osition _x_, Fig.
5, it is returned to the starting point and the work is reversed in the
centers, the dog being placed upon the other end. The unfinished part is
then turned, and if the cross-slide is not moved, the tool will meet the
first cut. It is not likely that the two cuts will be joined or blended
together perfectly, however, and for this reason a cut should be
continuous when this is possible.

=Roughing and Finishing Cuts.=--Ordinarily in lathe work, as well as in
other machine work, there are two classes of cuts, known as "roughing"
and "finishing" cuts. Roughing cuts are for reducing the work as
quickly as possible almost to the required size, whereas finishing cuts,
as the name implies, are intended to leave the part smooth and of the
proper size. When the rough stock is only a little larger than the
finished diameter, a single cut is sufficient, but if there is
considerable metal to turn away, one or more deep roughing cuts would
have to be taken, and, finally, a light cut for finishing. In this
particular case, one roughing and one finishing cut would doubtless be
taken, as the diameter has to be reduced 3/8 inch. Ordinarily the
roughing cut would be deep enough to leave the work about 1/32 or
perhaps 1/16 inch above the finished size. When there is considerable
metal to remove and a number of roughing cuts have to be taken, the
depth of each cut and the feed of the tool are governed largely by the
pulling power of the lathe and the strength of the work to withstand the
strain of a heavy cut. The depth of roughing cuts often has to be
reduced considerably because the part being turned is so flexible that a
heavy cut would spring the work and cause the tool to gouge in. Of
course, just as few cuts as possible should be taken in order to save
time. The speed of the work should also be as fast as the conditions
will allow for the same reason, but as there are many things which
govern the speed, the feed of the tool, and the depth of the cut, these
important points are referred to separately in Chapter II.

=Filing and Finishing.=--In many cases the last or finishing cut does
not leave as smooth a surface as is required and it is necessary to
resort to other means. The method commonly employed for finishing in the
lathe is by the use of a file and emery cloth. The work is rotated
considerably faster for filing than for turning, and the entire surface
is filed by a flat, single-cut file, held as shown in Fig