Modern Machine-Shop Practice Part 203

[Ill.u.s.tration: Fig. 2727.]

[Ill.u.s.tration: Fig. 2728.]

Planes are also made with the sole and the cutting edge of the blade made to conform to the shape of the work. Thus Fig. 2727 represents a rabbeting plane, and Fig. 2728 a side rabbet plane. The latter is, however, very seldom used, but is especially useful in planing hard wood cogs fitted to iron wheels, or the teeth of wheel patterns or other similar work. For ordinary use, it is sufficient to have two, a 3/4 and a 1-1/4 inch, and two or three having a flat sole for flat bottom grooves.

What is known as a core box plane has its sole at an angle of 90, or a right angle; the principle of its action is that in a semicircle the angle is that of 90.

[Ill.u.s.tration: Fig. 2729.]

[Ill.u.s.tration: Fig. 2730.]

In Fig. 2729, for example, it is seen that if a right angle be laid in a semicircle so that its sides meet the corners of the same when revolved, its corner will describe a true circle; hence at each plane stroke the plane may be slightly revolved, to put on the cut, which must be very light, as the core box plane is only suitable for finishing purposes.

For planing across the end grain of wood, what are termed block planes are used, the angle of the blade to the sole being from 65 to 85 degrees, as shown in Fig. 2730, which represents the Stanley iron frame block plane. In block planes the bevel that is ground to sharpen the blade is placed in front and therefore meets the shaving instead of the flat face as in other planes.

[Ill.u.s.tration: Fig. 2731.]

[Ill.u.s.tration: Fig. 2732.]

Fig. 2731 represents the Stanley bull-nose rabbet plane for getting close into corners, and Fig. 2732, a block plane, in which the blade may be set in the usual position or at one end of the stock as denoted by the dotted lines.

[Ill.u.s.tration: Fig. 2733.]

[Ill.u.s.tration: Fig. 2734.]

For fine work planes having an iron body are much preferable to the wooden ones, and in the improved form of planes there is provided a screw mechanism, whereby the blade may be set much more accurately and easily than by hammer blows, such as are necessary with ordinary wedge-fastened blades. Thus Fig. 2733 represents Bailey's patent adjustable planes, the handles only being of wood. The blade is secured by a simple lever movement, and is set by means of the thumb screw shown beneath and behind the blade. The metal stock possesses several advantages, such as that the sole keeps true, the mouth does not wear too large, as is the case with wooden planes. Planes are also made having a wooden body and an iron top, the latter containing the mechanism for locking the blade and setting it quickly. Fig. 2734 represents one of these planes.

[Ill.u.s.tration: Fig. 2735.]

Figs. 2735 to 2744 represent a combination plane. Fig. 2735 is a side, and Fig. 2736 a top view of the tool as a whole.

Pieces A and B form the body of the plane, between which the bits or all the tools are carried except the slitting knife, which is carried by A alone.

In the figures T is a beading tool shown in position, having a bearing or seat in both A and B so as to support it on both sides, and being locked in position by the thumb-screw C. At G is a depth gauge which is moved over into the hole at D, when that position is most suitable for the kind of work in hand. Piece B is made adjustable in its distance from A so as to accommodate different widths of bits by sliding it on the arms M, securing it in its adjusted position by the set-screws S.

Similarly the fence F slides on arms M, and is secured in its adjusted position by the set-screws H, thus enabling it to regulate the distance from the edge of the board at which the bits shall operate, and also guiding the bits true to the edge of the board or work. F is provided with an upper pair Q, and a lower pair R of holes (as seen in Fig. 2737) so that it may be set on the arms M at two different heights as may best suit the nature of the work. In Fig. 2736 it is shown with arms M pa.s.sing through the lower pair of holes. The points of the set-screws H meet the bores of both pairs of holes and therefore lock F to the arms, whether the upper or lower holes are upon the arms. For rabbeting and fillister work the upper holes Q are used, while using ploughs the lower ones are brought into requisition.

[Ill.u.s.tration: Fig. 2736.]

[Ill.u.s.tration: Fig. 2737.]

[Ill.u.s.tration: Fig. 2738.]

[Ill.u.s.tration: Fig. 2739.]

[Ill.u.s.tration: Fig. 2740.]

At W, Fig. 2735, is a spur for cutting the end grain of the wood in advance of the bit, as is necessary in dado and other across grain work, the construction of the spur is seen more clearly in Fig. 2738. The pieces A and B are provided with a recess having four arms or branches, while the spur itself has but three, so that the spur may be set as in Fig. 2735 and be out of action, or its screw being loosened it may be given a half-turn, so that one of its arms will come below B as at X in Fig. 2738. The cutting edges of the spur come exactly flush with the outside faces of A and B, and the bits are so held in their seats that their edges also come flush with these outside faces, which therefore act as guide to the bit; thus Fig. 2739, shows a beading bit in position, and Fig. 2740 a section of work finished, A and B being in section. Fig. 2741 shows a plough in position on the work, A and B being shown in section. It is seen that their inner edges being bevelled, will in using a beading tool, act as a gauge regulating the thickness of shaving taken at each plane stroke, which will equal the depth to which the bit edge projects beyond the bevels of A and B. Similarly in grooving or ploughing the amount to which the bits project below the lowest edges of A and B regulates the thickness of the shaving, and as A and B follow the bit into the work, the blade being once set requires no further attention, the depth gauge regulating the total depth of tool action.

[Ill.u.s.tration: Fig. 2741.]

[Ill.u.s.tration: Fig. 2742.]

