PLANING MACHINE, as the term implies, is an engine for effecting, by machinery, the operation of plan ing timbers, boards, &c. Of all the manual perform ances of a carpenter or joiner, there is perhaps no one that is more laborious, that employs more time, or re quires less skill, than that of planing ; and consequently no one, in which a machine may be more advantageously employed to perform the functions of the artist. It is, however, only within a few years that any attempt has been made to produce an engine capable of this kind of operation ; the planing machine of General Bentham, for which he took out a patent in 1791, having been, we be lieve, the very first essay that was ever made; and this was not attended with all the advantage the ingenious pro jector had anticipated. The principal object in this pa tent was to exonerate the joiner from the charge he had of his tool in the operation of planing, by so adjusting the cutting-iron, that it could not but perform the opera tion intended without requiring any of the skill of the workman, and thereby rendering a common labourer equally as serviceable as the best joiner for this purpose. With this view, the plane is made the full width of the boards, and on each side of it are fixed fillets or cheeks, which project below the face of the plane just as much as it is intended to reduce the board in thickness, serving thereby to guide the plane sideways, and to gage its thickness ; because, when the boards are reduced to this amount, the fillets then rest on the bench on which the boards are placed, and will no longer apply its edge to the plank. The plane is kept down by its own or by ad P L A ditional weights when necessary, latter are so con trived as to be capable of having their position shifted during the time the plane is making the stroke, the pres sure at first acting forwards, and lastly on the hinder part, to prevent the fore-end dipping down the instant it leaves the board. By another contrivance, the plane is lifted up on its return, so as to clear the cutting edge from the wood; this is effected by a piece of wood which acts as a handle to the plane, and to which the power is applied; it is placed by this upon an axis extending across the width of the plane, and carrying on each side a short le ver, provided with rollers at their extremities ; the han dle projects upwards from the plane, which, being forced forward by it, assumes an inclined position, as do also the short levers, and their rollers then rise above the cheeks of the plane ; but when the plane is drawn back into an erect position, and the levers moving with it, their rollers project beneath the cheeks of the plane, and raise it off the bench, the plane being on its return borne by them.
The bench for supporting the board during the opera tion, has also some peculiarity in its construction, which it may be proper to describe. In cases where the boards to be planed are winding and irregular on the lower side, so that they will not lie fiat upon the bench, it is provided with two sides that may be brought close upon the edges of the board, and hold it steady between them, being fur nished with two or more rows of fiat teeth to penetrate the wood and retain it; these sides being SO contrived as to rise and fall with the bench to accommodate the whole to different thicknesses of board. When a very thin board is to be planed, it would be liable to spring up to the iron, so as to be reduced even after the plane came to rest with its cheeks upon the bench ; to avoid which, the edges of the board are to be held by the sides of the bench above mentioned ; but as it would still be liable to spring up in its middle part, heavy rollers, or rollers loaded with weights, are fitted in apertures made in the plane, as near as possible to the cutting edge, which answer the intend ed purpose of keeping the board down close to the bench. For planing pieces of greater thickness at one end than at the other, the cheeks of the plane are borne upon rulers of wood, laid on the bench on each side, the wood being as much thicker at one end as the board is to be at the other ; therefore, when the plane has reduced the wood, the cheeks come to their bearing on these rollers, and cause it to move, not parallel to the bench, but inclined according as they are thicker at one end than at the other. In like manner, by using them of different thicknesses at the different sides, the boards may be made what the work men call feather-edged.