LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
Spindle speeds for drills and other rotating cutters can be determined using
the same formula by substituting the cutter diameter of the drill or cutter
for the diameter of the workpiece. Table 2 on page 49 may be used to save
time when computing rotational spindle speeds for common cutting speeds and
common workpiece diameters.
(d) Another factor to consider when selecting cutting speed includes the
use of cutting oils, the length and diameter of the workpiece, and the
condition of the lathe. If a large stream of proper cutting oil is applied
to the workpiece at the cutter bit, the cutting speed can be increased as
much as 40 percent.
If the diameter of the workpiece is small and its
length is great enough to set up vibrations due to the speed, a poor finish
will result; to correct this condition, the speed must necessarily be
reduced. The lathe may also be in poor condition so that high speeds will
cause harmful vibrations.
(e) The technical manual for the lathe being used should be consulted
for instructions in setting spindle speed for operation.
If a desired
spindle speed is not available on the lathe, select a speed nearest that
which is desired, generally the first slower speed that is available. For
efficient lathe operation, the machinist should be able to recognize too
slow a speed as well as too fast a speed.
(3) Feed.
(a) General.
Feed is the term applied to the distance the cutter bit
advances for each revolution of the workpiece. Feed is specified in inches
per revolution. Since the best feed depends upon a number of factors such
as depth of cut, type of material, size of workpiece, and condition of the
lathe, it is difficult to list the best feed for the different materials.
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