Saw Blade Rake: Negative or Positive?

The rake on a saw blade's teeth affects the tendency of wood to move during cutting. Rake angle should be different for blades used on different types of saws. October 1, 2010

Question
Can anyone tell me the pros and cons of having positive and negative angles on circular saw blades? We have a cross cut that has a positive angle on its blade. It is very noisy and it bites. I was told by a rep that we are supposed to use a negative angle saw blade on a cross cut because a positive angle makes the blade bite the timber, which makes the machine unsafe to use. He went on to tell me that negative angles are quieter than positive angled saw blades because there is far less air compression with negative angles. Is this correct? I hope it is, because I've just ordered one of his blades for 110. It is 18 inch in diameter and has 54 teeth.

Forum Responses
(Solid Wood Machining Forum)
From contributor G:
Positive feed more aggressive and great if you have a power feed on your radial arm saw. If you do not, then the zero to negative (I forget if it is -5 or -15) eliminates (or at least greatly reduces) the tendency for the blade to self feed and pull itself to you, and sometimes up and over the board. That makes it safer and much easier to control without the death grip arm bracing needed to control an aggressive blade. It seems to make a modest difference chopping 2x4s for construction or small mouldings, but gets important quick with harder woods and longer cuts.

I presume with the horsepower and momentum of an 18 inch blade, an aggressive (positive) blade would be very dangerous. I also presume that your new blade will have the EU bite depth limiters.



From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Radial arm saws (or generally any saw where you move the saw blade into the wood) should always have 0 or slightly negative rake angles. It appears your rep was very knowledgeable in this area. However, a table saw (or generally any saw where the wood moves into the saw) with 0 or negative will likely kick the piece back at you... fast enough that you see it coming but too fast for you to get out of the way.


From contributor B:
All the above info is correct. If you are pulling the saw head towards you and into the wood, such as on a radial arm or slide compound miter saw, you want a negative rake. It makes the saw less likely to climb up the cut and into your hand or arm.

For a fixed blade machine where you are moving the wood into the blade, such as a table saw, you want the more aggressive positive rake angle, which I would agree is also safer in this situation.

I've never heard a report one way or the other for miter saws (non-sliding) although most of the blades I've used and seen on those are positive rake.



From contributor D:
We use both positive and negative rake blades in our shop. As noted above, for safety on radial arm saws, and on some dedicated aluminum cutting chop saws where a positive rake produces unwanted spiraled chips. I'd be nervous putting that thing in a tablesaw. I would personally have it exchanged before you use it.


From contributor d:
I reread and think you are putting this on a crosscutting saw? If so, negative rake is good. A ripsaw, unless it's a gang rip designed for negative rake, should be positive rake.