The modern iron plane, illustrated in Fig. 22, can now bo bought in a great variety of sizes and styles. These planes, with their true and unchanging faces, and their simple appliances for setting and adjusting the cutter (or plane-iron) to the face of the plane and to the required thickness of shavings, are greatly to be preferred to the old-style wooden planes. The general construction of the iron plane will be readily understood from Fig. 23, one side of the plane being removed to show the arrangement of the parts; a is the cutter, or plane-iron, which is made of the best cast steel and of equal thickness throughout. In all new planes this part will be found ground and sharpened for immediate use.
The cap-iron f (Fig. 23) is fastened to the plane-iron, by an adjusting screw, as shown in Fig. 24. For whetting or grinding the cutting edge, it is not necessary to remove the cap-iron but only to loosen the connecting screw and to slide the cap back to the extreme end of the slot in the plane-iron, tightening it there by a turn of the screw. The cap-iron will then serve as a convenient handle or rest in whetting or in grinding.
The iron lever c (Fig. 23) is held in place below its center by the screw g, which acts as a fulcrum, and the lever is readily clamped down upon the irons by the use of the cam-piece d. When this cam is turned upward it ceases to bear upon the irons. The lever c may then be removed from its place, and the irons released, without turning or changing the adjustment of the screw g, as the lever and irons are properly slotted for this purpose.
Should the pressure required for the best working of the plane-iron need changing, it can easily be obtained by tightening or loosening the screw g.
When the plane-iron is secured in its place, the use of the brass thumb-screw b will draw or drive the plane-iron; and thus the thickness of the shaving to be taken from the work can be regulated with perfect accuracy. By the use of the lever e, located under the plane-iron, and working sidewise, the cutting edge can easily be brought into position exactly parallel with the face of the plane, should any variation exist when the iron is clamped down. To ascertain this, hold the plane up, and look down over its face; the greater projection, if there be any, of one or the other of the corners of the iron, can readily be seen.
The cap-iron f, which is not sharp, is not, as is often supposed, used for the purpose of strengthening or stiffening the cutting iron, but as a chip-break to prevent the cutting edge of the plane-iron from chipping, tearing, and breaking the grain of the wood below the surface when the grain turns and twists, or when it is knotty and crooked. In such cases the tendency of the plane-iron is to split and tear out the fibres of the wood in front of the cutting edge. To avoid this, the cap-iron is screwed on with its dull edge quite close to the cutting edge, so as to bend and break off the fibres or the shavings before the split gets fairly started below the surface.
The cutting edge of the plane-iron is said to have lead in proportion to the distance it is placed in advance of the dull edge of the cap-iron. The depth of the splits, or the roughness of the cross-grained surface, will be just equal to the lead of the cutting edge. For soft, straight-grained wood, the lead may be 1/32 inch or even more, but this must be reduced in proportion as the wood is curly, cross-grained, or knotty.
The grinding, or the whetting, must always be done on the bevel side only of the plane-iron, the upper side being kept as flat and as smooth as possible to secure easy working.
All plane-irons should be ground slightly rounding to the extent of the thickness of a thin shaving. This rounding of the cutting edge should bo the true arc of a circle throughout the entire length of the cutting edge, and not simply a rounding-off of the corners as is sometimes directed. Rounding the edge to the extent of the thickness of a shaving will prevent the plane-iron from grooving into, or plowing out a wide groove in, the surface that is being workcnl, and will also assist greatly in working the edges of the piece to right angles, or square with the face side. To do this it is not necessary, should one corner of the edge be higher than the other, to tilt the plane on the high edge, but, while holding it flat and firm on the surface of the edge being planed, push the plane sidewise towards the highest corner in order to reduce that corner. This will readily be understood when we remember that the cutting edge of the iron is rounding. If the plane is held so that the middle of the plane-iron will do the cutting, the shaving planed will be of the same thickness on both edges; but if the plane is pushed over to one side, either to the right or to the left, the shaving will be feather-edged, or thick on one edge and thin on the other, thus reducing the higher corner of the edge of the piece.
When the plane is to be used, the beginner should first carefully adjust it to the thickness of shaving required, by holding it up and looking down over the face of the plane, when the projection of the plane-iron can readily be seen, and then by testing on the piece to be planed.
The operator's position should be one of perfect ease, standing well back of the piece to be planed, and pushing the plane to aim's length from (not alongside of) the operator, taking long and continued shaving3 from the board. When starting the shaving at the end of the board, care should be taken to hold the forward end of the plane down firmly, or the act of pushing it forward w cause that end to tilt of and the plane-iron to chatter on the surface as it begins to cot the shaving. This is owing to the fact that nearly two-thirds of the plane overhangs the end of the board, requiring firm pressure on the forward end to balance it while the stroke is being started.
" To insure smooth work, care must be taken to plane with the grain of the wood, and not against the ends of the fibres as they lie in the surface of the board. - Should the fibres tear out and the surface become rough, reverse the ends of the boards bo as to cut the shaving in the opposite direction, and note the difference in the effect on the planed surface.
Of iron planes, the most important is the No. 6 Jack plane, 14 inches long, and having a cutter 2 inches in width. This plane is illustrated in Fig. 25. When the pattern lumber has first been roughly planed in a planing mill, this No. 5 plane almost exclusively can be used for planing and pattern making. In making or in "truing up" very large surfaces, however, or in making long glue joints, the No. 7 jointer plane, 22 inches long and having a cutter 23/8 inches wide, will be found necessary, This plane is shown in Fig, 22, and differs from the jack plane only in its length and in its extra width of face.
For mahogany or other hard wood, the No. i smooth plane, illustrated in Fig. 26, will be found very useful. This plane is made in several sizes. The No. 4, which is 9 inches long and has a 2-inch cutter, is the best size for general use.
Next in importance to the three planes already mentioned, is the block plane, illustrated in Fig. 27. The No. 19, which is 7 inches long and has a cutter 1| inches wide, is the most desirable for the pattern maker's use. It has an adjustable throat, as well as the screw and lateral lever adjustments of the other planes. This plane has the advantage of being so constructed as to be held easily in one hand. Owing to the low angle at which the cutter is placed it works more smoothly and easily on end wood and on miters than any other plane. In cases where lumber must be dressed from the rough, without being first roughly dressed in a planing mill, the No. 40 scrub plane, illustrated in Fig. 28, will be almost indispensable. It is 9½ inches long, and has a cutter 1¼ inches wide. The cutter is a single iron, and is ground and sharpened very rounding on the cutting edge, as shown in Fig. 28, to allow of cutting a very thick shaving without grooving at the edges. This plane works rapidly and easily, preparing the rough-sawn surfaces of planks for the finishing planes.
For truing and smoothing circular arcs and curves of all kinds, either convex or concave, there is no tool that equals the circular plane, illustrated in Fig. 29. This plane has a flexible steel face which can easily be shaped to any required arc or curve by turning the knob on the front of the plane.