The cutters are very ingeniously arranged, and at many cases all four sides of the board are planed down, and the tongue and groove cut in the edges at one operation. The cutters may be so arranged as to produce curved surfaces by following a pattern or model which controls the depth of the cut, and are extensively used in the manufacture of moldings, panels, etc. These machines also cut rebates and grooves and do a limited amount of shaping. They can be run at several different speeds, whichever may be best adapted for the kind of wood being worked_ Moldings are, however, usually cut on special machines with upright spindles, the cutter-head only being above the table. Some have two spindles and two cutters, so that both sides of a strip may be modeled at once. They are run at a speed of 5,000 feet per minute.
Mortising machines are of two classes: (1) in which the cutter is chisel-shaped and works with a reciprocating motion; and (2) in which a revolving cutter is used. Large machines of this type, as used in shipbuilding, usually carry a rank of chisels on a single frame, so that mortises may he cutting at the same The blocks to be mortised are adjusted on the feed table so that each chisel cuts its proper chip, and scores for the next chip; each succeeding chisel cutting deeper into the wood. A machine for the ordinary shop, carrying a single chisel, is actuated by a link motion so that each successive blow is deeper than the previous one. Or the depth may be arbitrarily controlled by the foot of the operator on a treadle. Tilting tables enable the mortise to be cut on the bevel if desired. These machines operate at the speed of about 400 strokes per minute. To this class also belong the dove tailing machines in which the cutters are arranged in gangs, similar to a gang of chisels, or revolve upon a vertical spindle. They cut out the tongues and spaces automatically. Wood-working lathes are similar in principle handles, gun stocks and shoe lasts are produced. Other machines involving the lathe principle are the various kinds of borers for drilling holes; tenoning machines and mortising ma chines for making tenon joints and the mor tises to receive the tenons; and gaining ma chines for cutting grooves. Abrading machines are of two kinds— those in which an endless belt coated with sand or emery is brought in contact with the work, generally of small di mensions; and those in which a drum similarly coated is employed to work down large sur faces. Or they may take the form of simple disks of sandpaper or emery paper glued to a face plate.
to those employed in metal-working. The piece of wood is held between the stocks of the machine and revolved rapidly, while a chisel or other tool is pressed against it and removes a shaving by a combined paring and severing action. By the use of various automatic du
plicating attachments in conjunction with pat terns, as in the case of the Blanchard lathe, in which patterns and blanks are revolved together, exact facsimiles are readily obtained, and the output of the machines greatly increased. By these machines such irregular shapes as axe Practical very important place occupied by the circular and hand saws among the various classes of wood-working machines demands a few practical suggestions and rules relative to their use, care and man agement. The principal points to be observed in this connection are as follows: Hanging the Circular saws should always he hung upon the mandrel with the side marked •log side' next to the log on the mill, and should he perfectly plumb when the flanges have been screwed up. Thin saws and saws driven at high speed should be put up very open in order to allow the centre to pull through. These saws when hung on the man drel may be concave or convex on the log side when at rest, but when running at the speed for m hid' they are hammered they should straighten un and be flat on the log side. The difficulties resulting from too much crowning or dishing on the log side may be overcome by the use of suitable paper rings placed between the saw and the collars, so that when the saw is clamped between the flanges it will be brought to the proper position.
teeth are in the best of condition; but, when th• teeth have lost their sharp edge, the saw dodge whenever it runs against the slightest obstacle. Speeds too low are also objectionable, but they do not produce such ruinous etle.:ts upon the saw. These difficulties may be par tially remedied by the hammering of the saw, but it is impossible to overcome them complete!. by such means. The accompanying table gives the proper speed of circular saws of varyini; diameter. It is calculated on the basis of a periphery speed of 9,000 feet per minute. As general rule, however, saws for portable milk Lining the Saw with the Track.— The track should be solid, level and straight, and should be put down by careful measurement so as to be from one-eighth to one-quarter of an inch farther from the saw at its centre than at a distance of 20 feet from it. Some saws re quire more inclination toward the track than others in order to hold them to their work on the log, and if the track is properly adjusted any small variations from the required inclination may be effected by means of the set screws on the box.