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]

[Illustration: Fig. 13]

[Illustration: Fig. 14]

The idea is, when drawing on paper the point _c_ enters the paper. For
drawing on metal the form of the point is changed to a simple cone, as
shown at _B'_ _c_, Fig. 13. such cones can be turned carefully, then
hardened and tempered to a straw color; and when they become dull, can
be ground by placing the points in a wire chuck and dressing them up
with an emery buff or an Arkansas slip. The opposite leg of the dividers
is the one to which is attached the spring for close setting of the
points.

In making this spring, we take a piece of steel about two and
one-fourth inches long and of the same width as the leg of the divider,
and attach it to the inside of the leg as shown at Fig. 14, where _D_
represents the spring and _A_ the leg of the dividers. The spring _D_
has a short steel tube _C''_ and set-screw _d''_ for a fine point like
_B_ or _B'_. In the lower end of the leg _A_, Fig. 14, is placed the
milled-head screw _g_, which serves to adjust the two points of the
dividers to very close distances. The spring _D_ is, of course, set so
it would press close to the leg _A_ if the screw _g_ did not force it
away.

SPRING AND ADJUSTING SCREW FOR DRAWING INSTRUMENTS.

[Illustration: Fig. 15]

It will be seen that we can apply a spring _D_ and adjusting screw
opposite to the leg which carries the pen or pencil point of all our
dividers if we choose to do so; but it is for metal drawing that such