Try raising and lowering the blade through the full range a couple times. If the plate is phenolic, it may never run as quiete as an mdf insert.

 

I think your right that it's the sides of the blades touching the insert. My guess is that if you do a little trim on the zero clearance with a file it will go away. One other thought is you have a bent blade or wobble in you arbor.

 

Check to make sure your blade is dead on at 90 degrees also make sure the insert is absolutely level with the top of your saw (not canted). You can also try running a piece of sandpaper that is wrapped around a thin piece of wood slightly smaller than the kerf of the sawblade through the insert. It helps widen the clearance just a smidge and quiets things down. If there is still noise, put a dial indicator on the blade and check to make sure there is no blade warp or arbor run out.

 

I doubt the insert is 'defective' - all it is is a piece of material with a cut line in it that you cut on your own saw.

a few thoughts:

1. +1 to Jims idea, if your cut wasn't clean, you may have some burr on the edges of the newly cut slot - use a file to lightly debur those corners and it may remove the excess noise.

2. if #1 didn't work, I would turn off the saw - unplu it from the electic outlet, raise the blade, and turn it by hand - slowly, see if you can fine any specific teeth on the saw that rub against the insert and cause a scratching noise, if these is ALL the teeth then your cut was off somehow (was the blade at exact 90 when you cut it? is it still at exact 90?), if it's just some of the teeth than you have a bent blade or your arbor is not running true (or the blade is not sitting properly on the arbor)- check for those

 

It will go away after a while.I have used thees inserts for a few years now on a couple of different saws and they always make noise at first.Make sure you dial in the fit by adjusting the screws on the sides of the insert!

 

^What Chipy said.

 

While the noise may go away with use as Chipy said, I'd still make sure the blade was flat and the arbor had zero play in it. It's good practice to make sure your tools are within spec and performing properly (or as expected).

And, as the others have said, a light pass with sandpaper might help a little more quickly. I'd try to figure out where the blade touches and then only lightly remove material from that area.

 

With the saw off, lower the blade all the way, then run piece of fine sand paper down each side of the kerf opening. If you can relieve the sharper corner on the kerf, it will help.

It will eventually go away with use, if you do nothing else.

 

I had the same thing happening to me on my home made insert. I cut a washer out of thin cardboard and set in on the saw arbor between the fixed flange and the blade. Then turned the saw on an raised the blade. Then I took the washer off. It worked for me.

 

It sounds unlikely in your case, but I'd consider the possibility of motor shaft bearings contributing to runout as well.

I mention this because, over several months, I noticed a gradually increasing rattle at startup and shutdown only with my ZCI and not with wider inserts. I readjusted the insert leveling screws and repeated the original setup cut of the ZCI. Got no improvement, so let it go. Wrong…

A few weeks ago, I found that drive belt tension was fine, but had a bearing squeak that I traced to the motor; the arbor bearings were noiseless and without any play I could feel. I replaced the motor only (under warranty) and my noise is now gone.

Looking back, my best guess is there was a certain amount of vibration transmitted to the blade despite belt drive and have added that to my list of things to consider if something sounds awry in the future.

 

I agree with the guys above you should check out your saws arbor.My comments assumed that your saw is in good running order if not the arbor my be bent if the noise from the insert dose not go away.

 

One other thing you can check is that you have the insert adjusted so that it really tight in the opening. If its got wiggle room, it will move and cause noise as it rubs the blade.

 

There's no such thing as a perfectly balanced, rotating, machine. You're dealing with manufacturing tolerances in both the arbor and the blade, and you're going to get some "flutter" as the blade rotates. Moving the blades location relative to the arbor and change the flutter, and even the tightness of the arbor nut can have an effect.

Your ZCI will eventually "wear in" and the noise will go away.

 

My phenolic one does this. I just endure it.

 

The instructions for the insert I got on my saw says that if you are getting excessive noise from the insert to run a file through the kerf a few times to knock off a bit. With the little amount your removing from the kerf, it's not going to cause issues with small pieces… Considering when was the last time you cut a piece that is only a few thousandths thick LOL…

 

It is unlikely that the simple introduction of a zero clearance insert will cause or reveal bearing, arbor or blade problems that did not exist before. If the blade cut through, then the slot is the exact size of the blade. What you are hearing COULD be simply aerodynamic turbulence. There's a lot of air moving off that blade with not much place to go because of the tight clearance. If it cuts ok and doesn't shake, do as Al does and ignore it.

Steve