No branch of mechanics has received greater develop ment in the U n itled States than t h at which relates to woodworking. America has been pre-eminently a wood-producing country, and has brought sh a ping, planing an d m wing machinery into the greatest perfection. Soon after i t s introduction t he a pp arently weak band sa w was developed so as to cut the hard -est w ood of any thickness with accuracy, economy and convenience undreamt of. We illustrte in our present issue a machine which has apt I y been said to be an invention as revolutionary as that of the band saw. It is known as the chain saw mortiser. In indoor woodwork especially, an immense quantity of mortise and tenon work has to be done, and machines for the purpose have been used for many years. The mortising machines have been coinstructed on the general principles of the old hand chisel and auger, representing in their operation the processes of the human operative. These machines the chain mortiser rep laces, throwi ng into disuse the old chiseling processes, and substituting therefor a cutting tool which eats its way into the heart of the hardest or softest wood with the utmost rapidity, making therein a m orti se of mathematical accu racy of s h ape, cleali ng it of even the smallest chip and leaving no core to be knocked out. This work it does silently; the old chisel mortiser in full operation was a most disagree-able machine in the shop, while the chain mortiser wo rks almost in .silence. The chips which it makes are by its own action brought opposite to the suction orifice of a rotary blower, by which they are blown away, making it one of the cleanest machines which c an be u sed in the shop. The soul cf t h e machine is in its chain, which, with its sprocket and feeder bar, we i 1l u strate in one of our cuts. The chain is an !ndless one, somewhat similar to a bicycle chain, but with links toothed on the outside. The links may be divided into three kinds, arranged in s ucc essi on as shown in the small cut; some with two outside teeth and a clearance space bet ween, others with two intermediate spaces with clearance spaces outside and between, others with a single central tooth. The chain is rotated from a sprocket wheel at its upper end, as shown in the cut, while it is brought to a proper state of tension by the feeder bar which is seen at its lower portion. A wheel rotating on accurate roller joint s is carried by the lower end of t h e feeder bar. The right hand figure shows this roller with the j ournal cover plate removed. It is obvious that, if the chain is rotated in the proper direction, the edges of the teeth will cut their way through a piece of wood. In the machine the chain is mounted on the front. Beneath it is a working table on which the work is placed and clamped. By t he action of the mach i ne the face of the work is brought up against the chain so as to effect the mortising. The chain rotates with high velocity, and a deep mortise is made in the hardest wood, complete and ready for gluing in one or two seconds. The machine is carried on a large substantial base, on which a compact frame is supported, which carries the necessary band wheels and feed mechanism. When in action, the chain is kept constantly in rapid motion, its s peed varying from 1,800 to 2,300 feet a m inute, and its feeder bar projecting down over the work table. The work table on its front is adapted to be placed at different angles, so that the mortises can be made in any desired direction. From the front of the base projects a foot lever, by which the belts are shifted back and forth, a very ingenious arragement of parallel motion levers being employed at the inner end of the foot lever. At the right side of the frame rises a spindle, with two adjustable collars. As the machine is automatic in its motion, the upper collar is applied to regulate the depth of the mortise and its position determines the rise of the table. The work being put in position and clamped, a (Continued on page 356. )
This article was originally published with the title "The Chain Saw Mortiser"