[Ill.u.s.tration: Fig. 2743.]

[Ill.u.s.tration: Fig. 2744.]

This principle of the side pieces entering the work with the bits and being adjustable to suit various widths of bits, gives to the tool a wide range of capacity. Fig. 2742 represents the tool arranged for slitting thin stuff into parallel slips, the piece B being removed. The depth gauge is not shown in figure, because it would hide the slitting knife from view, but it is obvious that it would rest on the surface of the work and thus steady the plane. Fig. 2743 is an example of a number of operations performed by this one tool. For tonguing, the bit shown in Fig. 2744 is employed, the depth gauge _g_ being adjustable in the groove by means of the slot shown.

CHISELS.--The princ.i.p.al kinds of chisels are the paring chisel which is used entirely by hand, and the firmer chisel which is used with the mallet. The difference between the two lies in the shapes of their handles, and that the paring chisel is longest. A paring chisel worn to half its original length will serve for a firmer chisel, because when so worn it is long enough for the duty. A chisel should not, however, be used alternately as a paring and a firmer chisel, because the paring chisel requires to be kept in much better condition than the firmer chisel does. Mortice chisels are made thicker than either the paring or the firmer because of their being longer and requiring rougher usage. It is necessary to have several sizes of chisels, varying in width from an eighth of an inch to one and a half inches.

[Ill.u.s.tration: Fig. 2745.]

[Ill.u.s.tration: Fig. 2745_a_.]

[Ill.u.s.tration: Fig. 2746.]

Fig. 2745 represents the form of handle for a paring chisel, its total length being 6 inches, and from A to B being 1-1/2 inches. The diameter at C is 1-1/2 inches, the hollow below D of 3/8 of an inch radius, the diameter at D 1 inch, and the length from B to E 1-1/2 inches. This form affords a firm grip to the hand, the end E being applied to the operator's shoulder. The shape of handle for a firmer chisel is shown in Fig. 2746.

Chisels require great care both in grinding and oilstoning them, being held very lightly upon the grindstone when finishing the grinding so as to avoid as far as possible the formation of a long feather edge. The flat face of the chisel should never be ground, as that would make it rounding in its length, hence there would be nothing to guide it in cutting straight and the value of the tool would be almost destroyed.

In oilstoning the chisel, great care is necessary in order to avoid forming a second facet at a different angle to that at which it was ground, because such a facet is too narrow to form any guide whereby to move the chisel in a straight line, and the consequence is that the edge is oilstoned rounding and cannot do good service. The whole length of the ground facet or bevel should rest on the oilstone, but the pressure should be directed mainly to the cutting end so that at that edge the oilstone will entirely remove the grinding marks, which will, however, remain at the back. If there is at hand a grindstone of sufficiently small diameter, the chisel may be made hollow on the bevel, as shown in Fig. 2745_a_, so that when laid on the oilstone the bevel will touch at the back and at the end only, and this will enable the chisel to be pressed evenly down on the stone, thus producing a very even and flat edge, while leaving but a small area to be oilstoned.

The motion of the hands should not for the oilstoning be simply back and forth, parallel with the oilstone length, but partly diagonal, which will a.s.sist in keeping the chisel level. The back of the chisel should be laid flat upon the oilstone and moved diagonally, under a light pressure, which will remove the wire edge, which may be further removed by lapping the chisel on the operator's hand.

[Ill.u.s.tration: Fig. 2747.]

Chisels for turning work in the lathe are best if made short, and to enable the cutting edge to get up into a corner, the chisel is sometimes given two cutting edges, as at A, in Fig. 2747, the edges forming an angle, one to the other, of less than 90. For finishing curves in the lathe the chisel shown at B in the figure is employed, or for deeper work, as in the bores of holes, handles are dispensed with, chisels being formed as at C and D in the figure.

Gouges, like chisels, are made "firmer and paring," the distinction being precisely the same as in the case of chisels.

When the bevel is on the outside or convex side of the gouge it is termed an outside, while when the bevel is on the inside or concave side it is termed an inside gouge.

[Ill.u.s.tration: Fig. 2748.]

Fig. 2748 represents an outside firmer gouge. The inside gouge may be ground a little keener than the chisel, and requires great care in grinding, because it must be held on the corner of the grindstone, which is rarely of the desired curve. In oilstoning the concave side of a gouge an oilstone slip is employed, the gouge being held in the left hand and the slip in the right, the latter being supplied with clean oil.

The convex side of an outside gouge should be made level on the face of the oilstone, and while the gouge is moved to and fro its handle must be revolved so as to bring all parts of the curve in contact with the oilstone. The small amount of surface on the gouge in contact with the grindstone makes it very liable to have a long feather edge, hence it must be very lightly pressed to the stone, and the same remark applies to the oilstoning in order to reduce the wire edge.

[Ill.u.s.tration: Fig. 2749.]

Fig. 2749 represents a gouge for lathe work, its handle being made long enough to be held in both hands and used as described with reference to turning with hand tools.

Another tool, very useful to the pattern-maker, is the skew chisel, which is also described in connection with hand turning.

SAWS.--There are two princ.i.p.al kinds of saws, the rip saw for cutting lengthwise of the grain of the wood, and the cross-cut saw for cutting across the grain. In shaping these saws the end to be obtained is to enable them to sever the fibre of the wood in advance of the effort to remove it from the main body.

[Ill.u.s.tration: Fig. 2750.]

[Ill.u.s.tration: _VOL. II._ =THE ACTION OF SAW TEETH.= _PLATE XIII._