The cutting iron having been sharpened, the top-iron is screwed fast at the required distance from the edge, say for coarse works one -sixteenth, and for fine work, one fortieth or fiftieth of an inch. The compound iron is placed in the mouth of the plane, and the eye is directed from the front along the sole, to see that it projects uniformly and the required quantity; the wedge is then put in with the right hand, and slightly tap] with the hammer. If this should by chance carry forward the iron also, a blow on the back of the plane at h, fig. 320, p. 477, drive the iron very small quantity through the sole, and sharpen it by allowing the oilstone to rub both on the edge and on the wood behind; this will produce a very accurate edge, and the iron when set back, will out beautifully.

* When the minute chamfer of the plane-iron is almost parallel with the sole of the plane, it will for a abort time be entirely effective. Thus, as an experiment.

or on the upper surface of the long planes at i, partially withdraws the iron, and in this manner, by a few slight blows on the end or either edge of the iron, and on the end of the wedge, the adjustment is readily effected. Violence should be avoided, as the wedge if overdriven might split the plane, and long before that it would distort the sole and drive the back wood up, which means, that the wood behind the iron would be driven so as to stand slightly in advance of that before the iron, the two parts of the sole becoming slightly discontinuous or out of line. The iron should be always so slenderly held, that one or two moderate blows would release the iron and wedge.

There is a very ingenious modification of the double iron plane,* in which the cutter is a thin unperforated blade of steel placed between a brass bed and an iron top-piece; the cutter, instead of being fixed and adjusted in the ordinary manner by taps of the hammer, is managed by the quiet action of various screws.

In a plane patented in America, in 1832, the bottom or cutting iron is made as usual, but without any mortise; the top iron has a thumb-screw at its upper end, and moves on two lateral pins or fulcrums 3/4-inch from its lower edge; the pins fit into two grooved pieces of metal let into the sides of the plane, the lengths of the grooves exactly determine the situation of the top iron. When therefore the cutter is placed in its required position, the thumbscrew is turned, it bears on the upper part of the cutter, and tilts the top iron, until its lower edge also bears hard against the usual part of the cutter, and thereby fixes it without a wedge.

The main hindrances to the general employment of these constructions appear to be their increased cost, and the great dexterity with which the required adjustments are accomplished by the accustomed hand with the apparently rude, yet sufficient, means of the hammer. †

The planes being respectively in good working condition, the board to be planed is laid on the bench, and if it should be obviously higher, either at the opposite corners from being "in winding," or in the middle, or at the edges from being "cast and rounding" these partial prominences are first removed with the jack plane; but in general the shavings should be of the full length of the work, or at any rate a yard long.

* Invented by Mr. H. Bellingham. See Trans. Soc. of Arts, 1836, vol. li. † The same remark applies to Mr. F. E. Franklin's Screw Bench Hook, (idem, vol. liii,) intended to supersede a or j, fig. 353, page 494.

The toat of the plane is held in the right hand, the front being grasped with the left hand, the thumb towards the workman; the planes require to be pressed down on the work during the cut, this is done less by in exertion of the muscles, than by slightly inclining the body, to cause its weight to rest partly upon the plane. During the return stroke, the pressure should be discontinued to avoid friction on the edge, which would be thereby rounded, and there is just an approximation to lifting the heel of the plane off the work: or in short pieces it is entirely lifted. The general attempt should be to plane the work somewhat hollow, an effect which cannot however really occur, when the plane is proportionally long and quite straight.

The sole of a long plane is in a great measure the test of the straightness of the work; thus when the rough outside has been removed with the jack-plane, the trying-plane is employed, which is set with a much finer cut, and the workman will in a great measure tell the condition of the surface by the continuity and equality of the shavings. It is however also needful to examine its accuracy with a straight-edge; the edge of the plane applied obliquely across the board is in general the primary test, but as the work approaches to perfection, the straight-edge is laid parallel with the sides of the work, and also diagonally across it; and towards the last, the work if small is raised to the level of the eye, or in large pieces, the workman stoops to attain the same relative position.

In using the straight-edge the workman is partly guided by the eye, or the line of light that is observable between the instrument and the work, and partly by the sense of touch, as he tries whether the straight-edge, when it is very slightly rotated as on a center, bears hardest at the ends or in the middle, and he applies the plane accordingly.*

* The straight edge is simply a wide thin bar of wood or metal, made as accurately straight as possible; the truth of a straight-edge can be only proved by the examination of a series of at least three. Thus, supposing A to be perfect, B to be slightly concave, and C to be slightly convex; it might happen that B and C exactly agreed, but A could not agree with either of them.

Or supposing A to be concave exactly like B, or to become B', then B and C

The foregoing mode refers to surfaces of moderate width, but when the pieces are narrow, or two or more distant parts alone are required to be in one level, the winding sticks are employed. These are two straight-edges, say twenty to thirty inches long, which are placed transversely upon the ends of the work and parallel with each other, they receive their direction from the respective ends or transverse sections, and should these be inclined to each other, or in winding instead of parallel, the winding sticks would magnify the error. This is explained by the diagram fig. 354, the eye placed on the level of the imaginary plane, bounded by the edges a b, c d, of the winding sticks, would find the edge of a b exactly parallel with that of c d, but if c d were situated as in the dotted lines, the disagreement of position arising from the twist or inclination of the edge would be immediately apparent. It is important that the winding sticks should be parallel, as then the eye may be directed to their upper edges, thereby avoiding the interference of the work itself. If the work be perfect, the two sticks appear in exact parallelism, when from the foreshortening, c d, is nearly eclipsed.