Practical Mechanics for Boys | Page 9

it that the drills are in good shape;
and while you are about it, look over the lathe tools. You will find that
it is better to do this work at one time, than to go to the emery wheel a
dozen times a day while you are engaged on the job.
Adopt a system in your work. Don't take things just as they come along,
but form your plans in an orderly way, and you will always know how
to take up and finish the work in the most profitable and satisfactory
way.
WRONG USE OF TOOLS.--Never use the vise as an anvil. Ordinary
and proper use of this tool will insure it for a lifetime, aside from its
natural wear. It may be said with safety that a vise will never break if
used for the purpose for which it was intended. One blow of a hammer
may ruin it.
Furthermore, never use an auxiliary lever to screw up the jaws. If the
lever which comes with it is not large enough to set the jaws, you may
be sure that the vise is not large enough for your work.
CHAPTER III
SETTING AND HOLDING TOOLS
Some simple directions in the holding and setting of tools may be of
service to the novice. Practice has shown the most effective way of
treating different materials, so that the tools will do the most efficient
work.
A tool ground in a certain way and set at a particular angle might do the
work admirably on a piece of steel, but would not possibly work on
aluminum or brass.
LATHE SPEED.--If the lathe should run at the same speed on a piece
of cast iron as with a brass casting, the result would not be very
satisfactory, either with the tool or on the work itself.

Some compositions of metal require a high speed, and some a hooked
tool. These are things which each must determine as the articles come
to the shop; but there are certain well-defined rules with respect to the
ordinary metals that should be observed.
THE HACK SAW.--Our first observation should be directed to the
hand tools. The hack saw is one of the most difficult tools for the
machinist to handle, for the following reasons:
First, of the desire to force the blade through the work. The blade is a
frail instrument, and when too great a pressure is exerted it bends, and
as a result a breakage follows. To enable it to do the work properly, it
must be made of the hardest steel. It is, in consequence, easily
fractured.
[Illustration: Fig. 28.--Hack Saw Frame.]
[Illustration: Fig. 29.--Hack Saw Blade.]
Second. The novice will make short hacking cuts. This causes the teeth
to stick, the saw bends, and a new blade is required. Take a long
sweeping cut, using the entire length of the blade. Do not oscillate the
blade as you push it through the work, but keep the tooth line
horizontal from one end of the stroke to the other. The moment it
begins to waver, the teeth will catch on the metal on the side nearest to
you, and it will snap.
Third. The handle is held too loosely. The handle must be firmly held
with the right hand, and the other held by the fingers lightly, but in such
a position that a steady downward pressure can be maintained. If
loosely held, the saw is bound to sag from side to side during the stroke,
and a short stroke accentuates the lateral movement. A long stroke
avoids this.
The hack saw is one of the tools which should be used with the utmost
deliberation, combined with a rigid grasp of the handle.
FILES.--For remarks on this tool see Chapter IV, which treats of the

subject specially.
GRINDSTONES, EMERY AND GRINDING WHEELS.--A good
workman is always reflected by his grinding apparatus. This is true
whether it has reference to a grindstone, emery, corundum wheel, or a
plain oil stone. Nothing is more destructive of good tools than a
grooved, uneven, or wabbly stone. It is only little less than a crime for a
workman to hold a tool on a revolving stone at one spot.
CARELESSNESS IN HOLDING TOOLS.--The boy must learn that
such a habit actually prevents the proper grinding, not only of the tool
he has on the stone, but also of the one which follows. While it is true
that all artificially made grinders will wear unevenly, even when used
with the utmost care, due to uneven texture of the materials in the stone,
still, the careless use of the tool, while in the act of grinding, only
aggravates the trouble.
Another fault of the careless workman is, to press the bit against the
stone too hard. This cuts the stone