with a cutting lubricant is an objectionable feature
which, in the opinion of many, more than offsets the increase in cutting
speed that might be obtained.

Turret lathes and automatic turning machines are equipped with a pump
and piping for supplying cooling lubricant to the tools in a continuous
stream. Engine lathes used for general work, however, are rarely
provided with such equipment and a lubricant, when used, is often
supplied by a can mounted at the rear of the carriage, having a spout
which extends above the tool. Owing to the inconvenience in using a
lubricant on an engine lathe, steel, as well as cast iron, is often
turned dry especially when the work is small and the cuts light and
comparatively short.

=Lubricants Used for Turning.=--A good grade of lard oil is an excellent
lubricant for use when turning steel or wrought iron and it is
extensively used on automatic screw machines, especially those which
operate on comparatively small work. For some classes of work,
especially when high-cutting speeds are used, lard oil is not as
satisfactory as soda water or some of the commercial lubricants, because
the oil is more sluggish and does not penetrate to the cutting point
with sufficient rapidity. Many lubricants which are cheaper than oil are
extensively used on "automatics" for general machining operations. These
usually consist of a mixture of sal-soda (carbonate of soda) and water,
to which is added some ingredient such as lard oil or soft soap to
thicken or give body to the lubricant.

A cheap lubricant for turning, milling, etc., and one that has been
extensively used, is made in the following proportions: 1 pound of
sal-soda, 1 quart of lard oil, 1 quart of soft soap, and enough water to
make 10 or 12 gallons. This mixture is boiled for one-half hour,
preferably by passing a steam coil through it. If the solution should
have an objectionable odor, this can be eliminated by adding 2 pounds of
unslaked lime. The soap and soda in this solution improve the
lubricating quality and also prevent the surfaces from rusting. For
turning and threading operations, plain milling, deep-hole drilling,
etc., a mixture of equal parts of lard oil and paraffin oil will be
found very satisfactory, the paraffin being added to lessen the expense.

Brass or bronze is usually machined dry, although lard oil is sometimes
used for automatic screw machine work. Babbitt metal is also worked dry,
ordinarily, although kerosene o