Trouble with a rip cut on a JetJPS-10s

Hello All

I am trying to rip some 36” x2” square Kari or Jarrah (not sure quite which) in half on my older Jet 10” TS.

The timber is hard; the timber square enough especially the adjacent faces running on the fence and the cast iron table top. Fence is square to the saw blade or within a 1/64”. And dead square to table. Splitter is in line with blade and fence square to mitre slots fwiw. Fence is a full length fence.

I am using a Freud thin kerf 24T ripping blade. The blade is probably a bit dull now and has two slightly chipped teeth. I have just cleaned the blade. The jet is only 1&3/4 hp, about 1300 watts.

There are two problems:

The saw is bogging down and burning, whatever I do with the feed rate and needs forcing, and it is binding on the blade and fence. That is to say if I get part way through the cut, stop and re-slide the wood back in place I can feel the binding sometimes on the blade and splitter which doesn’t make any sense. Sometimes not.

On one piece of wood the kerf opened up to 4mm so I put that down to tension in the wood. It could be the wood (recovered dunnage) is to blame.

I cannot tell if the binding is killing the feed rate or (and) the lack of cutting is to blame. But maybe I just am expecting way too much from a little TS. I bought it second hand 10 odd years ago. Maybe it has run out of erbs. I can get a new blade easy enough but I am not sure that is the proble.

Any thoughts appreciated.

regards

:?

You haven't got the blade on backwards have you? I did that once on my previous 2hp saw when cutting some 80mm River Red Gum with a 12" blade :B, couldn't work it out at first :?, but it made a hell of a difference when I did. :o When the kerf opened up was there discernable movement of the stock away from the fence at any point? Sounds like a new blade might make a very significant difference. :2tsup:

Not this time, but I have made that mistake on a circular saw!

I will go check the specimens, but I do not recall movement, maybe there was. The blade guard blocks part of the view sometimes.

Regards

don't suppose you can just do two passes?so lower the blade to half way through the material and run it through and then go again at full height.


wait I just re-read the post....

it's your thin kerf blade, I had this happen on my Sawstop, couldn't for the life of me work out why my work pieces where bogging down, struggling and basically jamming. the thin kerf blade wasn't taking off enough material to clear the riving knife properly and was jamming between the fence and knife.

go and put a full size kerf blade on and I bet all the problems go away, it 100% did for me.


you're actually meant to have your blade ever so larger (like 0.5mm) then your riving knife, this allows enough clearance for your work piece to slide past it, but small enough that it's not enough clamping force to overcome the blade if your split wood starts closing in on its self. I don't actually know what table saws are meant to take thin but I don't actually think its many of them

you thin kerf blade is probably around 2.3mm I bet if you measure your riving knife with a decent pair of Vernier's or micrometre it comes in around the 2.5mm - 3mm mark as most full kerf blades are 3.2mm to allow for a bit of clearance

Tend to agree with the above. A blade has to match the riving knife/splitter. Used to be the 3.2mm blade was standard but these days there are quite a few thinner blades around. Its about time suppliers did more about explaining that you just can't bung on any old blade.
Regards
John

Quote:

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Originally Posted by havabeer69

don't suppose you can just do two passes?so lower the blade to half way through the material and run it through and then go again at full height.


wait I just re-read the post....

it's your thin kerf blade, I had this happen on my Sawstop, couldn't for the life of me work out why my work pieces where bogging down, struggling and basically jamming. the thin kerf blade wasn't taking off enough material to clear the riving knife properly and was jamming between the fence and knife.

go and put a full size kerf blade on and I bet all the problems go away, it 100% did for me.


you're actually meant to have your blade ever so larger (like 0.5mm) then your riving knife, this allows enough clearance for your work piece to slide past it, but small enough that it's not enough clamping force to overcome the blade if your split wood starts closing in on its self. I don't actually know what table saws are meant to take thin but I don't actually think its many of them

you thin kerf blade is probably around 2.3mm I bet if you measure your riving knife with a decent pair of Vernier's or micrometre it comes in around the 2.5mm - 3mm mark as most full kerf blades are 3.2mm to allow for a bit of clearance

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You might be on to something. I just spent an hour and a half with engineer’s square, vernier gauge and straight edges tweaking the alignment of the principal components. The kerf is dead on the width of the splitter, maybe 5 thou under including paint, and any slight unevenness would tend to force the wood out slightly to the fence. Only noticeable on thick stock. I could get a modern Euro style half fence, but that would be quite costly. I will get , probably have to order, a full kerf 20-24 T rip blade and give it a whirl.

I will let you know how it goes.

regards

My saw came with 2 riving knives, one for full kerf blades and a 1.75mm thick one for thin kerf. The plate on full kerf blades is around 2.25mm, the kerf of thin kerf blades is 2.4mm (3/32") so, assuming the full kerf riving knife is the same thickness as the saw plate, it should be possible to adjust the positioning of the riving knife to clear the kerf in the stock to prevent binding. I'll give you it's a close run thing though.

Or you could just make another riving knife out of some thinner sheet metal.

Quote:

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Originally Posted by Wol

You might be on to something. I just spent an hour and a half with engineer’s square, vernier gauge and straight edges tweaking the alignment of the principal components. The kerf is dead on the width of the splitter, maybe 5 thou under including paint, and any slight unevenness would tend to force the wood out slightly to the fence. Only noticeable on thick stock. I could get a modern Euro style half fence, but that would be quite costly. I will get , probably have to order, a full kerf 20-24 T rip blade and give it a whirl.

I will let you know how it goes.

regards

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Simplest solution would be to take the riving knife out and make a thin test cut on some scrap or your actual piece. If it goes through fine (or further/easier then before) you know it was the riving knife.

