l could not possibly work, except to act as a
scraper, and if it should be used in that position on cast iron, the
tool itself would soon be useless.

[Illustration: _Fig. 36. Correct Angle_ _Fig. 37. Wrong Angle_]

Fig. 39 is still worse, and is of no value for any purpose except in
polishing brass, where it would be serviceable. It would make a sorry
looking job with aluminum. Brass requires a tool with very little top
rake, and the point should be set near the center line C.

LATHE SPEED.--It is often a question at what speeds to run the lathe for
different work. If you know the speeds of your lathe at low and high
gear, you must also consider the diameter of the work at the cutting
point.

The rule is to have the bit cut from 15 to 20 feet per minute for
wrought iron; from 11 to 18 feet for steel; from 25 to 50 for brass; and
from 40 to 50 for aluminum.

[Illustration: _Fig. 38. Too Low_ _Fig. 39. Improper Set_]

As a result, therefore, if, at low speed, a piece 10 inches in diameter,
runs at the proper speed to cut at that distance from the center, it is
obvious that a piece 5 inches in diameter should ran twice as fast. This
is a matter which time and practice will enable you to judge with a fair
degree of accuracy.

Observe this as a maxim: "Slow speed, and quick feed."

BORING TOOLS ON LATHE.--The lathe is a most useful tool for boring
purposes, better for some work than the drilling machine itself. The
work which can be done better on a lathe than on a drilling machine, may
be classified as follows:

1. When straight and true holes are required.

2. In long work, where the lathe is used to turn up the article, and
where the drilling can be done at the same time.

3. Anything that can be chucked in a lathe.

4. Where the work is long and cannot be fixed in a drilling machine. The
long bed of the lathe gives room for holding such work.

[Illustration: _Fig. 40. Internal Set_ _Fig. 41. Set for Brass_]

THE RAKE OF THE DRILL.--A boring tool requires some knowledge in
setting. It should have a greater top rake than for the outside work,
and the cutting edge should also be keener, as a rule.

[Illustration: _Fig. 42.--Surface Gage._]

In this class of work the material bored must be understood, as well as
in doing outside work.

The hooked tool, Fig. 40, is shown to be considerably above the center
line, and at that point it will do the most effective cutting on steel.
If, on the other hand, bras