Tc 9-524 fundamentals of machine tools

7-39

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TC 9-524
Alternatively, 1 inch can be drawn out on the workpiece.
The dial indicator will indicate the taper for that 1 inch and, if
needed, the tailstock can be adjusted as needed to the precise
taper desired. If this method of checking the taper is not used,
then an extensive trial and error method is necessary.
To cut the taper, start the rough turning at the end which will
be the small diameter and feed longitudinally toward the large
end (Figure 7-64). The tailstock is offset toward the operator
and the feed will be from right to left. The tool bit, a right-
hand turning tool bit or a round-nose turning tool bit, will
have its cutting edge set exactly on the horizontal centerline of
the workpiece, not above center as with straight turning
Taper Attachment
The taper attachment (Figure 7-69 ) has many features of
special value, among which are the following:
The lathe centers remain in alignment and the center holes
in the work are not distorted.
The alignment of the lathe need not be disturbed, thus
saving considerable time and effort.
Taper boring can be accomplished as easily as taper
turning.
A much wider range is possible than by the offset method.
For example, to machine a 3/4-inch-per-foot taper on the
end of a bar 4 feet long would require an offset of 1 1/2
inches, which is beyond the capabilities of a regular lathe
but can be accomplished by use of the taper attachment.
Some engine lathes are equipped with a taper attachment as
standard equipment and most lathe manufacturers have a taper
attachment available. Taper turning with a taper attachment,
although generally limited to a taper of 3 inches per foot and
to a set length of 12 to 24 inches, affords the most accurate
means for turning or boring tapers. The taper can be set
directly on the taper attachment in inches per foot; on some
attachments, the taper can be set in degrees as well.
Ordinarily, when the lathe centers are in line, the work is
turned straight, because as the carriage feeds along, the tool is
always the same distance from the centerline. The purpose of
the taper attachment is to make it possible to keep the lathe
centers in line, but by freeing the cross slide and then guiding
it (and the tool bit) gradually away from the centerline, a taper
can be cut or, by guiding it gradually nearer the centerline
(Figure 7-70), a taper hole can be bored.