Tc 9-524 fundamentals of machine tools

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TC 9-524
SPECIAL OPERATIONS ON THE LATHE
KNURLING ON THE LATHE
There are three pitches of rollers, coarse, medium, and tine
(Figure 7-9l).
Knurling is a process of impressing a diamond shaped or
straight line pattern into the surface of a workpiece by using
The diamond is the most common pattern and the medium
specially shaped hardened metal wheels to improve its
pitch is used most often. The coarse pitch is used for large-
appearance and to provide a better gripping surface. Straight
diameter work; the fine pitch is used for small-diameter
knurling is often used to increase the workpiece diameter
work.
when a press fit is required between two parts.
Knurling
Holding Devices for Knurling
The setup for knurling can be made between centers or
mounted in a solid chuck. Never attempt to knurl by holding
the work in a rubber or metal collet chuck, since the great
pressures of knurling could damage these devices. It is
important to support the work while knurling. If mounting
the work between centers, make the center holes as large as
possible to allow for the strongest hold. If using a chuck to
hold the work, use the tailstock center to support the end of
the work. If doing a long knurl, use a steady rest to support
the work and keep the piece from springing away from the
tool.
Knurling Tools
The knurling tool (Figure 7-10) can be designed differently,
but all accomplish the same operation. Two common types
of knurling tools are the knuckle joint and revolving head
type of knurling tools. The knuckle joint type is equipped
with a single pair of rollers that revolve with the work as it is
being knurled. The revolving head type of tool is fitted with
three pairs of rollers so that the pitch can be changed to a
different knurl without having to change the setup. There are
two knurl patterns, diamond and straight.
The knurling operation is started by determining the
location and length of the knurl, and then setting the machine
for knurling. A slow speed is needed with a medium feed.
Commonly, the speed is set to 60 to 80 RPM, while the feed
is best from 0.015 to 0.030 inch per revolution of the spindle.
The knurling tool must be set in the tool post with the axis of
the knurling head at center height and the face of the knurls
parallel with the work surface. Check that the rollers move
freely and are in good cutting condition; then oil the knurling
tool cutting wheels where they contact the workpiece. Bring
the cutting wheels (rollers) up to the surface of the work with
approximately 1/2 of the face of the roller in contact with the
work.
If the face of the roller is placed in this manner, the initial
pressure that is required to start the knurl will be lessened and
the knurl may cut smoother. Apply oil generously over the
area to be knurled. Start the lathe while forcing the knurls into
the work about 0.010 inch. As the impression starts to form,
engage the carriage feed lever (Figure 7-92). Observe the
knurl for a few revolutions and shut off the machine. Check to
see that the knurl is tracking properly, and that it is not on a
“double track” (Figure 7-93).