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Wobble Wheel Dado Sizing Jig

wobble blade jigMany many years ago I purchased a Wobble Wheel Dado Blade. For those of you who do not know this blade, it is an interesting invention where a single blade is mounted in housing that when you turn the housing base, it offsets the wheel in stead of running true. The more you offset the blade the wider the dado it will cut. The blade works fine, although mine seems to be a bit sticky and harder to move in recent years. I have also heard many people who don't like wobble wheel dado blades, explaining that the blades don't give perfectly flat bottom dados because of their design, the bottoms are slightly convex or hollowed.

If you check out the previous video I did on this, you can see that ... yes, there is ... barely a dip in the dado cuts, but honestly, I think in most situations this would be more than acceptable for most people. I also have a stacked dado blade set that I use most often, mostly because it is more accurate for cutting size of dados I need.

Personally, my only real complaint with wobble wheel dado blades is that in order to get a snug fitting dado, you need to fiddle around with them setting, testing, re-setting and re-testing. All this takes time and I have always thought it would be nice to have some sort of a jig that I could use that I could set the blade width before putting it into the table saw, that would be accurate and give me the kinds of dados I want. 

I decided to try an idea I had to make a jig that could do this. I had plenty of scrap plywood around so set out to make a sizing jig, something I have never seen before, so it was brand new territory.

I first made a holder for the wobble wheel blade that would allow the blade to spin freely off the deck of the jig. I discovered that finding a 5/8" bolt to use as the arbor was a bit more of a challenge than I expected, but eventually I cam up with one. The only way for me to attach the bolt to the jig upright was to cut the head off and use the threaded part with a couple of nuts and washers and secure it to the upright.

Next I need to make the sizing pinchers. I surmised that the pinchers needed to be rounded on both the front and the back. This way it would not matter what setting they were at, they would be consistent in either thin or thick settings. The other point was that the the pivot hole needed to be absolutely in the middle of the pinchers otherwise the settings would be off.

After a couple of tried and failied attempts, I finally made a set of pichers that met perfectly in both the front and the back. I had decided earlier that if the pinchers were going to be out, I would use some rounded head screws for the jaws in both the front and the back, that way I could adjust the screws so that they met perfectly in the front and the back. Turns out I didn't need to use the screws as my wood cutting was accurate enough without them.

Mounting the pinchers was the next challenge. I knew that they should be on the same plane as the jigs arbour, so I cut a stand-off piece of wood that would be used to elevate the pinchers to that height. The first one of these I made, I used my hand drill to make a pilot hole for the threaded screw/bolt that would go into the the top, and screwed it in. Of course it went in crooked at which point I knew the pilot hole also needed to be accurate so on the second attempt I used the drill press to make sure the pilot hole was perfectly vertical. I then mounted the screw end into the stand off, lowered the pinchers on the bolt side and used a wingnut to slightly tighten down the pinchers.

With all this done it was time to test to see how this would work. All it really does is allow me to set the size of the width of the dados BEFORE I mount the wobble wheel in the arbor of the table saw.

My first attempt, for some reason the setting was way off. The dado I cut was much too wide for the wood. I'm still not sure what happened there, so decided to try it again. In my second attempt, if you listen to the me in the video, I say ... the setting might be "a bit skinny", meaning the dado groove might be slightly tight, and it was. After I made the cut and tried to insert the wood, it went in, but with a little bit of effort. But better that than being too wide. At least in a tighter fit the glue has some sort of a chance of working.

Int the end, the jig does work, just not as quickly and easily as I would like. Part of the problem with my wobble wheel, probably due to age, the adjustment collar does not rotate smoothly and sometimes sticks, which make setting even more challenging. One day I will update this blade and try IT in the wobble wheel jig. I'm looking forward to quicker and more accurate results with a finer working wobble wheel collar.

Copyright Colin Knecht

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