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Thread: How to assemble a dado blade?

  1. #1
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    How to assemble a dado blade?

    I've been given a Sears 932176 dado blade set. I think the set is complete, it has 2 circular blades, 4 thick chippers, 1 thin chipper and a few thin paper washers. I'd like to know how these pieces are put together.

    To cut the widest possible groove, I could put all the chippers between the circular blades and mount this stack on the saw. But the teeth of the chippers are wider than the rest of the chipper. So I don't understand what would prevent the side of the tooth of one chipper from striking the back of the tooth of another chipper. Is the nut on the shaft supposed to press the stack together so hard that the chippers don't change their relative positions? Or are there supposed to be metal washers that are mounted between the chippers?
    Last edited by Chris Padilla; 09-17-2008 at 9:56 AM.

  2. #2
    Stephen, yes, the chippers are placed on the arbor so that they disect the angle of the blade teeth...and as yu add more chippers, you keep on doing the same. No teeth should be close to each other. On the blades, they should be marked "in" and "out" . I assume the paper disks are their "spacers".

    What I would suggest you do, is put two outer blades on the arbor and cut a slot with it...and mark the blade combination. It should be about 1/4". Then add a chipper and cut the same board and mark...and so on. Keep that handy and it will help you set up for dados and grooves.
    John Lucas
    woodshopdemos

  3. #3
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    dont forget that u also need to keep the chippers perpendicular to each other. if u do a search on google you can find several videos about how to set up a dado blade properly. much easier to understand than by words alone!

    Brett g.

  4. #4
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    I interpret the "yes" to mean that when the chippers are set in some angle relative to each other and that the pressure of the shaft nut on the stack will be enough to keep them in this position. So if I tighten the shaft nut correctly, i don't have to worry about them shifting and hitting each other? The reason that I ask about this is that the paper washers wouldn't space the chippers far enough apart to keep their teeth from hitting if the chippers happened to shift positions and start to assume the same angle relative to the circular blades.

  5. #5
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    The blades and chippers should not rotate relative to one another on the arbor after they are tightened down. The teeth overlap so you can put in shims to widen the cut slightly, and you will not open a gap that would form a ridge in the cut.

  6. #6
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    Yes, the arbor nut when properly tightened should and will keep the chippers and outside blades secure, and they will not crash into each other. If they do, shut off the saw and run, not necessarily in that order!

    The shims allow you to make very fine adjustments to a groove so it may match the thickness of a board which has already been milled, or plywood whose thickness may vary.

    The same concept applies to stacked router bits (cope and stick for instance) and shapers, though the arbor diameter obviously varies.

  7. #7
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    Also, remember to make sure the chippers are rotating the right direction. The first time I used a dado stack, I had them on backwards (they weren't helpfully marked, like the outer blades were ). I kept wondering why I was burning the bottom of my cuts, and why it was so hard to push the piece through.

  8. #8
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    Also, if your Sears set is as poor as mine, you'll find the chippers don't dig quite as deeply as the blades. The blades each leave a deeper groove on the side of the dado. Not pretty, and not fixable as far as I know. (I'd be glad to be wrong about that, however.)

  9. #9
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    It should be fixable. Just have them sharpened at a good sharpening service (Forrest sharpens other brand saws) making sure that they understand that you want a completely, or nearly so, flat dado.

  10. #10
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    Brian,

    A common feature even with top quality dado sets is that the outer blades make a scoring cut just a tad deeper at the outside of the dado to prevent chipout; sets can be ordered without this feature, for a cleaner look if the dado shows in the finished work, or you can get the blades reground as Steve mentions. Any deeper than just a little, or a deeper groove (rather than just a scoring cut), well, that's just poorly designed set.
    Last edited by Frank Drew; 09-17-2008 at 10:00 AM.

  11. #11
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    Stephen, it sounds like you've never used a dado blade set before so I'll throw this tip in as well.

    The arbors on table saws are different lengths depending on the manufacturer. Some arbors are long enough to accept a full dado stack, all of the blades and chippers, and some will only accept a partial stack. Make sure that when you have tightened the arbor nut that you have at least one (1) full thread showing outside of the nut. This will help prevent the nut loosening and bad things happening like blades and chippers flying out all over the place.

    Congrats on you new dado blade set.


    hth
    Mark Rios

    Anything worth taking seriously is worth making fun of.

    "All roads lead to a terrestrial planet finder telescope"

    We arrive at this moment...by the unswerving punctuality...of chance.

  12. #12
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    Couple other things about that dado set (I have one rarely used over 20 years). Since the outer blades are hollow ground, a ¼" groove made with just the outer blades leaves a little ridge about 1/64" wide in the middle - annoying but not catastrophic since it is fairly easy to knock down with a chisel. Also, I never thought those cardboard shims (almost 1/16" thick) were particularly safe or reproducible. And then, it is steel and not carbide, so will dull pretty quickly on really hard wood or plywood.

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