Practical Mechanics for Boys | Page 6

time to time.
Everything in the machine shop centers about the lathe. It is the king of
all tools. The shaper and planer may be most efficient for surfacing,
and the milling machine for making grooves and gears, or for general
cutting purposes, but the lathe possesses a range of work not possible
with either of the other tools, and for that reason should be selected
with great care.
[Illustration: Fig. 9. Handy Bench Vise.]
SELECTING A LATHE.--The important things about a lathe are the
spindle bearings and the ways for the tool-holder. The least play in
either will ruin any work. Every other part may be defective, but with
solidly built bearing-posts and bearings, your lathe will be effective.
For this reason it will not pay to get a cheap tool. Better get a small,
6-inch approved tool of this kind, than a larger cheap article. It may pay
with other tools, but with a lathe never.
Never do grinding on a lathe. The fine emery, or grinding material, is
sure to reach the bearings; it matters not what care is exercised. There
is only one remedy for this--overhauling.
[Illustration: Fig. 10.--Combination Square.]
COMBINATION SQUARE.--A tool of this kind is most essential,
however small. It can be used as a try-square, and has this advantage,

that the head can be made to slide along the rule and be clamped at any
point. It has a beveling and a leveling device, as well.
[Illustration: Fig. 11.--Uses of the Combination Square.]
The combination square provides a means for doing a great variety of
work, as it combines the qualities of a rule, square, miter, depth gage,
height gage, level and center head.
[Illustration: Fig. 12.--A Quick Adjusting Micrometer.]
The full page illustration (Fig. 11) shows some of the uses and the
particular manner of holding the tool.
MICROMETERS.--Tools of this description are made which will
accurately measure work in dimensions of ten-thousandths of an inch
up to an inch.
The illustration (Fig. 12) shows an approved tool, and this is so
constructed that it can instantly be changed and set by merely pressing
the end of the plunger as shown.
[Illustration: Fig. 13.--A Universal Bevel Protractor.]
PROTRACTORS.--As all angles are not obtainable by the square or
bevel, a protractor is a most desirable addition to the stock of tools. As
one side of the tool is flat it is convenient for laying on the paper when
drafting, as well as for use on the work.
The protractor has a graduated disk, and is adjustable so it can be
disposed at any angle.
[Illustration: Fig. 14.--Universal Bevel Protractor, showing its uses.]
All special tools of this kind are serviceable, and the boy should
understand their uses, even though he is not able for the time being to
acquire them. To learn how they are applied in daily use is an education
in itself.

UTILIZING BEVEL PROTRACTOR.--Examine the full-page
illustration (Fig. 14), and see how the bevel protractor is utilized to
measure the angles of work, whether it is tapering heads or different
kinds of nuts, or end and side surfacing, and it will teach an important
lesson.
[Illustration: Fig. 15.--Grindstone Truing Device.]
TRUING GRINDSTONES.--Devices for truing up grindstones are now
made, and the illustration (Fig. 15) shows a very efficient machine for
this purpose. It can be applied instantly to the face of the stone, and it
works automatically, without interfering with the use of the stone.
It is frequently the case that an emery wheel will become glazed, due to
its extreme hardness. This is also caused, sometimes, by running it at
too high a speed. If the glazing continues after the speed is reduced, it
should be ground down an eighth of an inch or so. This will, usually,
remedy the defect.
[Illustration: Fig. 16.--Set of Tools and Case.]
SETS OF TOOLS.--A cheap and convenient set of precision tools is
shown in Fig. 16, which is kept in a neat folding leather case. The set
consists of a 6-inch combination square, complete center punch, 6-inch
flexible steel rule center gage, 4-inch calipers, 4-inch outside caliper
with solid nut, 4-inch inside caliper with solid nut, and a 4-inch divider
with a solid nut.
[Illustration: Fig. 17. The Work Bench.]
THE WORK BENCH.--This is the mechanic's fort. His capacity for
work will depend on its arrangement. To the boy this is particularly
interesting, and for his uses it should be made full three inches lower
than the standard height.
A good plan to judge of the proper height is to measure from the jaws
of the vise. The top of the jaw should be on a level with the elbows.
Grasp a file with both hands, and hold it as though in the act of filing

across the work; then measure up from the floor