To fully appreciate such a large escapement model as we have been describing, a person must see it with its great balance, nearly 4” across, flashing and sparkling in the show window in the evening, and the brilliant imitation ruby pallets dipping in and out of the escape wheel.  A model of this kind is far more attractive than if the entire train were shown, the mystery of “What makes it go?” being one of the attractions.  Such a model is, further, of great value in explaining to a customer what you mean when you say the escapement of his watch is out of order.  Any practical workman can easily make an even $100 extra in a year by making use of such a model.

For explaining to customers an extra balance cock can be used to show how the jewels (hole and cap) are arranged.  Where the parts are as large as they are in the model, the customer can see and understand for himself what is necessary to be done.

It is not to be understood that our advice to purchase the jewels for an extra balance cock conflicts with our recommending the reader not to jewel the holes of his model.  The extra cock is to be shown, not for use, and is employed solely for explaining to a customer what is required when a pivot or jewel is found to be broken.

HOW LARGE SCREWS ARE MADE.

The screws which hold the plates in place should have heads about 3/8” in diameter, to be in proportion to the scale on which the balance and escape wheel are gotten up.  There is much in the manner in which the screw heads are finished as regards the elegance of such a model.  A perfectly flat head, no matter how highly polished, does not look well, neither does a flattened conehead, like Fig. 35.  The best head for this purpose is a cupped head with chamfered edges, as shown at Fig. 34 in vertical section.  The center b is ground and polished into a perfect concave by means of a metal ball.  The face, between the lines a a, is polished dead flat, and the chamfered edge a c finished a trifle convex.  The flat surface at a is bright, but the concave b and chamfer at c are beautifully blued.  For a gilt-edged, double extra head, the chamfer at c can be “snailed,” that is, ground with a suitable lap before bluing, like the stem-wind wheels on some watches.

[Illustration:  Fig. 34]

[Illustration:  Fig. 35]

FANCY SCREWHEADS.

There are two easy methods of removing the blue from the flat part of the screwhead at a. (1) Make a special holder for the screw in the end of a cement brass, as shown at E, Fig. 36, and while it is slowly revolving in the lathe touch the flat surface a with a sharpened pegwood wet with muriatic acid, which dissolves the blue coating of oxide of iron. (2) The surface of the screwhead is coated with a very thin coating of shellac dissolved in alcohol