uts
_N_. Bar _E_ is also clamped to the toolslide by bolt _H_, as previously
stated. The attachment is disconnected for straight turning by simply
loosening clamp _C_ and the bolt _H_.

=Application of Taper Attachment.=--Practical examples of lathe work,
which illustrate the use of the taper attachment, are shown in Figs, 11
and 12. Fig. 11 shows how a taper hole is bored in an engine
piston-head, preparatory to reaming. The casting must be held either in
a chuck _C_ or on a faceplate if too large for the chuck. The side of
the casting (after it has been "chucked") should run true, and also the
circumference, unless the cored hole for the rod is considerably out of
center, in which case the work should be shifted to divide the error.
The side of the casting for a short space around the hole is faced true
with a round nose turning tool, after which the rough-cored hole is
bored with an ordinary boring tool _t_, and then it is finished with a
reamer to exactly the right size and taper.

This particular taper attachment is set to whatever taper is given on
the drawing, by loosening nuts _N_ and turning slide _S_ until pointer
_P_ is opposite that division on the scale which represents the taper.
The attachment is then ready, after bolt _H_ and nuts _N_ are tightened,
and clamp _C_ is fastened to the lathe bed. The hole is bored just as
though it were straight, and as the carriage advances, the tool is
gradually moved inward by the attachment. If the lathe did not have a
taper attachment, the taper hole could be bored by using the compound
rest.

[Illustration: Fig. 11. Lathe with Taper Attachment arranged for Boring
Taper Hole in Engine Piston]

The hole should be bored slightly less than the finish size to allow for
reaming. When a reamer is used in the lathe, the outer end is supported
by the tailstock center and should have a deep center-hole. The lathe is
run very slowly for reaming and the reamer is fed into the work by
feeding out the tailstock spindle. The reamer can be kept from
revolving, either by attaching a heavy dog to the end or, if the end is
squared, by the use of a wrench long enough to rest against the lathe
carriage. A common method is to clamp a dog to the reamer shank, and
then place the tool-rest beneath it to prevent rotation. If the shank
of a tool is clamped to the toolpost so that the dog rests against it,
the reamer will be prevented from slipping off the center as it tends to
do; with this