Machinery Repairman

A knurling tool (fig. 6-16) forms a pattern on the
work by being fed into the work as it revolves. The
purpose of knurling is to give a roughened surface on
round metal parts, like knobs, to give a better grip for
handling. The knurled roller comes in a wide variety
of patterns. (See fig. 6-17.)
The boring bar toolholder is nothing more than a
piece of round stock with a screw-on cap (fig. 6-13).
The caps are available with square holes broached
through them at various angles and sizes. When the
proper size tool bit is inserted into the cap and the cap
is screwed on to the threaded end of the piece of round
stock, the entire unit becomes a very rigid boring tool,
which is used with the castle-type toolpost.
The quick-change toolholder, which is the most
widely used toolholder (fig. 6-18), is mounted on the
toolpost by sliding it from above and downward over
the dovetails. This toolholdcr has a height adjusting
ring to allow you to set the proper height before
locking it in place. The quick-change toolholder
comes in a wide range of styles. A few of these styles
are shown in figure 6-19.
LATHE CHUCKS
The lathe chuck is a device for holding lathe
work. It is mounted on the nose of the spindle. The
work is held by jaws that can be moved in radial slots
toward the center to clamp down on the sides of the
work. These jaws are moved in and out by screws
turned by a chuck wrench applied to the sockets
located at the outer ends of the slots.
Figure 6-19.—Quick-change toolholder.
The four-jaw independent lathe chuck, figure 6-20,
is the most practical for general work. The four jaws
are adjusted one at a time, making it possible to hold
work of various shapes and to adjust the center of the
work to coincide with the axial center of the spindle.
There are several different styles of jaws for
four-jaw chucks. You can remove some of the chuck
jaws by turning the adjusting screw and then
re-inserting them in the opposite direction. Some
chucks have two sets of jaws, one set being the
reverse of the other. Another style has jaws that are
bolted onto a slide by two socket-head bolts. On this
style you can reverse the jaws by removing the bolts,
reversing the jaws, and re-inserting the bolts. You can
make special jaws for this style chuck in the shop and
machine them to fit a particular size outside or inside
diameter.
28.302 28.304
Figure 6-18.—Quick-change toolpost and toolholder. Figure 6-20.—Four-jaw independent chuck.
6-13