ion (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 to the elbows, when they
are held in that position.

THE PROPER DIMENSIONS.--This plan will give you a sure means of
selecting a height that is best adapted for your work. The regulation
bench is about 38 inches high, and assuming that the vise projects up
about 4 inches more, would bring the top of the jaws about 42 to 44
inches from the floor. It is safe to fix the height of the bench at not
less than 34 inches.

This should have a drawer, preferably near the right-hand end of the
bench. The vise should be at the left side, and the bench in your front
should be free of any fixed tools.

HOW ARRANGED.--Have a rack above