Part 7 (1/2)

The _turning-saw_, Fig. 95, is a narrow saw, set in a frame, which stretches the saw tight, so that it works as a tension saw (cf. p. 62).

The best frames are made so that the handles which hold the blade can revolve in the frame. The turning-saw is used chiefly for cutting curves. A 14 inch blade, 3/16 of an inch wide is a good size for ordinary use. The teeth are like those of a rip-saw, so that they are quite likely to tear the wood in cutting across the grain. Allowance should be made for this and the surplus removed with a spokeshave. The turning-saw may be used to cut on either the pulling or the pus.h.i.+ng stroke, with the teeth pointed either toward or away from the worker.

The pulling cut is generally better, as it puts less strain on the frame than the pus.h.i.+ng cut. Both hands should grasp the frame as near the end of the blade as possible, Fig. 95. Turns are made by revolving the frame on the blade as an axis, which should always be kept at right angles to the surface of the board. Care should be taken not to twist the blade.

[Ill.u.s.tration: Fig. 95. Using a Turning Saw.]

[Ill.u.s.tration: Fig. 96. Saw-Vise.]

_To file and set a saw_, the saw is first fastened in the saw-vise, Fig. 96, with the teeth up. It is then top-jointed by running a flat file or a saw-jointer, Fig. 97, back and forth lengthwise along the tops of the teeth to bring them to a level. After jointing the saw should be set. For this purpose a saw-set, Fig. 98, is necessary.

Every alternate tooth is bent in the direction of its set by the plunger in the instrument pus.h.i.+ng against the anvil, which is an adjustable eccentric disc. After the saw is set, it is filed. This is done with a triangular file, Fig. 144, p. 90, which is held in the right hand and its point in the thumb and fingers of the left.

Pressure is applied only on the forward stroke, which should be long and even, the file being raised above the tooth on the return stroke.

The file should cut in the direction of the set, that is, the teeth having the set away from the worker are filed first. Every alternate tooth, 1st. 3d, 5th, etc., is filed, and then the saw is reversed and the other set, the 2nd, 4th, 6th, etc., is filed.

[Ill.u.s.tration: Fig. 97. A Saw-Jointer.]

[Ill.u.s.tration: Fig. 98. Saw-Set.]

In filing a rip-saw the file should move exactly perpendicularly to the plane of the saw blade, that is, directly across the teeth. The filing is done on the back of the teeth, the file just touching the face of the next one. The filing is continued, with one, two, or three strokes, for each tooth, as the case may require, or just until each tooth is sharp.

In filing a crosscut-saw, the file is held pointing upward and toward the point of the saw. The file should cut in the direction of the set. The angle of the cutting edge is determined by the horizontal inclination of the file to the blade; the angle of the point is determined by the perpendicular inclination of the file to the blade.

Finally the sides of the teeth are rubbed lightly with a slipstone to remove the wire edge. It should always be remembered that a saw is an edge tool, and its edges are as liable to injury as any edges.

PLANES.

The _plane_ is a modified chisel. The chief difference in action between a chisel and a plane in paring is this: the back of the chisel lies close down on the surface of the wood that is cut, and acts as a guide; whereas, in the plane, the cutter is elevated at an angle away from the surface of the wood, and only its cutting edge touches the wood, and it is held and guided mechanically by the plane mechanism.

In other words, a plane is a chisel firmly held in a device which raises the cutter at an angle from the work, regulates the depth of the cut, and favors the cutting rather than the splitting action.

An ill.u.s.tration of a chisel converted into a plane is the adjustable _chisel-gage_, Fig. 99.

[Ill.u.s.tration: Fig. 99. Adjustable Chisel-Gage.]

[Ill.u.s.tration: Fig. 100. Wooden Bench-Plane.]

[Ill.u.s.tration: Fig. 101. Section of Jack Plane.]

The plane has developed as follows: it was first a chisel held in a block of wood. This is all that oriental planes are now, simply a sharpened wedge driven into a block of wood. When the hole works too loose, the j.a.panese carpenter inserts a piece of paper to tighten it, or he makes a new block. The first improvement was the addition of a wooden wedge to hold in place the ”plane-iron”, as the cutter was formerly called. In this form, the cutter or plane-iron, tho still wedge-shaped, was reversed, being made heavier at the cutting edge in order to facilitate fastening it in the wooden plane-stock by means of the wooden wedge. Then a handle was added for convenience. Then came the cap, the object of which is to break back the shaving and thus weaken it as soon as possible after it is cut. Until a few years ago, this was all that there was in a plane, and such planes are still common, Fig. 100. Finally there appeared the iron plane, Fig. 101, with it various mechanical adjustments. The following are the parts of the Bailey iron plane:[4]

1. Cutter, or bit, or blade, or _plane-iron_.

2. Cap, or _plane-iron cap_, or curling iron.

3. Cutter screw, or _plane-iron Screw_.

4. Clamp, or _lever cap_, or wedge.

5. Clamp screw, or _cap screw_.

6. _Frog_.

7. _Y Adjustment_.

8. Bra.s.s set screw, or _bra.s.s adjusting nut_.

9. Lever (for _lateral adjustment_).

10. _Frog screw_.

11. _Handle_.