Saw Blade Kerf... What am I missing? Ugh!

I wouldn’t worry about what it says on the riving knife. Instead, a quick way to tell whether there could be a problem is to remove the riving knife, run a short cut (2” or so) into the end of a piece of wood, then see whether the riving knife will accept the wood with that cut width. If it binds or sticks, then you have a problem. My guess is that it will be okay. If the kerf is a little wide (the blade can wiggle in the cut), I would have no concern about that. The main point of a RK is to prevent the wood from contacting the back of the blade as it passes by. That’s what leads to a kickback. The other function of a RK is to prevent reaction wood from pinching the blade as it leaves the blade, also a potential kick back scenario.

When I first put a RK on my older Unisaw, I was using a TK blade—also a Freud Diablo. I took the wood down to the steel yard with a kerf sawn in it, and found that it fit 14 gauge perfectly. No slop, no binding. No worry about .0002” of anything. One of the first cuts I did was with some oak with a lot of built in wonkiness, and it pinched the RK so firmly that I couldn’t advance it any further. Made me glad it was there.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

Because 91/1000 doesn’t simplify but the closest fraction is 3/32”. The difference between the two is approximately half the thickness of a sheet of copy paper; insignificant to woodworking.

-- Rick M, http://thewoodknack.blogspot.com/

Ray, welcome to LumberJocks!

Sorry to hear that you are (have been?) ill. And here’s hoping that if you aren’t already on the mend, that you soon will be. A serious illness is what brought me to woodworking – the cancer has been left behind but it is full steam ahead with the woodworking.

The key thing is that the blade has a kerf that is larger than the riving knife. If the manufacturer specs the kerf in a decimal number, that is more accurate than a fraction so go by the decimal number. If you have a caliper that indicates thousandths, use that to get an accurate measurement of your riving knife. Any blade which has an equal or larger kerf than that number will work.

As runswithscissors says, you can do an easy check without a caliper by removing the riving knife, making a test cutand then checking to see if the riving knife will fit in the kerf.

-- Mark Kornell, Kornell Wood Design

If the riving knife is a couple thou narrower than the kerf, I don’t think that will be a problem.
You should still be able to push the wood through easily.

-- Everything is a prototype thats why its one of a kind!!

As mentioned previously, the important thing is that the total kerf be at least as wide as the riving knife. Keep in mind that the actual overall kerf width of the blade is the width of the teeth, plus the combined runout of the arbor and blade while in motion, which will always be a tad wider than the actual tooth width. IMO it’s better to error on the safe side, so I’d aim more towards the 3/32” TK blades with a stated width of a bit more than 0.094” if possible. The narrower Freud blades “might” be fine, but there are enough other comparable choices that there’s really no reason to chance it.

Tips for Picking Saw Blades

Bargain Blades

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

Do the RKs that are included with table saws come in any thicknesses other than full kerf and thin kerf? I can’t imagine the manufacturers would make an RK that would not work for any and all blades available within either of those two size designations. In other words, I think this is a non-issue, and there is no need whatsoever to “err on the safe side.”

Admittedly, I do sometimes see posts on here where people are grinding or sanding their RKs thinner to make them work, but I think something else may be going on there—namely that they are trying to use a TK blade with a FK riving knife.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

My saw came with a thick kerf riving knife. I had the same question about it, and got about the same answers that have been posted here. What I did was make sure the riving knife was dead center, or as close as I could get it to the blade. I haven’t had any problems with a thin kerf blade at all. Also the saw came with a thin kerf blade. Hope I got the thick and thin of this correct. Kind of confusing.
Gerald

Thanks all! I guess I was over thinking it and needed the guidance from those with more experience. I have narrowed it down to the TK WW II or the LU87R010 and a good crosscut which I’m still looking for. From what I’ve read, I tend to think a two blade process will be the way to go. Thanks again for the wonderful guidance.

-- Ray - Minooka, Illinois