LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
or shoulder 1/4 inch high that is 6 inches from the small end. The shoulder
may be machined so that it forms a sharp corner with the small diameter, or
a fillet may be formed so that the corner is slightly rounded instead of
square.
(2) Mounting Workpiece For Shoulder Turning. The workpiece may be mounted
in a chuck or between centers for straight turning.
(3) Proper Cutter Bits For Shoulder Turning.
For turning the small
diameter portion of the workpiece down to the desired size, a roundnose
turning cutter bit is preferred. The shoulder is finished turned to size,
using a facing cutter bit if a square shoulder is required, or with a
roundnose turning cutter bit if a fillet is required. The roundnose cutter
bit may be specially ground to produce a special size fillet if necessary.
A parting cutter bit may be used at the shoulder location to mark the
position of the shoulder and, in some cases, to provide an undercut or
recess if a bearing is to be carried on the shoulder.
(4) Shoulder Turning Operation.
(a) The first important step in machining a circle is to locate the
shoulder correctly. Usually, the position is marked by bluing the workpiece
after it has been rough turned to the large diameter, accurately indicating
the shoulder location with the hermaphrodite calipers (figure 27 on page
63).
(b) The small diameter portion of the workpiece is then turned down by a
series of roughing cuts taken toward the shoulder. Take care to stop the
traverse of the cutter bit about 1/32 inch before it reaches the scribed
line; this 1/32 inch is important because it leaves sufficient metal on the
shoulder to provide for facing operation after the smaller diameter portion
has been turned to size.
(c) An alternate method of shoulder turning is to cut in at the shoulder
mark with a parting tool. If this is done, be sure that the bit does not
cut deeper than the required small diameter for square finished shoulders,
or deeper than the small diameter less the radius of the intended fillet if
a fillet is required. However, if the shoulder is to carry a bearing, it
may be desirable that an
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