A Course In Wood Turning by Archie S. Milton and Otto K. Wohlers
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Archie S. Milton and Otto K. Wohlers >> A Course In Wood Turning
[Illustration: Fig. 27.]
2. If it is desired to have the twist wind around the shaft twice, draw
circles 1-1', 2-2', 3-3', and 4-4' and the spaces will grow
proportionately smaller at the small end.
3. Draw four lines running lengthwise on the spindle and 90 deg. apart as
shown in the midde figure in heavy lines (Plate B-V--2-b').
4. Begin at A and draw a curved line to where the 90 deg. line crosses
circle 1-1'. From there extend the line to where the next 90 deg. line
crosses circle B-B' at point B'. Continue in this manner until the other
end of the shaft is reached. Begin at A' and draw a line on the opposite
side of the shaft. These two lines running around and along the shaft
form the grooves while the portion in between forms the beads of the
double spiral.
5. Saw to the desired depth, being 1/4" less than half the diameter at
the point where cut. With a chisel or knife form the grooves and beads.
It is necessary to be careful about not ending the grooves too abruptly.
(See point 6 in Plates B-V--1-a, a'.) Smooth with a rasp and sandpaper
while the lathe is revolving slowly.
6. Cut the design on the ends and polish.
PLATES B-V--3-a, a'. DOUBLE GROOVE SPIRAL. STRAIGHT SHAFT
To work out the double groove spiral for the magazine holder
illustrated, proceed as follows:
1. Square up the stock to 1-3/8". Center carefully and turn the design
on both ends as shown, in the upper diagram (Plate B-V--3-a'). Turn the
cylinder between the top and bottom, making it 5-1/2" long and 1-3/8" in
diameter.
[Illustration: Fig. 26.]
2. Divide the cylinder into two equal parts. Each part represents one
revolution of the spiral.
3. Divide each half into four equal parts as shown in the top and center
diagrams (Plate B-V--3-a'), 1-1', 2-2', 3-3' and so on. The proportion
of the distance between these circles should be one-half the diameter of
the cylinder.
4. Draw lines A-A, B-B, C-C, and D-D, parallel to the axis of the
cylinder 90 deg. apart.
5. With a band 3/16" wide of any substantial material (preferably a
narrow strip of tin or a watch main spring) begin on the line A-A at
circle 1, and connect circle 1' at line B-B, and then connect circle 2
at C-C, and so on until the spiral is made the entire length. Mark on
both sides of the 3/16" band so as to keep the spiral parallel.
6. Next begin at the line C-C where circle 1 crosses it and connect from
here to 1' at B-B. Proceed as in Step 5, as shown in the center diagram.
7. Now erase the extreme ends of the spiral near circles 1 and 5, and
deviate from the original spiral and follow the circles in a more
parallel direction so as to allow the spiral to begin and end gradually
and not too abruptly. Refer to the lower diagram for this.
8. Cut out portions of wood between the bands previously marked around,
as shown in the lower figure. The wood should be cut out with a knife so
as to leave the corners sharp on the narrow bands. The portion cut out
should be a semi-circle and can be sanded by making a spindle a little
smaller than the distance between the bands and fastening sandpaper on
the spindle. Place in the lathe and hold the spiral on the sandpaper
cylinder at an angle so that the spiral will fit. Turn gradually and the
sandpaper will smooth up the portion between the bands and true it up.
At the ends where the grooves are smaller, use a smaller stick around
which sandpaper has been wound and work out by hand.
9. It is well to cut straight down, about 1/32" deep, along the lines
marking out the narrow bands. Then the wood will not be so likely to
split while removing the stock which forms the grooves between the
bands.
10. Cut out the mortises in the square portions which have been left at
both ends. Make the frame work for the sides and cane. Glue together and
polish.
Note:--By making the posts smaller and using the same construction for a
side a nice looking book stall may be made. The proportions for the
posts are the same as mentioned in Step 3.
[Transcribers note: There are 142 line art illustrations after this
point in the book. They are all provided in the illustrated HTML
edition of this book.]