After piece A is finished, it is removed from B and B is reversed in
the lathe so that the boss may be knurled.
In case there is enough room between the dog and the work, when held as
in Fig. 30, there is no need to reverse the work for knurling since it
can be done in this position.
The boss at the end of B is used as a handle so that if it were left
smooth it would be hard to turn by hand. The surface is therefore made
rough with a knurling tool as shown in Fig. 32.
[Illustration: Fig. 32]
The speed of the lathe should be about the same for knurling as for
thread cutting. If the lathe runs too fast, the knurling tool does not
cut satisfactorily.
The tool is set so that the face of the rollers is parallel with the
surface to be knurled. When starting the cut, the rollers can be forced
into the piece easier if about half of their width extends past the end
of the work.
The knurling tool should be pressed into the work fast enough so that
about one half the depth of the finished knurl will be cut while the
lathe makes three or four revolutions. If the tool is forced in too
slow, it will cut a finer knurled surface than the rollers are intended
to cut.
The tool is fed along the surface in the same manner as in plain
turning. The speed at which the carriage of the lathe moves has no
effect upon the pitch of the knurled surface since this is controlled
by the pitch of the grooves in the rollers. If a finer knurled surface
is desired, a knurling tool having rollers with finer grooves would
have to be used.