Questions & Answers Dado Blades
Reader Question: *Can you tell me the difference between a stack and a “wobble” dado blade? -Gabe Alexander Council Bluffs, Iowa *
Woodsmith Answer:
Basically there are two types of dado blades: adjustable (or “wobble”) and stack dado blades. While both are designed to make a cut that’s wider than a standard saw kerf, they do it in different ways.
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|The wobble blade (top) is easy to use, but the stack blade (lower) produces a better cut.|
WOBBLE BLADE.
A wobble dado uses a single blade that’s tilted on the arbor to cut a dado or groove between 1⁄4" and 13⁄16" wide (top photo in diagram).
To set the width, the blade has a beveled disk attached to each side. Adjusting these disks determines the tilt angle of the blade. The more the blade is tilted, the wider the cut. And because the blade is tilted, it appears to wobble as it rotates.
In theory, this sounds pretty easy to do. But when trying to fine-tune the width of the cut, I’ve found it’s easy to lose track of how much I’ve adjusted the disks. Another thing you’ll notice is wobble blades tend to vibrate. That’s because the blade is spinning off-center on the arbor. And that can leave more splintering and tearout — especially when cutting plywood.
And one final thing to consider is that because the blade is tilted, it produces a cut with a rounded bottom (upper drawing at left). This isn’t a big problem when making narrow cuts, but the wider the cut, the more exaggerated the curve becomes. If your project calls for exposed joints, a wobble blade will leave a gap that will be easily visible.
STACK DADO.
In contrast to a wobble blade, a stack dado uses multiple blades that are stacked on the saw arbor (bottom photo in diagram).
A stack dado consists of two kinds of blades — cutters and chippers. Cutters are the two outside blades that create the sides of the cut. Chippers are the inside blades that remove the waste left between the two cutters.
Most stack sets include four to five chippers and a set of shims that vary in thickness. Arranging them in different combinations will help you fine-tune the width of the cut. If you use all the blades and chippers, you can produce a cut that’s about 13⁄16" wide, just like a wobble blade.
Regardless of the number of chippers and shims or the width of the cut, a stack dado will always produce a smooth, flat-bottomed cut (bottom drawing at left). Its drawback, however, is the time spent finding the right combination of blades and shims to get a good fitting dado or groove. That’s why I built the gauge you see below. It tells me which chippers and shims to use to get a specific width of cut.
So, what’s the bottom line? A wobble blade is less expensive and easier to work with than a stack set. And for occasional use, it works fine. But if you’re looking for the best quality cut, I’d go with a stack dado blade set.
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|Each cut in this shop-made gauge is labeled to make it easier to find the right combination of chippers and shims for the best fit.|
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