CHAPTER IX.

PLANING AND MOULDING MACHINES-continued.

FOLLOWING Bramah's patent, several improvements were introduced by Burnett, Paxton, Poyer, and others; but it was not till the year 1827 that planing machines were brought into extended practical use in this country. In this year Mr. Malcolm Muir, of Glasgow, invented and patented a machine of most improved construction. Its mechanism contained many of the most essential points as in use in planing machines of the present day; in fact, succeeding makers, although introducing modifications of their own, seem to have entirely accepted it as their model. As its invention is of great interest to engineers, and marks an era in wood-working machinery, we give an illustration of Muir's first machine, with a description of it as given by Hebert.

"This machine, invented by Mr. Muir, of Glasgow, has for its object the preparation of complete flooring boards with extraordinary despatch, and in the most perfect manner; the several operations of sawing, planing, grooving, and tongueing being all carried on at the same instant, by a series of saws, planes, and revolving chisels.

'Fig. 8 represents a plan of the machine, slightly

modified, to render the construction more easily understood by the reader. The machinery is adapted for the simple planing of boards, as well as the preparation of square-jointed or plain-jointed flooring. We shall commence our description by an account of those parts which constitute a simple planing machine, and then proceed to describe the apparatus by which it is adapted to the preparation of jointed flooring. The planing machine consists of a perfectly flat and straight bench d dd, which should be at least twice as long as any board intended to be prepared upon it. This bench is made fast to a block of stone cc or other solid matter, which, together with a suitable framing, serves to keep the machinery as firm and steady as possible. Along one side of this bench is a raised guide e e, which extends as far as the circular saws i, i; but only a part of it is shown in the figure, in order to bring some other arrangements more into view. About the middle of the bench a metallic plate a a is let in flush with its surface, which forms a durable stock for the plane irons; these plane irons are of the usual form, but of greater breadth than the boards to be planed. The projection of their cutting edge is effected and regulated by screws, and the number of plane irons employed at a time is determined by the degree of finish required for the surface of the boards; three plane irons are, however, generally used, as shown at h, h, h, the dark spaces being the mouths of the planes; from this it will be seen that it is the lower side of the board that is planed, and the shavings are delivered under the machine. An endless pitched chain, having catch hooks at convenient distances, takes hold of the boards as they are put into the machine in succession,

and drags them along the bench; the edge of one of the sides of each board passing under a rebate in the

FIG. 8.-PLANING MACHINE PATENTED BY MUIR, A.D. 1827. guide or fence (as shown in the figure) prevents the board from bending upwards by the action of the chain,

G

while it is pressed down to the plane irons by springs or weighted levers, as seen at b, b, which are mounted upon antifriction rollers, the axles of which are so inclined as to cause the boards to be uniformly driven against the fence and to pass in a straight line through the machine. Motion is given by a band from a large revolving drum, placed above the machine (not shown. in the figure), which communicates with the drum u, upon the shaft of which is a pinion that drives the toothed wheel j; the axis of the latter carries the pitched rigger t, round which the endless chain is passed, and stretched in a parallel direction with the bench, by passing over the pulley z, at the opposite end of the machine; at this place only a small piece of the chain is brought into view, as the introduction of the whole of it would hide or tend to confuse some of the other parts of the apparatus. The pulley z is mounted upon a tightening frame y which moves upon a joint at the lower end, the tension being increased or lessened by the wedges 1, 1, or by regulating screws. The parts we have thus described constitute a separate machine for the planing only of boards. For the preparation of plain or square-jointed flooring boards, the following additional apparatus is brought into operation. A part of the fence e is slightly hollowed from the direct line of the bench, to admit of projecting inequalities in the edges of the boards; these are removed by irons or cutters fixed on a horizontal revolving plate f, the periphery of which enters an aperture in the fence e; and it is on the edge of the board presented to this side of the machine that a tongue or feather is formed when required. To produce this effect two circular saws, g and h, are used,

one of which, g, revolves under the board, and cuts it upward; the other, h, revolves above the board, and cuts it downwards, to such a depth only on each side as to leave a tongue or feather of the required thickness uncut. By the progressive motion of the board it next passes under the operation of two circular saws i, one only of which can be seen, as the other is directly underneath on the same spindle, and separated only by a ring or washer, which is of the same thickness as the tongue. These saws, acting horizontally, or at right angles to those at g and h, cut off the superfluous wood, and leave the tongue projecting from the board completely formed. The opposite edge of the board is cut parallel to the other by a circular saw k revolving vertically, which is called the "breadthing" saw; a guide fixed to the head of o, which supports the spindle of this saw (but which cannot be seen in the figure), is so placed as to conduct the superfluous pieces, separated from the boards by the saw k, underneath the circular saw ; the slips are thus removed out of the way of the latter saw and preserved. The saw I revolves horizontally, and is called the "grooving saw;" it is considerably thicker than ordinary circular saws, and has long teeth to admit of their receiving a "set" to cut out the whole of the required groove at one operation. The spindle head which carries the grooving saw is adjusted and fixed by screws to a bracket attached to the head o, the latter being placed in slides, which keep it steady, and conduct it in a parallel direction when moved to or from the bench. All the parts that operate on this edge of the board being thus connected, advance or recede together. This movement is effected by means of a screw fitted with collars to the fixed