saw blade height

[kityuser]

has anyone noticed the way that some tv programs of late are showing presenters who don`t lower the blade on thier table saw to "just above" the height of the timber that they are cutting (that sarcastic plonker on "cutting edge wood-worker is one).

does anyone else do this?

I notice that norm SOMETIMES does`nt lower his blade down when he is ripping sheets of ply, is there a specific reason for this?

for a physics point of view, you can treat the force exerted by a body travelling in a circle at its perimeter as acting at a right angle to the radius at the point where the force is acting.
So for a saw blade, raised at full height ripping some ply, at the point where the blade is cutting the ply, the teeth are exerting force nearly straight-down on the ply edge (into the floor effectively). But for a blade lowered so the the crown is just above the ply, the force is being exerted by the blade tip at a far more horizonal angle.

surely the "high blade" will cause far more chip-out/feathering ?????

the lowered blade will be more dangerous as the blade is trying to "spit the wood" back at the saw user???


what does everyone else do?

steve

 

[johnelliott]

I always lower it, I haven't run any experiments to check, but it just seems like the right thing to do

John

 

[Adam]

>surely the "high blade" will cause far more chip-out/feathering ?????

It's more efficient though, as it's acting closer to 90 degrees, however its more dangerous (with all that extra blade exposed) So yes, you get more breakout, but you can push the board through faster.

This has been the subject of lots of arguments both on-line, and by different views presented in books. I personally set the blade as low as possible.

Adam

 

[gidon]

It's a good question. I have tended to use the recommended tooth-above--the-wood-I'm-cutting rule. But did find I sometimes raised it because I was getting tearout. Thought it was something to do with my set-up. But interestingly this is discussed in this month's FWW. As A_L mentioned this a controversial subject but FWW suggest 1 inch height above the workpiece is recommended to reduce tearout. Their theory is that this transfers the force of the blade rotation in "such a manner that the fibers [American spelling] are pressed into the surface, resulting in a cleaner cut". Some safety caveats are also added.
But my personal suggestion is to follow the safe rule of a tooth above the workpiece, unless you have difficulties, then perhaps raise the blade and proceed with care!
Cheers
Gidon

 

[Philly]

yes, as Adam said, if you have the blade higher it alters the angle of attack as it cuts the wood. This can be handy if you are getting problems with tearout, etc. Try it, but be safe!
regards,
Philly