Do you agree?

[JimD]

I buy blades with as few teeth as will do a good job but that is because I am cheap. I do not think that blades with more teeth dull faster but I have never seen a good test. If an author states that he has done a controlled test, describes the test setup, and I see no errors, I will believe him or her. If they do not say they did a test or don't describe their test, I figure their opinion is no better than mine. I think more teeth = less work done by each tooth = gets dull more slowly, not quicker.

Heat and crud build-up, and crud causes heat, cause dulling (the heat causes little pieces of carbide to fall off). My rip blade with few teeth and agressive hook (Freud) does allow higher feed rate and doesn't seem to get hot (I have not noticed burning) but I don't think it will dull more slowly than the 50 tooth combination blades I use more often. My combination blades do not burn either when they are sharp and clean. Other than burning, I have no real way to judge temperature.

Jim

[TheRic]

There are several things that you have to remember when you try to figure studies / reports / etc out.

Theory and reality don't know each other exist.

For a study to be accurate it needs to be done in a tightly controlled environment where only 1 variable changes.

For a study to be practical it needs to be done in a real world environment where there are several variable that are changing.

My guess is that they tried to be to accurate, and ended up messing things up. They probably set everything up blade speed, type of wood, feed rate, etc. all the same. They only changed the # of teeth on the blade (actually they changed a few things like Dustmite mentioned). By setting the feed rate constant they were feeding the wood at the wrong rate in either one or both high & low tooth count.

As we all do, we tend to feed the wood at a different rate depending on the number or teeth, wood hardness, depth of cut, wood moisture, etc.
There is no exact science, it is what feels right. Sometimes we get that perfect cut, sometimes not.

It is hard to make a valid study / experiment when a major part is being done by someone who is making adjustments that feel right. Any results that are generated will be in question by everyone. Did the person feed it too quick, to slow??

[cabinetman]

I will say one thing though, considering the criteria needed to determine this is that a sharp blade cuts better than a dull one.

This statement in my post was an accurate a summation of this topic, that applies to saw blades. There are different blades for different procedures, and whether tooth count has anything to do with staying sharp longer or dulling faster is really moot. I pick a blade for the intended performance. As for creating an interesting and provoking discussion with little or provable facts, we have prevailed.



A THING OF BEAUTY IS A JOY FOREVER - John Keats

[cgallery]

As for creating an interesting and provoking discussion with little or provable facts, we have prevailed.

We bt3central users are just as interested in the theoretical as the practical.

[scorrpio]

How many times each tooth hits wood is totally independent of their number. If blade does 3000 RPM, each tooth will hit wood precisely 3000 times per minute. Assuming same feed rate, each tooth on a high count blade will take a smaller cut, with less chance to tear fibers, producing a cleaner cut. However, high count blades have less space between teeth, smaller gullets, so they don't clear the waste as well.

Applying a little geometry, one can calculate that a twice wider gullet has roughly 4x larger volume. Which means that even with its twice lower tooth count, it can sustain a twice the feed rate of a higher count blade and still clear waste adequately. And when not cleared, waste jams in the gullets and causes heat build-up and dulling.

So, bottom line: trying to feed a hgh count blade at a rate more suited to a low count blade, will cause the high count blade to dull quicker. Maintain proper feed rates, clean blades regularly, and either type will last a lot longer without resharpening.

[scorrpio]

If the feed is zero, then yes - but if not, EVERY tooth hits some wood. At 3000 RPM, on a 60-tooth blade and a feed rate of 6 inches per second, each tooth is presented with 0.002" of wood to cut. And each tooth hits its 0.002" of wood EXACTLY 3000 times per minute.

P.S. Was the post above mine just deleted?

[jseklund]

Just to update- I was reading a bandsaw book that I got for Christmas last night. Interestingly enough- they had a diagram. What it showed was that if you have a blade that has too few teeth, the cut is not as controlled and there is too much vibration. However, with too many teeth, the dust created cannot escape as it gets trapped between the small teeth and the uncut wood, which can lead to over-heating of the blade. I thought this may also be a factor that would be useful to know. As stated earlier in this thread, heat can be a factor in blade sharpness.

While this thread may appear theoretical- it COULD be tested. However, this is an instance where there is irony. It would be more impractical to test it than to gain insight from the theory. The theory may lead to practical applications (a test in itself).

In order to test this we would have to get two saw blades with the same shape teeth that differed only in the number of those teeth. We would also have to control or calculate the RPM of the blade- this would be more important than feed rate. There are just a lot of factors.

However, practical application of the theory will allow us to choose a better blade for the application, which is what everyone has agreed on. The right blade for an application is a must. But how to objectively choose that blade is the question.

I also had this thought. What if we took the extremes. Let's say we have a saw blade with ONE tooth. If this were put on a table saw, and used to rip wood, would it dull quickly?

