Messages Archive

Subject:
A discussion of 7 1/2" thin TS blades

Bill Tindall, E.Tn.
I think some of the concern expressed over free hand ripping discussed below stems from experience using a 10" blade and lack of experience using a thin 7 1/2" blade.

What anyone will notice when moving from a typical 10" blade to a 7 1/2" is the remarkable decrease in the force the blade imparts to whatever is being cut. This decrease results from a tooth up to 1/2 as wide and 1/2 as tall, and tip speed 3/4 that of a 10" blade. When ripping a full 1" ash board with the blade described earlier the friction resistance of the wood sliding on the table is the primary force one feels pushing wood through this blade.

The concern ripping is for a loss of control leading to the teeth catching and throwing the piece being cut. With almost no resistance from the blade cutting, what is being cut is easier to control. The smaller teeth are less able to get good purchase to initiate flinging the board out of control. The much heavier 10" blade has almost 10 times the energy to transfer to a piece going out of control and accelerate it back toward the person sawing.

A 7 1/2" blade has been the primary blade on my table saw for the past decade.
When I need to use a 10" bade I am anxious about the increase in care I need to use to keep the wood under control and the concern of the result if I loose control. I avoid using a 10" whenever possible.

In demonstrations I have initiated a rip cut on a small piece of lumber with a 7 1/2" blade and then just let go of the lumber and stood back. Either nothing happens or the lumber slowly moves back away from the blade. Don't try this experiment with a 10" blade.

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