Varnishing The Caps

The caps are put into holes in counting plates, made of sheet brass, 15 inches by 12 inches, 0.5 inch thick, held in a frame of brass rods .35 inch square. This is quickly done by taking a parcel of caps on the plate, and shaking it sideways; the caps settle them-selves on the holes. When the plate is filled, the defective caps and those which have lost their charge are easily detected by the eye, and are replaced by perfect ones. The plate is placed on its bed in the varnishing machine, which is worked by hand, and each row of caps is brought in turn under a row of wires, which are alternately dipped into a pan of varnish, and then into the caps, leaving in each a drop of varnish.

The quantity of varnish placed in each cap can bo regulated by the size of the wires, or by the depth to which they enter the varnish. The caps remain in the plate thirty to forty minutes, when the varnish is sufficiently set to allow of their being turned into a tray for drying. These trays are of wood, 1 1/2 foot long, 1 foot wide, and 1 inch deep, and contain 2500 caps. The caps remain in the trays for three days, in a room heated to about 100°. They are then put into bags, and kept at the same temperature for ten days longer before they are packed in boxes.

One boy can count and varnish 7000 caps in an hour.

Materials required for 1,000,000 Caps.*

For The Caps

1300 pounds of sheet copper, of which about 1/3 is returned in scraps.

For The Powder

Mercury ... 42 lbs.

Nitric acid . • 330 "

Alcohol • • • 382 "

Nitre . . 21 "

For The Varnish

Gum shellac . . 10 lbs. Alcohol . . . 12 quarts.

For Bags. 31 yards of cotton duck, .75 yard wide.

For Boxes. 150 feet of white pine board.

Experience has shown that it is not safe to try to wash the percussion powder from partly filled caps. A lot of unvarnished caps, imperfectly filled, being soaked in water for several days, became coated with a substance much more explosive than the original fulminate. The percussion powder must be burned, and the cap polished by rolling in a dust barrel.

* Ordnance Manual, 186I.

Friction Primer For Cannons

The friction primer for cannons is a small brass tube filled with gunpowder, which is ignited by drawing a rough wire briskly through friction composition, contained in a smaller tube inserted into the first near the top, and soldered at right angle to it. A lanyard with a hook attached is used to ignite the primer.

The friction composition is made of -

Sulphuret of antimony . .. 2 parts. Chlorate of potash . . 1 part.

Moistened with gum water, 50 grains of gum Arabic in 2 ounces of water to 1 pound of composition.

The materials are first pulverized separately, mixed together dry, moistened with the gum water, and ground in an iron mill, such as is used for grinding paints.

The friction primer is composed of 1 large tube, 1 short tube, 1 wire rubber, friction composition, musket powder and wax.

The long tube is made from a circular disk of No. 19 sheet brass, 0.G2 inch in diameter, by means of a scries of five punches and dies, gradually diminishing in size to the last which is of the required size with the tube. The brass must be annealed before each punching.

The tube is cut to the prescribed length, measuring from the closed end by means of a circular saw, and the holes for the short tube and wire rubber are drilled, and the burrs removed. Length of the long tube 1.75 inch; exterior diameter 0.19 inch; interior diameter 1.75 inch; diameter of holes 0.15 inch, and 0.06 inch.

The short tube is formed from the long one by using two additional punches and dies, reducing the size each time. It is cut to the proper length by circular saws placed at the required distance apart, and the burr removed by rolling in a barrel. Length of the short tube 0.44 inch, exterior diameter 0.15 inch, interior diameter 0.133.

One end of the short tube is dipped into a solution of chloride of zinc, inserted in the hole drilled in the long tube, heated to redness in the flame of a spirit lamp, and soldered with soft solder; it is then washed and dried.

The wire rubber is made of No. 16 brass wire annealed, cut to the proper length, and pressed flat at one end by a machine for that purpose. The flat end is trimmed by a punch and die with dentated edges, and the tip is annealed in the flame of a spirit lamp. Length of wire 3.4 inches, length of flattened end 0.G5 inch.