ameter. 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 spaces 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 spaces 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 space
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 deg. 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.

[Illustration: 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.

[Illustration: Fig. 24.]

[Illustration: Fig. 24-a.]

[Illustration: Fig. 25.]

8. Cut the design on both ends of the cylinder and polish.

PLATES B-V--2-a, a', a''. SINGLE SPIRAL. TAPERED SHAFT

To lay off a single spiral for the electric lamp shown in Figs. 24 and
24a proceed as follows:

1. Select your wood and bore a hole through it. Plug the hole and center
the piece in the lathe. This insures getting the hole exactly in the
center, and it will not be cut into while t