Disston lumberman handbook

The life of a band saw depends very largely on the way it is handled, particularly when it is new and before it has been perfectly adapted to the wheels on which it is run. Many men expect a new saw to do more work than one that has been perfectly adapted and adjusted to the wheels and the alignment of the mill. This is a mistake, for there are peculiarities about every mill, and until a new saw is adjusted to the face of the wheels, their aligning or tilt, the speed and feed, they cannot be expected to give as good results as the Saw which has been adjusted to the mill. There is a certain quality about a new band saw which we can best describe by calling surplus elasticity, and until this quality is brought down to its proper bearing by the judicious use of the hammer and saw stretcher in connection with the first "runs" of the saw, it will not be at its best. The manufacturer is not in a position to subject the saws he sends out to the same strains they receive in the mills, hence a saw will change more on the first run than on any succeeding one, and should be gone over with extra care the first time it comes off; in fact, if the system of running a saw only half an hour on its first run, then taking it off and touching it up wherever necessary, was more generally followed, there would be fewer cracked blades, and the life of all saws would be materially increased. All experienced filers and mill men know that excessive speed, too much tension, uneven tension, case-hardening, or glazing from the emery wheel, guin adhering to face of wheels, crystallization from too heavy hammering, cuts on the surface of saw from sharp-faced hammers, vibration of either machine or saw, sharp angles in the gullets, imperfectly adjusted guides, backs of saws too long or too short and excessively cross aligned to make them "track," insufficient throat room and hook, crowding the saw against guard wheel, will cause it to crack. These are all well-known causes of breakage, yet notwithstanding the knowledge that all band saws are more or less subject to these conditions, too often the cause of fracture is attributed to the quality of the steel or over-hardness. In justice to the saw manufacturer, due consideration should be given the fact, that the saw is only one item, while each and every one of the above named causes is a great factor in producing cracks in band saws.

We receive many letters from Band Mill owners and operators asking our advice as to the best manner to fit, tension and operate the saws to attain the best results in capacity and quality of the lumber made and at the same time get the most wear out of the saws. The best advice we can give our band-mill friends is to employ experienced and skillful handsaw fitters. Such men, compared with inexperienced band men, will save their wages many times over in the quality and quantity of the lumber manufactured, to say nothing of the saw bill, for inexperienced men invariably spoil a large proportion of the lumber manufactured and ruin one or more sets of saws before they realize the trouble lies in their lack of knowledge, hence we repeat, the services of competent band saw fitters are indispensable to the successful operation of band saws. It is impossible to lay down a set of rules to fit all cases, or answer correctly any single one without knowing all the conditions under which the saws are run, but we will give a few of the most important points in reference to the care and management of the band saw which, if followed out carefully, will benefit those who have heretofore neglected any of these points.

Vibration is one of the greatest causes of bad results in the use of band saws and, knowing this, particular attention should be given to the wheels and their shafts, the journals and boxes ; the wheels must be round and in perfect balance and the shafts must run free in their boxes with no lost motion.

Band Mill builders are giving less crown to the wheels than they were a few years back, some are making flat wheels. Each style has its advocates and will give good results when properly handled, and as some mill builders give one 64th of an inch crown in a 12 inch face wheel, it seems a question of education or preference with the operators.

Perfectly uniform tension is the important point, for if a saw has fast and loose spots in it, the tendency to crack is largely increased, the fast spot cracking from undue tensile strain and the loose spot from constant buckling of surplus metal.

After the saw has been properly tensioned it should be accurately fitted. The swaging and fitting of the teeth is practically the same as in a full swaged circular saw, the swaging being side dressed or shaped to a uniform width with an under and back cut in order to leave the extreme point of tooth a trifle the widest, the full amount of swage when side dressed should never exceed No. 9 gauge in a 14 gauge saw and in hard timber can be run with less clearance; it is advisable to run with as little swage as practicable for it decreases tensile strain on the saw as well as saving lumber in the kerf and requiring less power. It is also necessary to frequently resharpen band saws. Many saws are ruined by being run after they have become dull. No band saw should be run longer than two and a half hours on one sharpening.

Well tensioned and well fitted band saws, when properly handled, will stand the maximum feed and manufacture good lumber, but after the corners of the saws become worn or dull the saws will dodge or leave the line, which has the effect of destroying the tension and fracturing the saws.

The amount of "hook" ranges from four inches to six and one-half inches in a ten inch saw, being governed by the timber to be sawn and the amount of feed carried; when a properly hammered and fitted saw runs perfectly true on the wheels out of the cut, but "chases" back on the wheels as soon as it enters the log, increase the amount of hook until saw retains practically the same position on wheels both in and out of the cut.

In sharpening use a medium soft emery wheel and do not crowd it on its work as this would result in case-hardening the gullets. Cracks are liable to start from any of these case-hardened spots.

"Do not have sharp gullets to the teeth ; this concentrates the bend of the saw too much at one point as it runs over the wheels. Use a long round gullet, as large as practicable, with no sharp corners or abrupt angles.

Never let the back edge of saw come in contact with back guard wheel or any other hard surface, as case-hardening is bound to ensue from which cracks will surely result. Should the saw be accidentally forced against the guard and case-hardened, remove the glaze at once by holding a piece of soft emery wheel against back edge while saw is running slowly. Do not take for granted that the back edge of the saw has not been in contact with the guard wheel, try a file on the edge of the saw frequently as it has only to make one revolution with the back edge against the guard to do the case-hardening, and is done so quickly that it often happens without the knowledge of the operator.

It is essential to have toothed edge of saw tighter than any other part and to accomplish this without materially affecting the uniformity of tension, roll the saw a little longer on the back edge. Let the increased length begin at the point in saw where greatest tension shows and let the back edge show about % of an inch rounding in every five feet then tilt upper wheel forward enough to make saw have strong a pressure on wheel at back edge as at front; this will leave that part of saw between wheels with a tight toothed edge without subjecting it to that undue strain brought about by making tooth edge tightest by an all tilt movement.

The various articles in this book, describing the making of the goods, are essentially short, and while giving the general or most important processes many intermediate operations are not mentioned, which, of course also have an important bearing on the workman-ship and quality of the finished tool.

The interior views of the factory are from photographs of Sections only of Departments, and while serving to give some idea of the facilities, etc., do not by any means convey an adequate impression of the immensity of the Plant, which can only be appreciated by a trip through the Works.