"friction" and high pitched noise from zero clearance insert

I recently bought one of the Rockler phenolic resin zero clearance inserts. (http://www.rockler.com/product.cfm?page 714&filter=zero%20clearance)
I cut the slot by raising my sawblade through the insert as per the instructions (and in fact moved it all the wa up and down a couple of times to make sure it was cut cleanly)
However, now whenever I run the saw, there is a high pitched sound coming from the blade "rubbing" against the sides of the insert whenever the blade is at any height above the insert.
In addition to being annoying, I am concerned that this friction will suck power from my saw.
-- So, is such noise (and associated rubbing) normal? -- If not, what can I do about it?
(I was thinking about widening the slot on one side by adding a piece of paper as a spacer to one of the washers but am not sure how to do widen the other side. Also, not sure whether this would defeat the purpose of a "zero clearance" insert)
Note my saw is pretty well adjusted with runout of just .001" (actually, I imagine that the reason I am having this problem is that the runout is so little since with a larger runout or wobble, the slit would have been cut wider)
Thanks!
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The friction should be minimal and not enough to worry about. The noise is the same cavitation that sirens are based on. It small air- pockets (between the teeth) getting chopped up. Sometimes a squirt of TopKote quiets scuffing sounds down a bit. I am making the assumption that when you raised the blade for cut#1, it was adjusted to dead-nuts verticality. Bringing the blade up on even the slightest angle will give you grief.
As you use it, it will widen up all by itself.
r
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Althought the sound might be annoying, I seriously doubt that you'll notice any power loss. After all, a "Zero Clearance" insert should have "zero clearance".

I always make my own ZCIs so I've never used the specific ZCI you reference. What you report is the same thing I've noted when I put a new ZCI in service. My experience is that it diminishes and eventually disappears as the slot wears with use. How much cutting have you done with the ZCI in place.

Personally, I wouldn't worry about it.
Tom Veatch Wichita, KS USA
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Tom Veatch writes:

Haven't done much cutting yet -- but since my saw has bogged down before on ripping 8/4 hardwood, I was concerned about losing power - but it seems like that is not a real worry

Thanks!
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It will go away in time. Zero clearance means just that and a rub is common. Eventually it will wear and not rub. If you are concerned about it zapping power, you need a better saw anyway.
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blueman wrote:

I wouldn't worry about it. The noise may be caused by the air coming off the teeth of the blade "whistling" as they pass through the insert. In any event the slot will widen a bit due to slight deflections in the blade as it is used.
--
Jack Novak
Buffalo, NY - USA
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I haven't used that one but I've had a couple ZC inserts and did find that the howl was different for each - and often it was different with each blade I used. I also wouldn't be surprised if the phenolic was amplifying it by vibrating. You might want to try and dampen it somehow just to see if it made a difference but I don't know what I'd use or where I'd put it.
And as others have said, it will change as it wears.
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I suspect, as others have, that it's the cavitation of the teeth of the blade cutting the "stationary" air at the edge of the blade opening...it'll wear in so there is a little more clearance...that should take care of the high pitched howl...if you really need to quiet it done, you can speed the process by sanding the opening a little with a little sandpaper...JUST A LITTLE!!!
As to losing power to the close fit on the insert, if you're THAT close to the edge of your power, get a more powerful saw.
Mike
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