Why do rip blades rip faster?

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Why do rip blades rip faster? They have fewer teeth than combination or general purpose blades, so the resulting gullets are larger. But I don't see most people feeding their stock that fast. So it doesn't seem like waste removal via the large gullets can be that big a plus.
I would normally think that more teeth would = more cutting would faster cutting.
Anyone have any good links to articles about blades and tooth angles and such?
Oh, and if a rip blade rips faster, will it also cross-cut faster? Ignoring quality of cut, of course.
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snipped-for-privacy@gmail.com wrote in

A couple things come to mind... when you rip a board, you're going with the grain. The board will come apart easier along the grain than it will across it.
Another thing to consider is that more teeth = more friction = more drag which means slower cutting speed.
If you want good links, you'll have to do a Google search yourself. They're out there, I found a page in less than 5 minutes demonstrating how hand saw teeth should be sharpened, with pictures even.
Puckdropper
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wrote:

Possibly the case, but my understanding is that more teeth = smaller bites. Take bigger bites with the teeth, and you can feed faster, but you sacrifice a little polish on the finished cut- my guess it that doesn't matter as much with a rip saw because it separating fibers as well as shearing them, so you can get a better finish with fewer teeth.
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Dancing with the answer. It's the angle of the tooth relative to the wood. You've probably noticed that raising the blade too high when ripping makes the job worse. That's because you're hacking rather than peeling. Angle of your plane an analogy.
With carbide blades, only the edges of the teeth are excess drag, but I'd say that was a negligible factor.
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Puckdropper wrote:

Two many teeth will also burn at too slow of a feed rate.
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well it depends on the wood and the blade. but the harder the wood I find more teeth can be faster. in tropicals I can rip faster with a forrest 30t blade then any rip blade no matter how few the teeth. same on the bandsaw. some wood rip with fewer teeth better some don't
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On Mon, 29 Jan 2007 19:57:12 -0800, Steve knight

??? What Forrest 30 tooth blade is _not_ a rip blade?

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J. Clarke wrote:

They sell a 30 tooth Woodworker II.
Chris
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On Tue, 30 Jan 2007 09:19:16 -0600, Chris Friesen

Which has what bearing on the question?
Calling something a "Woodworker II" doesn't make it a rip blade or not a rip blade, the number of teeth and the grind and set make that determination. Some Woodworker IIs are intended to be rip blades, some are not.
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J. Clarke wrote:

I suppose it's a question of semantics. I'd consider the WWII a combo blade, not a rip blade, regardless of number of teeth.
Unless you get into the custom grinds, the WWII blades all have 15 degree ATB. This allows it to do crosscuts, but it will almost certainly cut into its efficiency as a rip blade.
In my view a rip blade is dedicated to ripping as efficiently as possible. Generally this means a small number of flat top teeth. Like this, for instance:
http://www.amanatool.com/circular-saw-blades/heavy-duty-ripping-710200.html
Chris
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Early WWII's were and still are General purpose blades. In recent years you can get WWII's that are "Customized" at the factory to specifically Rip, Cut square bottoms for box joints or spines, and or to have different bevel grinds to suite your particular needs.
http://www.forrestblades.com/woodworker_2.htm#custom
See the bottom chart to order specific needs WWII blades.
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and I am saying my combo ww II rips faster and smoother then any rip blade down to 18t and it takes less power to do it too.
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Steve knight wrote:

Givent that I haven't done the comparison, I can't argue with personal experience. I wonder what Forrest could do if they set out to make a pure rip blade.
Chris
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They do make a Pure rip blade. Item # WW10206125 Description, WoodWorker 2, 10" 20 tooth, For fast rip of thick hardwood with out burning.
Look here and look at the top item of the bottom chart. http://www.forrestblades.com/woodworker_2.htm#custom
For the advanced table saw operator. Ideal for joinery and special uses.IZED WOODWORKER 2 SAW BLADES For the advanced table saw operator. Ideal for joinery and special uses.
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My experience: I have a Forrest WW2, also a Dewalt 24 tooth rip blade, an Oldham 40 tooth "Wizard" general purpose blade, and a few others. The WW2 gives the best, smoothest cut in a rip, but it is notably slower, and takes more force than either the rip blade or the other 40 tooth blade. This is on a 1 1/2 hp contractor saw. I suppose a 3hp cabinet saw might behave differently.
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On Sat, 3 Feb 2007 16:46:09 +0000 (UTC), snipped-for-privacy@sdf.lNoOnSePsAtMar.org (Larry) wrote:

I have some WWII 40T blades, but my favorite rip blade is a Freud 20T full kerf rip blade.
The Freud leaves a great edge, and I can go get a coffee and come back without burn marks!
P.S. NEVER leave a board on the saw and walk away!
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snipped-for-privacy@gmail.com writes:

Take out a piece of veneer, or a thin cutting of wood (1/16" or less, at a guess). Take a sharp utility knife, and make two cuts:
- one with the grain - one across the grain
Decide which one is easier to cut, and think about how you might change the design of the cutting tool to make it easier to cut the difficult one.
Alternatively, you could take a plane and try three directions:
- with the grain along the flat side of a board - side-to-side on the flat side of a board - any direction on the end of the board
Is there a difference? If so, then it is likely that different tools (or different flavours of the same tool) will do best on different cuts.
Then think about what saw blades do. Are they cutting like a plane, a utility knife, or something different? Look at a rip blade and a cross-cut blade, and perhaps a combination blade, and see the differences in the cutting method (shape of teeth, angles, etc.) You might also want to look at a good saw blade catalogue and get an idea of the many different tooth designs and what use the recommend for each blade.
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On 29 Jan, 05:37, snipped-for-privacy@gmail.com wrote:

Because they're ripping and not cutting. Find a copy of Hoadley and read the chapters on timber structure (lots of drinking straws in a stack) and cutting tool chip formation. When you rip, you're splitting the fibres apart along their weakest plane. You don't even have to cut the fibres themselves (much), just the weaker join between them. When you cross-cut, you have to cut each fibre crossways twice.
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wrote:

Nice theory, but it doesn't explain why a blade that crosscuts just fine may requires the wood to be forced into it to rip.
Try ripping with a triple-chip grind sometime, then try crosscutting, and you'll see a marked difference.
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J. Clarke wrote:

It's not just theory, it's fact. A crosscut blade has many teeth and therefore small gullets. It has comparatively more teeth in the wood at any given time, causing more friction. Second, the gullets are too small to effectively get rid of all the sawdust from ripping.
Chris
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