getting the handles to
fit true. This is caused by not getting the hole in the head straight.
Turn the head to a cylinder 3/16" larger than the finished dimension.
Then bore the hole perpendicular to the axis as near as possible,
either by leaving it between the lathe centers or by placing it in a
vise. The handle is then fitted into the head. A snug fit is necessary.
If one side "hangs" or is lower than the other the centers are moved
sufficiently to correct it. The head is then turned to exact size and
finished.
A-II--7. Vise Handles.
Turn the spindle with the solid head to dimensions. Bore a hole through
a 1-1/4" square block and fit the block snugly to the end of the
spindle. Turn this block to the same dimensions as the other head. This
method will save chucking the second head and is much quicker.
CHAPTER VI
OVAL TURNING
Oval work as a problem in turning will be found to be a very good one as
well as interesting to the pupil. It brings in the principle of the oval
as used in ordinary shop practice; (arcs from points on the major and
minor axes). For thick heavy ovals the off-centering is very slight,
while for long, thin ones the off-centering is greater. The measurements
given on Plates A-III--1-a, b and A-III--2-a, b will give a good idea of
approximate distances to be used.
While the tool operations are much the same as in other spindle turning
there is one notable difference. The design must be worked out by eye,
because of the nature of the work no caliper measurements can be made
for depth of cuts.
To get the best results the stock of oval turning should be cut square
or slightly rectangular in cross-section and about 3" longer than the
model to be made. The thickness of the stock should be about 1/8"
greater than the major axis of the oval wanted.
The centers are located in the usual manner after which perpendicular
lines are drawn from the sides, passing through the points of the
centers. From the ends of one of these, perpendicular lines are extended
lengthwise of the stock (on opposite sides) meeting the corresponding
perpendicular at the other end of the stock. These lines form the ridge
of the oval. On the other perpendiculars, the points for off-centering
are laid off, measuring the required distance on both sides of the
center point.
With a 1/8" drill bore holes 1/4" deep at each of the off-centering
points as well as the original center. This will insure the lathe
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