The bevel on the edges of a crosscut saw's teeth
The Varieties of Crosscut Teeth are legion: -- hook, crook, double hook, double crook, V's, M's, W's, and all their variations and combinations, with cleaners or plows in every possible alternation; and each or all of these in infinite difference of acuteness, set, rake, and cross-angle.
Fig. 170 shows an arrangement of teeth of crosscuts very popular in some quarters. The scorers or cutters are single teeth with alternate fleam to left and right. The cleaners or plows are of course shorter than the cutters; they are double, and have no fleam. We approve of the idea of giving no fleam to cleaner teeth, but highly object to the square-shaped gullets between the teeth, and also to the notches in the plows. These should have rounded outlines, which are easier to make and leave a stronger plate..
Source: Robert Grimshaw, Saws: the history, development, action, classification, and comparison of ... 1882, several pages, but page 112 has the most info, and several detailed illustrations.
Next to the hammer, the saw is the most important tool used by the woodworker. Saws are used for cutting lumber into smaller pieces, and when the cutting is across the grain, the teeth must be so sharpened that they will cut just as the point of a knife cuts when drawn across the grain. Such saws are called crosscut saws. Saws used for cutting parallel with the grain have the teeth filed like the edge of a narrow chisel, and are called ripsaws.Fig. 148. — Teeth Of A Ripsaw. Fig. 148 shows the teeth of a ripsaw. Fig. 149 shows the teeth of a crosscut saw.
The shape of the teeth also determines the use of the saw. Notice in the crosscut teeth that the sides make equal angles with the horizontal line while, one edge of the ripsaw teeth makes an angle of 90 degrees with this line, and the other side a variable angle. Saws for coarse work have large teeth, and consequently, in such saws there are fewer teeth to the inch than in saws intended for fine work. The size of the teeth is designated by so many points per inch. In a 6-point saw there are six teeth to the inch, and this number is stamped on the end of the blade next to the handle.
The bevel on the edges of a crosscut saw is called the fleam, and the wider this fleam, the sharper and weaker the teeth. The weak tooth will soon wear out on hardwood, and so a saw to be used on hardwood should have a narrow fleam. The angle at the front edge of the tooth affects the smoothness of the cut and the force necessary to push the saw through the wood. This can be illustrated by drawing the blade of a knife across the grain of a board, first with the blade held in a perpendicular position, and then held inclined at an angle less than 90 degrees. It has been found that the angle of 60 degrees in crosscut saws is the best for all-round work; and that in ripsaws, 90 degrees is best.
When a large board is to be sawed, it should be placed on sawhorses, and a large saw should be used. If the piece is small, it can be held in the vise or on a bench hook, and a small saw should be used. A back-saw is the name of a small saw with fine teeth and a thin blade, too thin to be used without a strip of metal on the back to prevent it buckling or bending. This saw is used in fine cabinet work.
Source: George Marshall Brace, Dexter Dwight Mayne, Farm shop work: practical manual training 1915 page 173.
Charles Barlow, of Chancery-lane. For improvements in saws. (A communication.) Patent dated July 31, 1851.
Claim.—The combination in the time saw of fleam teeth and chisel teeth, are described.
These improvements consist in manufacturing saws with fleam and chisel teeth combined, by which means the saws cut more easily, and are enabled to clear themselves more readily than those having one only of the above descriptions of teeth.
For saws which are intended to cut in one direction only, the fleam and chisel teeth are placed alternately, the former being set in opposite directions, as usual, while the latter have no "set", and act on the wood in the manner of planes, removing the stuff in shavings, instead of making sawdust; but when the saws are used for cutting in both directions, the teeth are arranged by twos (the cutting edges of each pair being turned in opposite directions), except at the ends, where there are a greater number of fleam teeth; both of these arrangements may, however, be varied.
Source: Iron: An illustrated weekly journal for iron and steel ..., 56 1852, page 118.
47. For an Improvement in Saws; Joseph H. Tuttle, Seneca, New York.
Claim.—"What I claim is, the combination, arrangement, and location upon the same blade, of the setts of fleam teeth for scoring the sides of the kerf, and the setts of planing teeth for removing the wood between the scores, when said planing teeth are placed back to back; curve in opposite directions, and are between the setts of fleam cutters, and at sufficient distances apart, so that each planing tooth shall serve alternately as a gauge to its fellow, while allowing it to cut to a proper depth, and be a permanent guide to the fleam cutters, to prevent any of the teeth from taking too rank a hold upon the wood, which makes it run with great ease and efficiency, and is applicable to slitting or cross cutting, substantially as described."
Source: Journal of the Franklin Institute Philadelphia, PA, 1853, page 84.
Sources: Iron: An illustrated weekly journal for iron and steel ..., 56 1852, page 118.Journal of the Franklin Institute Philadelphia, PA, 1853; George Marshall Brace, Dexter Dwight Mayne, Farm shop work: practical manual training 1915 page 173; Christopher Schwarz, "Premium Carcase Saws", Woodworking Magazine Issue 15, Autumn 2009, pages 26-29; note: Schwarz's article concentrates on the selection by woodworkers of several carcase saws currently on the market, but -- in passing -- also makes informative comments about the origins and uses of fleam.,