Can always put wedges into the cut as you go if you're worried about binding

Quote:

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Originally Posted by aldav

My saw came with 2 riving knives, one for full kerf blades and a 1.75mm thick one for thin kerf. The plate on full kerf blades is around 2.25mm, the kerf of thin kerf blades is 2.4mm (3/32") so, assuming the full kerf riving knife is the same thickness as the saw plate, it should be possible to adjust the positioning of the riving knife to clear the kerf in the stock to prevent binding. I'll give you it's a close run thing though.

Or you could just make another riving knife out of some thinner sheet metal.

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On almost all table saws the blade is always hard against the spindle / arbor flange with the riving knife's inside (fence side) face aligned to the saw plate inside face. The plate (large washer), washer and spindle nut snug the blade up to the flange on the arbor / spindle. The riving knife is typically adjusted for standard kerf blades.

When installing a thin kerf blade and using the standard riving knife it is the outside face (opposite to the fence) of both the saw plate and riving knife that are now out of alignment. It is possible to adjust the riving knife on some table saws, or place a shim between the saw plate and arbour / spindle flange. But why do that? All you will be doing is creating a problem for when you go back to a standard kerf blade as the riving knife will then be offset to the saw blade plate.

As Aldav states, the optimal solution is to have a second riving knife or splitter for your thin kerf blades.

I rip a lot of thin boards to approx 600 mm long on my Woodfast TS250 using thin kerf blades. I don't use the supplied riving knife, in fact I don't use any riving knife because I use a "ripping sled" on the sliding table. It is not a "perfect solution" as there is still some risk of a thin rip catching the trailing edge of the blade, however the "fan effect" of the blade keeps the kerf open with minimal risk of it closing up.

When I rip larger boards I always (:rolleyes:) use the standard kerf blades with the supplied riving knife.

I've had a "roundtuit" list item to have another riving knife made from aluminium plate which is available in various grades and thicknesses including 1.0, 1.2, 1.6, 2.0, & 2.5 mm.

Hmmm.

I was unwilling to try without guard or splitter, but I did mock up a half fence from an old spirit level clamped to the main fence. This was somewhat high friction metal surface but it was available. I also banged in some wedges as the cut passed the splitter. I did note that again the ends of the wood were close to 4mm open at the end (on a test without wedges). It was *just* possible to complete the remaining two and a half cuts with some burning and struggling.

I conclude that the splitter is just wide enough to very slightly force the wood ends further apart than would be natural, with all its associated addition resistance and friction. Also that the blade is blunt as hell. Finally the wood is thick, and not quite perfectly square over the length of the piece (36”).

So I will get a new full kerf blade, and make up a proper half fence for ripping thicker timbers.

Possibly next later this year a good 3hp TS; but first get to the root of any technique issues.

I will let you know how the new blade and setup goes for posterity. :U

Regards all.

Quote:

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Originally Posted by Mobyturns

On almost all table saws the blade is always hard against the spindle / arbor flange with the riving knife's inside (fence side) face aligned to the saw plate inside face. The plate (large washer), washer and spindle nut snug the blade up to the flange on the arbor / spindle. The riving knife is typically adjusted for standard kerf blades.

When installing a thin kerf blade and using the standard riving knife it is the outside face (opposite to the fence) of both the saw plate and riving knife that are now out of alignment. It is possible to adjust the riving knife on some table saws, or place a shim between the saw plate and arbour / spindle flange. But why do that? All you will be doing is creating a problem for when you go back to a standard kerf blade as the riving knife will then be offset to the saw blade plate.

As Aldav states, the optimal solution is to have a second riving knife or splitter for your thin kerf blades.

I rip a lot of thin boards to approx 600 mm long on my Woodfast TS250 using thin kerf blades. I don't use the supplied riving knife, in fact I don't use any riving knife because I use a "ripping sled" on the sliding table. It is not a "perfect solution" as there is still some risk of a thin rip catching the trailing edge of the blade, however the "fan effect" of the blade keeps the kerf open with minimal risk of it closing up.

When I rip larger boards I always (:rolleyes:) use the standard kerf blades with the supplied riving knife.

I've had a "roundtuit" list item to have another riving knife made from aluminium plate which is available in various grades and thicknesses including 1.0, 1.2, 1.6, 2.0, & 2.5 mm.

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Thanks for that. My older Jet uses a splitter, of which I have 3 different heights, and to two of which the after market Shark Guard fits.

Adjusting the splitter is a right pain in the as it is retained by two clamp plates on two bolts each with its own back nut and lock nut, under the lip of the TS. The splitter has to come out for each micro adjustment to the back nuts. I really look forward to a TS with a riving knife instead.

I have a roundtoit lust as well.

Regards.

Have to agree with you, Wol, splitters are a complete PITA. My previous saw had a splitter, didn't take long to get rid of it and make some zero clearance inserts with a fixed 12mm high sliver of wood fitted behind the blade. Although not as good as a rise and fall riving knife it was much more convenient than the splitter. Because it was more convenient it got used where the splitter would not have been.

I've done the same for my JET TS. One for each of the blades I use; my combo blade requires a different splitter to my dedicated ripping blade. Splitters are made of timber, so can easily be sanded to the correct thickness in each case. I slightly taper the front edge of the splitter too. A good starting point is to measure sawblade tooth width (actual kerf), measure thickness of the sawblade plate, and aim for splitter thickness to be midway between the two. It goes without saying that the splitter has to be exactly in-line with the blade too, but I cut the notch to house the splitter at the same time as I bring the blade up through the zero clearance insert when I make them.

It is one of the good things about sawstop (pretty most newer saws have it now as well I think) is the rising riving knife. But it also just gets clamped in place and is indexed.

so you just spin a handle 90 degree and lift it out, and just slot it back in and clamp back in place.