Now let's take a saw blade with an infinite number of teeth. This would be a round blade, with really no "teeth"- just a sharp edge- like a round knife. I believe this would dull very quickly if you tried to use this for cutting.

Of course, we have a range in between- and other factors to consider, but it's interesting.

IMO- What we have learned is that too few teeth leads to an uncontrolled cut, fewer teeth is better for ripping/heavy work, more teeth better for finishing, and too many teeth will dull the blade and burn the wood.

[scorrpio]

I also had this thought. What if we took the extremes. Let's say we have a saw blade with ONE tooth. If this were put on a table saw, and used to rip wood, would it dull quickly?

Now let's take a saw blade with an infinite number of teeth. This would be a round blade, with really no "teeth"- just a sharp edge- like a round knife. I believe this would dull very quickly if you tried to use this for cutting.

IMO- What we have learned is that too few teeth leads to an uncontrolled cut, fewer teeth is better for ripping/heavy work, more teeth better for finishing, and too many teeth will dull the blade and burn the wood.

The first extreme already exists. Not exactly ONE tooth (that would unbalance the blade), but the chipper blades on my Freud dado have two teeth each. The carbide on them is gigantic compared to a regular sawtooth, and has so far held just admirably, producing many flat-bottomed perfect dadoes. However, the chippers only scrape the bottom, it is the side blades (which have more teeth) that work on the sides of dado.
A blade with no teeth exists as well. Every time you plane a board, you are ripping it with a toothless blade. Of course, the waste side of the rip is so thin, it easily flexes (or breaks) away from the thicker part of the blade. Trying to separate thicker wood in that fashion would require a lot more force and would be much harder to control.

[SARGE..g-47]

Good morning Ed...

I use a 24 Tooth blade for aggressive ripping and a 60 Tooth blade to get a smoother cross-cut even though feed rate has to be reduced as the gullet depth is less anept at removing the waste as the rip blade.

I don't know which dulls quicker. I just keep em clean and when they dull send them out for sharpening or replace them period. :>)

What I really wanted to address and possibly question is what you stated about an author knowing more than the reader because he is has been printed. Maybe.... and maybe not......

An article was printed in last months FWW mag titled: "Steel City 18' Band-saw Has Some Flaws" by a long time contributor which won't be named here. This article caused quite a stink at the FWW forum (Knots) as it was contested by Pete Bradley and SARGE in a thread on that forum titled "Steel City Smear".

The major "Flaws" the article stated they found were that the table had a crown of .024 with the Pin Out. The other major flaw he stated was that the blade twisted on re-saw because the upper guide bracket was mis-aligned. This article could be a major detraction to sales for the new Steel City Toolworks with excellent products trying to get a foot-hold if the author were on target.

He measured the table with the Pin Out! BS tables are ground with the pin in and it has to be there to ever achieve the degree of flatness that it was ground to at the factory. Mistake 1 by the author.

He took the BS off the pallet and started the test immediatley. Any BS has to be checked to make sure the wheels are balanced and co-planular, guides properly adjusted, table is square to blade, etc., etc.. ANY bandsaw and that includes the extremely expensive and commercial band-saws. Mistake 2 by the author as he admitted latter he was under a dead-line to cover his hinny.

He did not call Steel City when he thought he found the problem with the upper guides being "so mis-aligned" to warrant the title FLAWS. If a bracket had been indeed bent, they could have over-nighted one to him before assuming the test. Mistake 3 by the author.

If he had called SC or even observed the machine carefully, he would have discovered that the upper guide bar and bearings have adjusters that were added by SC purposely to allow their machine to be adjusted to a finer degree than any on the market including most very expensive competors. Mistake 4 by the author.

As multiple mistakes were made by the author and magazine for not having qualified machine proof-readers, it created a major stink because two of that forums readers and Steel City finally sub-mitting their own formal e-mail to FWW strongly contested the way the test was done and questioning the knowledge of the author about band-saws... Fine Woodworking has acknowledged the mistakes made an a formal apology to Steel City will be made in next months issue in the Letter section of the Magazine.

So.... even though the majority of authors do have an excellent working knowledge gained from experience of what they are talking about... it's not always the case and what they state should not be immediatley precieved as "Holy Grail" without at least some thought and close scrutiny. When your written text states you measured BS table flatness with the pin out you just gave the first "tell" that you are really clue-less on the subject.

You might fool the majority without a good knowledge of machinery and don't know what questions to ask, but you have just shown your Non-qualified status to those that get their hands dirty with machines every day for a living.

So... at least Question when you feel a question might be Appropriate!

Regards...

[Ed62]

Good evenin' Sarge. I'm late getting here today.

Good morning Ed...
So... at least Question when you feel a question might be Appropriate!

That's exactly why this thread exists. It's been very interesting to me, to see the thoughts of other people on this. Not only that, but I actually learned a little!

Ed