PLANING MA(1311INE, a machine used to diminish the great manual labour of planing the surthces of planks and boards of wood : in strictness, those alone should be termed planiug machines, which reduce the surface of the wood to a true and smooth plane, by means of planes, or instruments of a similar nature, though actuated by the power of machi nery instead of the strength of a man's arm; but custom has denominated those machines which cut flat surfaces in a different manner from planes, by the same name.
These machines are of modern invention; the first, we believe, was projected by General Bentham, who obtained a patent for it in 1791. It consisted of a plane, to be put in motion by means of a crank turned by a mill, to give it a motion; or, on a smaller scale, it might be worked by hand in the usual manner, but the plane was so formed as to require none of the skill and attention sary in the ordinary method of operating. The plane is made the full width of the boards intended to be planed, and on each side of it fillets, or cheeks, are fixed, which project beneath the face of the plane just as much as the thickness the board is to be reduced to : these cheeks, therefore, guide the plane sideways in passing along the board, and gauge it in thickness; because, when the board is reduced to the quantity that the cheeks are beneath the surface of the plane, the cheeks rest upon the bench, or surface, on which the board lies, and bear off the plane, so that it can cut no longer. The plane is kept down by its own weight, which is increased, when necessary, by loading it with weights, and these are contrived to be capable of shifting their position from one end of the plane to the other during the time it is making the stroke ; because, at first, the pressure is required at the fore end to enter the cut, but, at the conclusion, it must be tripping at the hinder end, to prevent the fore end trippin down the instant it leaves the board. By another contri vance, the plane is caused to rise up sufficiently to clear the edge from the wood when the plane is on its return. It is by a piece, which acts as a handle to the plane, and to which the power is applied, that it is fixed in the manner of a lever upon an axis extending across the width of the plane, and carrying at each side thereof a short lever, provided with rollers in their extremities ; the handle projects upwards from the plane, which being forced forwards by it, assumes an inclined position, as do also the short levers, and their rollers then rise above the checks of the plane ; but when the plane is drawn back, its handle is first drawn back into an erect position, and the levers moving with it, their rollers project beneath the cheeks of the plane, and raise it oil the bench, the plane being in its return borne by them.
The bench for supporting the board during the operation, was also of a peculiar construction, in order to confine the work steady upon it. In cases when the boards to be planed are winding or irregula• on the lower side, so that they cannot lie fiat upon the bench, it is provided with two sides, which can be brought to close upon the edges of the board, and hold it steady between them, being furnished with one or more rows of flat teeth, to penetrate the wood and retain it ; these sides are contrived to rise or Ell upon the bench, to accommodate the different thicknesses of the hoards. When a very thin board is to be planed, it might 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 this, the edges of the board are to be held by the sides to the bench before-mentioned,but as it would still be liable to spring up in the middle part, heavy rollers, or rollers loaded with weights, are fitted in apertures made in the plane as near as possible to the and these will keep the board a down close upon the bench. For planing pieces of greater thickness at one end than the other, the cheeks of the plane are to be 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 intended to be thinner at that end ; therefore, when the plane has reduced the wood, the cheeks come to bear upon these rulers, and cause it to move not parallel to the bench, but inclined, according as they are thicker at one end than the other ; in like manner, by using them of different thicknesses at the different sides, the boards may be made feather-edged.