PLANING MACHINERY. Of late years the increase in the price of hand Labour, and the necessity for securing mathematical accuracy in the surfaces of contact of the parts of machinery, have led to the application of other machinery to the preparation of the surfaces of wood, of stone, and of iron-work. The nature of the various materials has led to modifications of the tools employed, as might naturally have been ex'pected ; and it is worthy of remark that the application of machinery to this purpose has been much more successful with the more apparently intractable and hard materials, stone and iron, than it has been with the softer one, wood. Generally speaking, the tools used for planing wood, or iron, are fixed at a certain height, but are able to reverse the direction of their points ; and the surfaces to be operated upon may be moved horizontally under the tools, so as to be attacked In their alternate motion, or only in one direction when the cutting tools are not susceptible of being reversed. In wood planing machinery the majority of the tools hitherto used in England have a rotary motion ; and from this fact, and from the tendency of the wood to tear up, as the workmen say, it is necessary to finish the best class of joiner's work by hand labour. It may be also stated that until the introduction of planing machinery for iron, it was almost impossible to obtain a large and perfectly level surface on a plate of that metal ; so that in fact this machine has been one of the most important agents in the advance of the arts connected in any way with the use of iron. The success of the application of machinery to the dressing of stone, or of wood, depends, however, solely upon the value of hand Labour; and its introduction becomes a mere question of local economy, whence its more general use in America.
In the iron planing machinery there is a large bed or plate connected with the driving machinery in such a manner as to allow the bed to move alternately to and fro in a horizontal direction; and the tool or chisel is axed in a carrier, so as either to reverse the position of its point when the bed has reached the end of its course, or it is raised on a horizontal pin so as to allow of its being lifted by the projections of the surface operated upon, and thus only to work whilst the bed is travelling in one direction. The distance between the bed and the carrier is regu
lated by a strew; and the width of the face of the tool is varied according to the greater or lesser quantity of iron to bo removed, the finishing tool being wider than the roughing point. A slight burr is left on each side of the path of the tool, which is removed subsequently if a perfectly smooth face should be required. Almost all the tool makers of the present day manufacture these beautiful machines; but those made by Mr. Whitworth are certainly amongst the best, even if they be not the very best, of their class.
Mr. Hunter took out, some years since, a patent for a modification of the iron planing machinery, which hag been applied with such remarkable success by the late Mr. L. F. Carnegie, in his flag stone quarries near Arbroath, that it must remain a matter of surprise that the use of the machine has not been more generally diffused. In Mr. Hunter's stone planing machine the bed moves under a chisel, of a width of face varying inversely with the amount to be removed, as in the case of iron planing engines, and the slight burrs are worked down by hand. The American stone planing machines seem to consist for the most part of rotary cutters of chilled cast iron which wear away by friction the surfaces exposed to their action.
The ordinary descriptions of wood planing machines consist of cutters, or steel plates, working with a rotary motion ; but, as was before stated, they do not leave the finished surface in the state required for good work. The best American machines of this kind, however, have cutters like an ordinary plane iron, screwed to a carrier able to be adjusted over the heard to be upon by means of a screw. In front of each cutter is placed a loose bar as near to the knife as possible, for the purpose of keeping the grain of the wood perfectly close immediately before the knife. For the best description of joiner's work the wood thus planed requires to be finished off with the smoothing plane, as in the case of the wood prepared by the ordi nary jack, or trying planes used in ordinary hand labour. In the latter case the rough work is done by the jack plane ; it is carried to a higher point by the use of the trying plane, and is by the smoothing plane.