Tablesaw blade height rip setting and kickback

This is a follow-up to the "smooth-cutting rip blade burns cherry" thread.
Some comments were made suggesting that setting the blade height higher above the workpiece would allow the blade to cool more and burn the wood less.
Howard Acheson quoted a Freud rep as saying that "half a tooth above the workpiece" was the correct setting for all Freud blades, assuming you were using the right blade foer the job. This is obviously a very low setting.
Tage Frid, an old master whom many of you may know, or know of, said that he always set his blade at the maximum height because the blade would be cutting downward when it enters the wood and there's less potential for kickback.

If you look at the direction that the blade is trying to move the wood with a high setting versus a low setting, there's a very big difference. Tage's rationale makes sense to me.

The "blade cooling" comments would also support a high setting.
What do you think?

Jules, it is cutting downward as it first enters the wood, but you have to remember that it is also lifting up at the back of the blade and as you push the wood on through the cut, if the wood touches the blade for ANY reason at that point, it will try to lift the wood and if there is not a good hold down and splitter back there, it can cause a Very serious kickback. There have been several postings of this happening with pictures showing the board and how it lifted and tracked across the blade as it was thrown back with a violent force. You might search the files here to see those pictures.

There are several schools of thought here on this subject and I won't try to convince anyone which method to use. I normally set my blades from about 1/4" to the full tooth depth above the wood, (depending on the blade in use). My thoughts for doing this is that as the blade is raised higher, it has further to travel while gripping the wood, should there be a kickback, and that this would cause the force of the thrown wood to be much greater. Who knows, I could get a kickback tomorrow, but so far it has worked for me for over 55 years, (after a little demonstration by a fellow that convinced both my Dad and I that we had been doing it wrong for a few years), but one can never become lax when it comes to safety which includes a Well Tuned Saw with a good splitter and a good sharp blade suited for the cut.

Right, wrong, or indifferent, that's my story, and I'm-a stickin' to it. :D

I also set the blade just about "half the tooth" above the stock ... but by that I mean not just the carbide tip of the tooth, but half the entire gullet between the teeth.

For me, it just seems right to have less possible exposure to the hard, sharp metal of the blade spinning very fast near my hands. Were something to happen, I think 3/8 to 1/2 inch of spinning metal is probably less destructive than 3".

Safety and being scared to death of seeing so much blade spinnng at me precludes me from raising it much above the stock being cut! :)

Raising the blade to it's full hieght would scare the heck out me :eek: . I keep mine about 3/8" above the board, or just a bit higher than the depth of the gullet. I do change that from time to time for sheet goods to control splintering.


Brian :)

Jules. I read your post on the original problem, very curious. Cherry is problematic at best when cutting. It seems like that blade just isn't working out for you. You have done everything I can think of to mitigate the problem. Maybe the grind angle on the sides of the teeth are causing problems? Who knows.
I don't think that setting the blade to full height is going to effect enough cooling to stop the burning. Cherry is a fairly "mild" wood. If you are not having problems with maple, then blade cooling isn't the issue.
I typically set all of my blades to a height of the gullet, and 1/2 again the height of the gullet more, over the surface of the material. I don't have any scientific reason for this. This is the just the way I was taught in 1971 and it seems to work. I think that as long as the full gullet clears the material that is sufficient.

I cut a lot of cherry and have experienced the same problem. In experimenting, I've found that the higher the blade, the less burning I get. Just from wild guessing, I assumed that it was because there is less tooth contact at the higher setting, and therefore, better cooling. A wider kerf also seems to help by limiting contact with the surface of the blade. But still, I also noticed that green cherry will burn no matter what you do, and burls are impossible to prevent it. (maybe it's the sugar content).

Like others have said, I don't like the blade high either, but sometimes I just have to dive in I guess.:rolleyes:

Jules, I keep my blade low purely for safety reasons. I did a big project in cherry recently and cut what I am sure was several hundred running feet of 3/4 cherry. I did get some burning but honestly not much. I use Norm's advice about cutting blanks about 1/32" wide and then run them through the jointer - which removes any burn marks.

The Freud rep that I heard talk was more concerned with how many teeth were in the wood. If I recall it was something like three teeth. So it revolved around selecting the correct blade for the job, number of teeth on the blade and thickness of the stock.

You raise the blade to the point that you have three teeth on the cutting side buried in the wood as it revolves. That determines the correct blade hight.

My father always told me to raise the blade until the gullets just clear the surface of the piece you were cutting.

The "all the way up" makes the most sense but would limit, depending on stock thickness, how many teeth were cutting at any given time.

Being frightened of all that spinning blade sticking up might be a good thing, not a bad thing. I always pay attention to where my fingers are in relation to the blade and what would happen if something went wrong. The instant I don't feel comfortable, I shut the dang thing down and rethink what I am doing.

I too have seen Freud on a number of ocassions state the 1/2 carbide tip height for their blades. I personally believe that this is more a marketing thing than anything else. Today's blades are all being judged by how smooth the resutant cut is and as such, with a very accurately ground blade that has all the new anti-vibration stuff in it and adjusting the blade this way, all the cuts are burnished. Hence in any magazine tests you'll receive higher scores.

Personally I do about half the distance of the tip to the gullet and for critical cuts use the proper blade and not a combination.

The Forrest rep at the shows recommends a high blade. Other than the exposed blade being a bit less safe, it makes sense. The individual teeth rely on the chips to cool them. If the wood is scorching, there is too much friction and the heat is not being sufficiently removed. This heat causes the teeth to dull more quickly. Dull teeth create more friction/heat. More heat dulls teeth. ..dull lteeth .. .. .. .. well, you get the idea. A well-aligned saw will have an absolute minimum of drag as the teeth emerge from under the table on the upstroke. Usually, this can be determined by scoring of the sides of the cut in the opposite direction as the teeth which are cutting in a downward arc. That said, I run my blade very high, use a splitter and/or guard whenever possible, have and use a pair of Grrrippers, and feel very safe in doing so.

Bob said what I was going to mention...Forrest contradicts Freud on this, but in the context of their blades. I've followed the Forrest advice (I use their blades) and have had good results. Any burning is usually due to operator error...like not making the complete cut in one smooth motion. (Stopping)

The high blade is technically better.....just make sure the push stick is the closed type. If the piece you are ripping is narrow I lower the blade to just above the piece

Jules

Most recommendations are 1/2" above stock. I have a WWII blade that I am using to build a cherry curio cabinet and found I had to raise the blade 1 1/2 inches above my cherry stock when ripping to prevent burning. when crosscuting 1/2 seem to work fine.

The reason for the burn according to well versed members of this forum is when the blade is low you have more blade surface rubbing against the wood building up heat and that cause the burn. Whereas: Raise the blade equal less blade surface rub result with less heat less burn.

when you raise the blade take all precautions to prevent injury.