Perhaps we cannot do our readers a greater favor than to digress from the study of the detached lever escapement long enough to say a few words about drawing instruments and tablets or surfaces on which to delineate, with due precision, mechanical designs or drawings.  Ordinary drawing instruments, even of the higher grades, and costing a good deal of money, are far from being satisfactory to a man who has the proper 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]

[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.