Frustrating riving knife


bleedinblue

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After my initial problems getting the Grizzly 715 set up I have been very happy with it.  Aside from Sawstop's finger savers, I don't think I could ask any more from a saw.  However, once in a while, the riving knife seems a bit too tight and I have to abort mid cut.  I assume this just happens when a particular board has more tension than another.  I always end up fiddling with it, then get frustrated and take the knife off for the cut.  Only about half the time when I do that I can see the cut closing back up after passing through.  When it does that I use a long, thin piece of scrap to keep the back end of the cut under control.

Whats to blame more here?  The possibly out of adjustment riving knife?  The wonky lumber?  It's got me considering a full kerf blade to make sure the thin kerf blade and the riving knife aren't too close in thicknesses...I think they are verrrrrry close.  The blade is a new'ish Freud Fusion, but I tried my other blades (all thin kerf) and had the same results with each.

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When I bought my g0690 I only had thin kerf blades, and didn't pay attention to the riving knife specs (who reads the manuals).  I had all kinds of problems with my cuts jamming mid cut.  I polished the knife, waxed the knife and cussed a lot.  I switched to a full kerf blade and never looked back.  I don't know about your saw but the manual for my saw specifically stated no thin kerf blades while using the knife.  But like I said I ignored that part of the manual. 

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Think about it. Your thin kerf blade is making a kerf narrower than your knife. When the board gets to the knife, instead of it holding the pieces apart, it must now push them apart, to the left and to the right, into the fence, which ain't gonna move, creating a bind

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1 hour ago, Just Bob said:

When I bought my g0690 I only had thin kerf blades, and didn't pay attention to the riving knife specs (who reads the manuals).  I had all kinds of problems with my cuts jamming mid cut.  I polished the knife, waxed the knife and cussed a lot.  I switched to a full kerf blade and never looked back.  I don't know about your saw but the manual for my saw specifically stated no thin kerf blades while using the knife.  But like I said I ignored that part of the manual. 

Sounds familiar, lol.  

41 minutes ago, K Cooper said:

Think about it. Your thin kerf blade is making a kerf narrower than your knife. When the board gets to the knife, instead of it holding the pieces apart, it must now push them apart, to the left and to the right, into the fence, which ain't gonna move, creating a bind

Certainly, if the knife is thicker than the blade.  

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One factor could be that the Freud thin kerf blades are thinner than some other brands. When I looked into it for my saw (I've got the almost identical Ridgid) I found that the Freud only gave about 3 thou of difference between the kerf size and the riving knife size, which some people found was a problem. The one Freud Diablo blade I tried seemed to be on the verge of jamming. I put on a Dimar thin kerf blade instead, and it's about 10 thou larger kerf so there's no issue. It's worth looking at, anyway.

If I remember right, the knife is 90 thou, the Freud blade was about 93-95 thou, and the Dimar blade was 105 thou.

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4 hours ago, bleedinblue said:

After my initial problems getting the Grizzly 715 set up I have been very happy with it.  Aside from Sawstop's finger savers, I don't think I could ask any more from a saw.  However, once in a while, the riving knife seems a bit too tight and I have to abort mid cut.  I assume this just happens when a particular board has more tension than another.  I always end up fiddling with it, then get frustrated and take the knife off for the cut.  Only about half the time when I do that I can see the cut closing back up after passing through.  When it does that I use a long, thin piece of scrap to keep the back end of the cut under control.

Whats to blame more here?  The possibly out of adjustment riving knife?  The wonky lumber?  It's got me considering a full kerf blade to make sure the thin kerf blade and the riving knife aren't too close in thicknesses...I think they are verrrrrry close.  The blade is a new'ish Freud Fusion, but I tried my other blades (all thin kerf) and had the same results with each.

This is your problem right there..  I tried a thin kerf with my saw, a General 3HP, but had the same issue. Or see if you can get one made at a local metal shop for thin kerf.

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2 hours ago, Sac said:

This is your problem right there..  I tried a thin kerf with my saw, a General 3HP, but had the same issue. Or see if you can get one made at a local metal shop for thin kerf.

I'm not at all attached to thin kerf blades.  I went thin kerf because it's only a 2 HP saw, but I'm sure the saw can handle it. 

23 minutes ago, krtwood said:

Here's what the Grizzly manual says

Riving Knife/Spreader Thickness    0.1 in.

Required Blade Body Thickness     0.071 – 0.094 in.

Required Blade Kerf Thickness       0.102 – 0.126 in.

Craziness, because I know I put calipers on the stock blade and it was the same thickness as my thin kerf Diablo blades I had on hand.

 

As far as I'm concerned, this solves it and my next blade will be full kerf.

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27 minutes ago, krtwood said:

Here's what the Grizzly manual says

Riving Knife/Spreader Thickness    0.1 in.

Required Blade Body Thickness     0.071 – 0.094 in.

Required Blade Kerf Thickness       0.102 – 0.126 in.

 

That is going to knock out a lot if not most TK blades as they tend to run from .09 to .1".  A lot of TK blades made on metric standards are .091 and ones on imperial standards are 3/32" or ~.094".

4 minutes ago, bleedinblue said:

I'm not at all attached to thin kerf blades.  I went thin kerf because it's only a 2 HP saw, but I'm sure the saw can handle it. 

Craziness, because I know I put calipers on the stock blade and it was the same thickness as my thin kerf Diablo blades I had on hand.

 

As far as I'm concerned, this solves it and my next blade will be full kerf.

 

Sometimes the kerf of a blade is wider than a single tooth, it depends on the geometry.

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21 hours ago, SawDustB said:

 

One factor could be that the Freud thin kerf blades are thinner than some other brands. When I looked into it for my saw (I've got the almost identical Ridgid) I found that the Freud only gave about 3 thou of difference between the kerf size and the riving knife size, which some people found was a problem. The one Freud Diablo blade I tried seemed to be on the verge of jamming. I put on a Dimar thin kerf blade instead, and it's about 10 thou larger kerf so there's no issue. It's worth looking at, anyway.

 

If I remember right, the knife is 90 thou, the Freud blade was about 93-95 thou, and the Dimar blade was 105 thou.

I checked today and the Freud on the saw now has it printed on the side that the kerf is 93.  I checked it with calipers and couldn't find a tooth over 90.  Granted, as Huxley said, that doesn't mean the kerf doesn't get to 93 in practice.  Still too thin for my saw though.

I'm about to pull the trigger on a Carbide Processor, which I should do tonight since they say they have a 3-4 week wait.

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I checked today and the Freud on the saw now has it printed on the side that the kerf is 93.  I checked it with calipers and couldn't find a tooth over 90.  Granted, as Huxley said, that doesn't mean the kerf doesn't get to 93 in practice.  Still too thin for my saw though.

I'm about to pull the trigger on a Carbide Processor, which I should do tonight since they say they have a 3-4 week wait.

I would expect an individual tooth to be a little smaller, since they alternate. I hope it works out for you. I would have gone with full kerf, but with my saw being 1.5 HP I figured I'd stay thin kerf if I could. I did have to look around to find a half decent blade with the right thickness (great blades though, for the price, around $50, Dimar woodpecker). I'm pretty sure the manual for my saw recommended a blade at least 0.1 for the kerf. I know it came with a cheap full kerf on it.

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