Rip-saws run from 4 to 7 points per inch; crosscut-saws from 6 to 12 points per inch.
In general, saws are of two kinds, rip-saws and crosscut-saws.
The _rip-saw_, Fig.

87, may be thought of as a series of chisels set in two parallel rows which overlap each other, for each tooth is filed to a sharp edge which, at each stroke, chisels off a small particle from the end of the wood fibers.
The shape of the teeth is the result of experience in uniting a number of factors: as, strength of the individual tooth, the acuteness of the cutting angle, and the ease of sharpening.

The steel of a saw is softer than that of a chisel, in order that it may be filed and set.
Hence it is weaker and the edge cannot be so acute.

A typical form of tooth is shown in Fig.

87, in which A is an edge view, B the side view, and C a cross section.