I just installed a store bought zero clearance insert in my table saw and it is pretty noisy, compared to the non zero clearance insert it came with. The higher I raise the blade the noisier it gets, the side of the blade seems to be slightly contacting the insert. The blade is a thin kerf blade, I have also noticed this with a cross cut panel sled I made. Blade run out seems to be ok. Could the problem be the blades thickness, table saw or the operator?
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Replies
There is nothing wrong, you are just up against basic physics.
Anytime a moving surface with holes or slots in it brushes up against a fixed edge, small areas of very high air pressure are generated just as the edges of the holes, or saw teeth in this case, sweep past the fixed edge and "pinch" off a little bit of the air. These bubbles of high pressure air, as they expand, are what we hear as noise. The noise is worse when you raise the blade because the face of the teeth, where the pinching occurs, are closer to being parallel to the top face of the insert.
This phenomenon is exploited in creating sirens where they deliberately push air thru slots in a rotating cylinder mounted inside of another fixed slotted cylinder.
You may find that slightly filing away the side of the slot or slightly rounding the top edge of the slot will decrease the noise. Some of the noise, from the same effect, is also generated on the underside of the sled or insert at the back of the blade so adjustments there also will help.
John White
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