A Course In Wood Turning Part 6

Place the 3/4" gouge on the rest with the handle parallel to the bed of the lathe. Roll the gouge on its edge and swing the handle so that the grind is perpendicular to the stock with the nose of the tool as the cutting point.

[Ill.u.s.tration: Fig. 20.]

Force the gouge forward into the wood. As soon as the cut is started, the handle is lowered and swung to the left; (if cutting the left side of the concave) at the same time the tool is rolled back toward its original position. This movement brings the cutting point farther down on the lip and the grind, resting on the side of the cut, will force the gouge sidewise and will form one-quarter of the circle. Fig. 21.

[Ill.u.s.tration: Fig. 21.]

This cut is continued from alternate side until the concave is nearly to size. The cut should be tested with a templet before the finis.h.i.+ng cut is taken.

B-I--6-a. Convex Cuts

Rough out the stock between the beads with a parting tool.

Hold the edge of the gouge on the rest with the handle, parallel to the bed of the lathe, to make the nose the cutting point.

Swing the handle to the left so that the grind will form a tangent to the bead at its highest point.

The gouge is then forced into the stock and to the right; at the same time the handle is swung to the right; keeping the grind tangent to the bead at the point of contact. Fig. 22. This cut is continued until the base of the bead is reached.

B-I--7-a. Combination Cuts

As in spindle turning, a combination exercise should be given at this point to provide an opportunity for studying out the best methods of working the various cuts just described into a finished product.

USE OF Sc.r.a.pING TOOLS

When sc.r.a.ping is to be employed, it should be done with only those tools that are made for that purpose, i.e., Square Nose, Round Nose, Spear Point, Right and Left Skew. The handling of these tools will be found easy. The only point to remember is that they should be held flat on the tool rest and parallel to the bed of the lathe when in use.

In general practice the ordinary skew chisel should not be used as a sc.r.a.ping tool, for the cutting edge is not sharpened to withstand the heavy strain required by such work. Should it be necessary, however, to use a skew chisel as a sc.r.a.per, the tool should be held so that the top grind is parallel to the bed of the lathe while in use.

INTERNAL BORING

In roughing out the center for Napkin Rings, Jewel Boxes, etc., the quickest method is to work it out with a small gouge.

Place the gouge on the rest parallel to the bed of the lathe, having the point even with the center of the stock.

Force the gouge into the wood until a hole is bored to the depth required. If the hole is deeper than 1", remove the tool often and clear out the shavings in order not to burn the point.

In order to enlarge the hole to the proper size the point of the gouge is pressed against the left side of the hole a little above the center and a shearing cut is taken. To obviate the danger of the tool catching, all cuts should start from the back of the hole and proceed toward the front.

[Ill.u.s.tration: Fig. 22.]

B-III--8-a. Sphere

After the sphere is turned as nearly perfect as is possible when working between centers (Steps 1 to 4) it is cut free from the waste stock and is centered in a chuck.

The chuck is made of any soft wood and should be cut in the end grain, which will insure equal pressure on all sides. Equal pressure cannot be obtained if the Chuck is cut in cross grain wood, owing to the tendency of side grain to give more than the end grain. The sphere should be forced into the chuck with slightly over half protruding. Very thin cuts should be taken and the sphere should be revolved one-quarter turn after each until true. As the sphere becomes smaller during the cutting, it will be necessary to cut the face of the chuck down and bore the hole deeper and smaller in order to keep more than half of it protruding at all times.

[Ill.u.s.tration: Mirror (See Pages 299-301).]

To remove the sphere tap the chuck lightly with a hammer just above it, at the same time pull out on the sphere.

CHAPTER XI

SPIRAL TURNING

Spiral turning is a subject that has received very little attention by most schools in which wood turning is taught. Spiral work is seen in antique furniture and also in the modern furniture of the present day.

It seems that it takes the wheel of fas.h.i.+on about a century to make a complete turn, for what our forefathers neglected and destroyed the people of the present day value and cherish.

Spiral work gives excellent practice in shaping and modelling wood. It brings into play the principle of the helix as used in cutting threads, etc.; and its form, size and shape may be varied according to the taste of the individual. As in threads so in spiral work we have single and double spirals, and their form and proportion depend upon their use and application in furniture making. A variation of the spiral may be made in several ways: First, by changing the number of turns of the spiral on a straight shaft; second, by running a spiral on a tapered shaft; third, by changing the shape or form of the spiral itself; and fourth, by making more than one spiral on a shaft. It is uncommon to see ten or twelve spirals running around a single shaft.

Some of the forms of the above types are fully taken up and explained in the work that is to follow.

PLATES B-V--1-a, a'. SINGLE SPIRAL. STRAIGHT SHAFT

To work out a single spiral for a pedestal proceed as follows:

1. Turn a cylinder 2-1/4" in diameter. Make the ends slightly larger in order that the design may be turned on each, after the spiral has been worked out.

2. Lay off s.p.a.ces 2-1/16" apart on the cylinder while the spindle is turning in the lathe and divide each of these into four equal parts.

Each one of these large s.p.a.ces represents one turn of the spiral. A good proportion is slightly less than the diameter of the cylinder; thus the diameter of the cylinder equals 2-1/4" and the width of the s.p.a.ce 2-1/16".

3. On the cylinder parallel to the axis draw lines A-A B-B C-C D-D.

These lines should be 90 apart as shown in the top diagram (Plate B-V--1-a'). Line D-D is on the other side of the cylinder as shown in the top and middle diagrams.

[Ill.u.s.tration: Fig. 23.]

4. Start on line A-A at point X, circle 1, and draw a line connecting it with line B-B on circle 1'. Then connect B-B on circle 1' with C-C on circle 2 and so on until a spiral has been drawn the entire length of the cylinder. This line will form the ridge of the spiral as shown in the middle diagram.

5. Next begin on line C-C at circle 1, and draw a line connecting it with D-D on circle 1' then to line A-A on circle 2, and so on as before.

This spiral represents the center of the groove or the portion which is to be cut away. This is not shown in the diagram because more or less confusion would be caused with the line representing the ridge of the spiral.

6. Begin on line C-C at circle 1, and saw to a depth of 3/4". Saw the entire length of the cylinder leaving about 1-1/2" at the ends. Do not follow the line here, but switch off gradually and follow circles 1 and 15, so as to allow the spiral to begin and end gradually and not abruptly.

7. Rough out with a knife or chisel by cutting on both sides of the saw cut. Then use a wood rasp to finish shaping out the spiral. When properly shaped out allow the lathe to turn slowly and smooth with sandpaper by following the spiral as the lathe turns.

[Ill.u.s.tration: Fig. 24.]

[Ill.u.s.tration: Fig. 24-a.]