ining of
aluminum and aluminum alloys is caused by the clogging of the chips,
especially when using such tools as counterbores and milling cutters.
This difficulty can be avoided largely by using the right kind of
cutting lubricant. Soap-water and kerosene are commonly employed. The
latter enables a fine finish to be obtained, provided the cutting tool
is properly ground.

The following information on this subject represents the experience of
the Brown-Lipe Gear Co., where aluminum parts are machined in large
quantities: For finishing bored holes, a bar equipped with cutters has
been found more practicable than reamers. The cutters used for machining
4-inch holes have a clearance of from 20 to 22 degrees and no rake or
slope on the front faces against which the chips bear. The roughing
cutters for this work have a rather sharp nose, being ground on the
point to a radius of about 3/32 inch, but for securing a smooth surface,
the finishing tools are rounded to a radius of about 3/4 inch. The
cutting speed, as well as the feed, for machining aluminum is from 50 to
60 per cent faster than the speeds and feeds for cast iron. The
lubricant used by this company is composed of one part "aqualine" and 20
parts water. This lubricant not only gives a smooth finish but preserves
a keen cutting edge and enables tools to be used much longer without
grinding. Formerly, a lubricant composed of one part of high-grade lard
oil and one part of kerosene was used. This mixture costs approximately
30 cents per gallon, whereas the aqualine and water mixture now being
used costs less than 4 cents per gallon, and has proved more effective
than the lubricant formerly employed.

CHAPTER II

LATHE TURNING TOOLS AND CUTTING SPEEDS

Notwithstanding the fact that a great variety of work can be done in the
lathe, the number of turning tools required is comparatively small. Fig.
1 shows the forms of tools that are used principally, and typical
examples of the application of these various tools are indicated in Fig.
2. The reference letters used in these two illustrations correspond for
tools of the same type, and both views should be referred to in
connection with the following description.

=Turning Tools for General Work.=--The tool shown at _A_ is the form
generally used for rough turning, that is for taking deep cuts when
considerable metal has to be removed. At _B_ a tool of the same type is
shown, having a bent end which enables it