The model and the wood for the copies are fixed, say exactly 8 or 10 inches asunder, upon a rectilinear slide free to move from north to south, and which slide moves upon a second rectilinear slide free to move from east to west, these two slides run upon anti-friction rollers, and together support what is called "the floating table," upon which the work is fixed. The two movements of the table are under the guidance of the two hands of the workman, while he controls a third slide with his foot. The third slide, which is vertical to the other two, carries in the center a tracer of globular form, and also at 8 or 10 inches on the right and left of the tracer, cutters of the same globular form, which latter are both set to make about 6000 or 7000 revolutions in the minute. The third slide, which together with tracer and two cutters forms one entire mass, when left to itself descends with a moderate pressure thai sends the two cutters into the two blocks of wood, until the central tracer rests in contact with the model, the cutting then coases, and the slide is raised from the work by the treadle.
In this manner by a multitude of vertical incisions at different parts, the whole of the material might be cut away until the copies were reduced to the exact form of the model But it is a more expeditions mode, together with the vertical motion of the drills and tracer, to more the work about horizontally by means of the two slides, as in every such rambling motion, the cutting will cease when the tracer cornea in contact with the model. The only conditions are, that the cutter and tracer be exactly alike in form and aire, and that the distance between them, and also the distance between the model and copies, whether 8 or 10 inches or other measure, be fixedly preserved throughout the one process.
The above case, in which the work lies always horizontally, is that most uaually required; but when the work has to be carved on all three sides, as for example in brackets or consoles projecting from a wall, although the arrangement of the central tracer and the cutters parallel therewith partaking of a vertical motion in common, remains unaltered, the model and copies are all three adjusted so as at one time all to lie on their backs, at other times all on their right or left sides with the progress of the work. Sometimes this change is effected simultaneously by mounting them on platforms, that are situated on fixed, parallel, and equidistant axes, and shifting all three at one movement, by a simple arrangement derived from the ordinary parallel rule with radius bars.
In the case of figures carved in the round, or on every side, the central model and two copies are built above one wide bar, upon three circulating pedestals or turn-plates with graduations and detente, by which the three objects may be alike twisted round to face any point of the compass; and as the wide bar upon which the three circulating pedestals are built, has a tilting motion by which the three pedestals may be all alike placed either horizontally, or inclined, to the right or left in any required degree, until nearly vertical, it is clear that these two directions of motion constitute universal joints, and enable any and every similar part, of all three objects, to be presented to the tracer and cutters respectively.
Messrs. Taylor, Williams, and Jordan, of London, employ these carving machines for all the woods, and occasionally for soft stones, marble, and alabaster, and these machines as well as Mr. Pratt's are also contributing largely to the embellishment of the New Houses of Parliament and other buildings now in course of being erected.
Note L. - To follow Notes J and K on page 46. (Mr. Tomes's Patent Dentifaetor, for making artificial Gums, Teeth, and Palates)
Another variety of carving machine, bearing some analogy to that last described, was invented at about the same time as Mr. Jordan's, we allude to Mr. Tomes's Dentifactor, a machine for carving the artificial teeth, gums, and palates used in dental surgery: patented March 3rd, 1845.
This machine, like the last, is intended to make an exact copy from a solid model, but which in Mr. Tomes's case is a true counterpart of the mouth of the individual, produced by moulding. Thus an impression of the mouth is taken as usual in softened bees'-wax, from this a plaster cast is obtained, and from the plaster a model or impression is made in a fusible though hard composition, principally gum lac combined with a softer gum, which produces an exact reverse or counterpart of the gums; one that when carefully made fits so exactly to the surface of the mouth as even to exclude the air from between the model and gums, and is therefore capable of being retained in position without springs, simply by atmospheric pressure. The object of the machine is to carve an exact fac-simile of the composition model, in hippopotamus or walrus ivory, to constitute the artificial palate to which the teeth are fastened.
As some analogy necessarily exists between Mr. Tomes's machine and that last described, this account will be facilitated by briefly noticing some of the principal points of difference, resulting from the circumstance that Mr. Tomes moves the work about in a vertical plane, and moves the drill in a horizontal plane, and usually cuts the material away by parallel cuts, extended laterally over the surface; whereas in the wood carving machine, it will be remembered the work is horizontal the drill vertical, and the motion rambling in all directions.
Mr. Tomes's tracer and drill are fixed four inches asunder on one slide, that is moved horizontally towards the work by a weight, and pulled back by a lever; and the cement model and the ivory to constitute the copy, are clamped on circular plates or disks, also four inches asunder, and which disks are fitted upon the slide plate of a long horizontal slide, moved by a coarse screw with a winch handle, by the traversing of which the series of lines is usually cut. This horizontal slide is mounted upon a vertical slide, having a screw and ratchet movement, so arranged that when one irregular undulating line of the work has been cut, and the drilling slide withdrawn to its full extent, the work is shifted by the ratchet movement, more or less either upwards or downwards, according to the particular nature of the work, and thus, by a succession of parallel cuts, the entire surface is eventually produced, the weight all along supplying one constant pressure to the slide carrying the drill and tracer, to keep them up to their work with the right degree of force; and from the graduated path of this machine, and its perfection of action, the tool-marks are not discoverable in the finished work, as they become completely merged one into the other.