idea of accuracy to be rated as a first-class mechanic. Ordinary
compasses are obstinate when we try to set them to the hundredth of an
inch; usually the points are dull and ill-shapen; if they make a
puncture in the paper it is unsightly.

Watchmakers have one advantage, however, because they can very easily
work over a cheap set of drawing instruments and make them even superior
to anything they can buy at the art stores. To illustrate, let us take a
cheap pair of brass or German-silver five-inch dividers and make them
over into needle points and "spring set." To do this the points are cut
off at the line _a a_, Fig 11, and a steel tube is gold-soldered on each
leg. The steel tube is made by taking a piece of steel wire which will
fit a No. 16 chuck of a Whitcomb lathe, and drilling a hole in the end
about one-fourth of an inch deep and about the size of a No. 3 sewing
needle. We Show at Fig. 12 a view of the point _A'_, Fig. 11, enlarged,
and the steel tube we have just drilled out attached at _C_. About the
best way to attach _C_ is to solder. After the tube _C_ is attached a
hole is drilled through _A'_ at _d_, and the thumb-screw _d_ inserted.
This thumb-screw should be of steel, and hardened and tempered. The use
of this screw is to clamp the needle point. With such a device as the
tube _C_ and set-screw _d_, a No. 3 needle is used for a point; but for
drawings on paper a turned point, as shown at Fig 13, is to be
preferred. Such points can be made from a No. 3 needle after softening
enough to be turned so as to form the point _c_. This point at the
shoulder _f_ should be about 12/1000 of an inch, or the size of a
fourth-wheel pivot to an eighteen size movement.

[Illustration: Fig. 11]

[Illustration: Fig. 12]