4. Those employing knives having straight edges for surfacing purposes and cutting the work to thickness.
5. Those employing knives or cutters for producing irregular surfaces upon the edges of the work.
6. Those employed to produce irregular surfaces on the broad surface of work.
7. Those employed to finish surfaces after they have been acted upon by the ordinary steel cutting tools.
CIRCULAR SAWS.
The thicknesses of circular saws is designated in terms of the Birmingham wire gauge, whose numbers and thicknesses are shown in [Fig. 3078], where a Birmingham wire gauge is shown lying upon two circular saws, which show the various shapes of teeth employed upon saws used for different purposes.
Fig. 3078.
The teeth numbered 1 are for large saws, as 36 inches in diameter, to be used on hard wood. Numbers 2 and 5 are for soft wood and a quick feed. Numbers 3 and 4 are for slabbing or converting round logs into square timber. Number 6 is for quick feeds in large log sawing. Numbers 7, 8, 9 and 10 are for bench saws, or, in other words, saws fed by hand or self-feeding saws. Number 8 is known as the “London Tooth,” because of being used in London, England, on hard and expensive woods. Number 9 is the regular rip-saw tooth for soft woods. Number 10 is the Scotch gullet tooth. Number 11 is for either cross-cutting or rip sawing by circular saws used on soft woods. Number 12, is for large cross-cut saws; the flat place at the bottom of the tooth prevents the teeth from being unnecessarily deep and weak. Number 13 is for cross-cutting purposes generally. Number 14 is for rip sawing on saws of small diameter. It is also used for tortoise-shell, having in that case a bevel or fleam on the front face, and no set to the teeth.