BAND SAW BLADES. Owing to the increased value of timber in America more and more attention has been paid to the eco nomical conversion thereof into the sawn prod uct ready for market. The methods in use a few years ago were found to be wasteful and usually crude, and the product turned out of but an indifferent quality so far as sawing was concerned.
The attention of the operator being directed to band saw blades, these have come into quite general use for various purposes. A test of the band saw blade has proven its advantages to be so great that it has displaced not only the small scroll or "jig" saws for bracket sawing and ornamental scroll and curved work, but has also displaced reciprocating saws and cir cular saws for heavier work.
A band saw consists of a thin band or rib bon of steel with teeth cut in one edge, the two ends being welded together, making it contin uous. When in use it is mounted on two wheels like a belt and made to travel at a rapid rate of speed by revolving one of the wheels. For scroll work its advantage over the recipro cating and jig saw lies mainly in the increased and uniform speed at which the saw blade travels which enables the operator to better control the work in hand and to feed the mate rial toward the saw constantly, and thus to turn out more and better work than would be possible with a reciprocating saw cutting on the downward stroke only. Its narrower kerf also is more economical of lumber, particularly in resawing.
In sawing logs the advantage of a band saw as compared with a reciprocating saw may be judged when we state that the band saw blade travels at the rate of from 8,000 to 10,000 feet per minute, whereas a reciprocating saw mak ing 200 strokes of 18 inches to the minute would only have a cutting speed of 300 feet per minute. The band saw traveling more than 20 times as fast as the reciprocating saw will nat urally perform nearly or quite as much work as 20 reciprocating saws. The single recipro cating saw, because of its limited capacity, was succeeded by what is termed in the United States a gang, in Europe, a log frame, and in Canada a gate. The gang saw mill for log sawing consists of a sufficient number of re ciprocating saws placed side by side in a frame to saw completely at the one operation an en tire log. The advantage of the band log mill over the gang lies in its adaptability to the saw ing of each log to the best advantage; as but one cut is made at a time, and as the face of the log is exposed to the view of the sawyer, he can judge through what portion of the log the next cut should be made to yield the best results. The circular saw turns out nearly or quite as much product as the band saw, but as it requires a much larger kerf, is far more wasteful and the finish given to the wood by the band saw is much superior. The success
of the band saw is due, first, to the skill of the saw maker in turning out saw blades of a tem per at once hard and tough, to retain a good cutting edge and at the same time flexible enough to pass over the wheels without crack ing; second, to the skill of the saw filer in "fitting" his saws. Band saws require to be "tensioned" from time to time when in use, due to the fact that the saw stretches on the cutting edge by the continuous strain on the teeth. By the word °tensioning° is meant the expanding of the central portion and back of the saw blade either by the use of a hammer and anvil or by what are termed "stretching rolls." The use of the band saw has brought forth an extensive line of saw fitting tools such as saw "swages" which are designed to expand the points of the teeth, "pressure side dressers" or "tooth formers" or "shapers" which are in tended to give form to the swaged points of the teeth, automatic saw sharpeners, etc. With the use of these improved appliances it was found that thinner and thinner band saw blades could be used, and for "resawing" purposes, that is, the sawing of planks and boards into two or more thinner pieces, this is especially desirable. The plank or boards to be resawn are fed to the saw by means of rollers. Saws as thin as .02 of an inch in thickness are suc cessfully used. Such saws remove a kerf of practically one thirty-second of an inch. In log mills the band saw blades are usually 12 inches in width and 49 feet long, of 14 gauge, and with teeth three-fourths of an inch long, and spaced 134 inches from point to pOint. The size of the gullet (between the teeth) must be abundantly large to hold all the sawdust gath ered during transit through the largest diame ter of log to be cut. Too small a gullet causes chattering of the saw. The strain put upon the saw is as much as the metal will bear and re main elastic, the object being to have the cut ting edge rigid, and yet the band as a whole able to adjust the shock of a sudden obstacle, like a hard knot. For sawing very hard wood the teeth are shorter and spaced one-third more to the foot and have very little set. For cut ting white pine and similar woods the gauges recommended for all widths of saw are as fol lows: Bands up to 14 feet long, 22 gauge; from 15 to 17 feet, 21 gauge; from 18 to 20 feet, 20 gauge; from 21 to 24 feet, 19 gauge; from 25 to 30 feet, 18 gauge. For hard woods like oak and beech, the thickness should be increased one number on each length quoted, and the teeth spaced closer. For cutting metal the thickness is increased three numbers in the gauge and the teeth spaced about 20 points to the inch, with little or no set. Consult Grim shaw, R., (Saw Filing and Management' (New York 1901) ; Johnson, C. L.. (The Saw Diction ary' (Seattle 1909).