodworking endeavor that you feel uncomfortable doing.
Like many woodworking jigs the dimensions of the jig or usually not that critical so here is a list of the parts and the sizes of the ones I made, all in inches
Base - 3/4 x 6 x 9 (note: the 3/4" should be a full-thickness to accommodate the mag switches, so better quality plywood may be needed)
Magwitch holes - 1/2" from edge and 1" from back
The top main plate where the hinge attaches - 3/4 x 3 x10 (a hardwood is best for this)
Pivoting arm - 3/4 x 2 x 12
Pivoting Arm guides (need 2, one on each side) - 3/4 x 2 x 3 (hardwood also best for this)
Riser blocks to be able to raise and lower top block - 3/4 x 3 x 10
Pivot block that will be attached with screws to your bowl blank - 3/8 or 1/2 plywood, either 4x4 or 5x5 should work fine
Magswitch 150 (you will need 2 of these) if you have the Magswich 95s now, I suggest installing 3 of these
Hardware, one good quality hinge, 2 - 4" fully threaded bolts, with washers and wing nuts, another bolt to be cut off for the pivoting pin
How This Works
First of all MAKE SURE your jig is secured to the table saw. Then, with this jig you lower the Wobble Blade to just below the deck of your table saw so it cannot cut your bowl blank, then with one hand you hold down on the jig arm then slowly crank the blade up into the wood a small amount, then spin the wood you are carving, all the while holding the pivoting arm, then crank the blade up another small amount, spin the wood ... and so on until you achieve the desired bowl depth you want.
To remove the bowl, crank the blade down, turn the saw off, and when the blade has stopped spinning remove your bowl.
Point To Consider
The Wobble Blades have a large hub so they can only be cranked up about 5 full turns, check your saws ability
Watch the placement and length of screws you will be attaching your pivot block with, you do not want the wobble blade to hit those screws
The amount that you crank the blade into the wood can vary depending on the wood but small amounts each time are best and don't take that much longer to do, I prefer about a 1/4 turn each time and they are easy to keep track of.
Here is a link to an Adjustable Dado Blade on the Amazon Store to read more about it - HERE
As I have said many times in the past, you can often pick these blades up in good condition at swap meets and garage sales, just make SURE there are NO CHIPPED TEETH
Do I NEED to use a Wobble or Adjustable Dado Blade?
The advantage of the Wobble blades is their small dimension of usually around 7". If you have a smaller stacked dado blade such as 6 inches, this could be used with the 2 outside cutters only.
An 8" stacked dado blade using the 2 outside cutters could be used but is not recommended because of the increasing size which will likely limit the depth of cut as well. 7-1/3 Circular saw blades are not recommended as the teeth are too narrow.
What Woods Are Best?
Harder woods are best. Now, this does not mean "Hardwoods" because some hardwoods are actually quite soft, just as some softwoods are actually quite hard. Woods that are softer are easier to cut but often leave tearout. Ideally, medium-density woods works well.
Laminating different color wood together is another great source of wood and an endless array of designs. These are a great way to use up the scrap pieces of wood you have been saving for so long.
You can cut some "biscuits" off a log and use these, but be aware of a few points. The blade will often "burn" these kinds of wood because you are cutting into end grain. This just means more sanding may be required. Another point with log biscuits is their tendency to crack as they dry. If you use green wood, they will crack and probably quite quickly. These can still be attractive and can often be repaired after they are fully dried with CA glue.
How do I Sand and Finish these Bowls
There are a variety of small thee sided sanders that can work, I found that my small random orbital sander worked fine, along with some hand sanding. There are also "sanding mops" available that may work well such as the one shown below.
Sanding Mop available from Amazon Store HERE
In terms of a topical finish, whatever you currently use to finish the wood should work fine, with or without wood stains or dyes.
Whatever you do, work safely, take your time and ensure you are making all the steps in the correct order, and see what kinds of bowls you can turn out ...
Copyright Colin Knecht
If you are interested in reading more and even order these versatile Magswitches, please click on Colin's affiliate link below to save money purchasing these, and the best one for this job is the Magswitch 150