Page:Popular Science Monthly Volume 90.djvu/973

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Popular Science Monthly

��957

��not to melt the aluminum. They should then be stamped between a flat piece of marble, such as a table top, wash bowl top, etc., and a hard flat surface 3 or 4 in. square. A blow of from 10 to 15 lb. with an ordinary hammer is sufficient. Two pieces of marble were used by the author to straighten the disks, with excellent results. The large aluminum plates do not need to be straightened unless badly warped.

.The small piece of fiber, included in the list of parts, can now be sawed into two i-in. squares, and these drilled through the exact center with the 17/64-in. drill, and then bolted to the 3-in. brass disks, both pieces on one side, so that four J/g-in- holes can be drilled in the fiber to correspond with those in the brass plates near the center. When this is done these four small holes in the brass disks should be counter- sunk with the 17/64-in. drill, on one side of each disk.

In the exact center of the bottom of the round pasteboard box, mentioned under "materials," a 17/64-in. hole should be urilled, and one of the large brass machine screws inserted from the outside of the box. An extra heavy pasteboard washer 2^ in. in diameter with a 17/64-in. hole in the center, should next be slipped over the machine screw and pushed to the bottom of the box, inside. This washer should be about K-in. thick. It should be followed by two or three of the thin cardboard washers which were not sawed out in the center.

One of the brass disks can now be slid down on the brass bolt, the side on which the holes were countersunk facing up. Wire nails with their heads removed should next be placed in each of the four counter- sunk holes, points up; also two opposite holes near the circumference should have nails so inserted in them.

By placing the various disks and washers over the machine screw, and using the nails in the 3^-in. holes as guides, a pile of parts should be built up in the following order: I brass disk, 2 cardboard washers, i small aluminum disk, i cardboard washer, i large aluminum disk, i cardboard washer, I small aluminum disk, etc., ending with the other brass disk, placed countersunk side in, and preceded by 2 washers of cardboard, as at E.

The four center nails should now be removed, care being taken not to disturb the pile of parts, and the few remaining cardboard washers, with the small center

��holes, placed on the machine screw, and held down tight while a nut is put on the machine screw, and turned down as hard as possible by hand, and one complete turn with pincers. Too much pressure should be avoided, as it is only desired that the parts should be held in place so as to lie flat against each other, without reducing the thickness of the cardboard through

���The mold of wood which is clamped in place for running molten lead over the movable plates

compression. A quarter sectional view ©f a completed pile is shown at E.

If all the steps indicated have been properly followed out, there should be a fairly uniform annular space between the pile of disks and the wall of the box. Into this space sufficient melted lead should be poured to cover the complete pile of disks to the top edge of the last piece of card- board after the 2 nails near the edges of the disks have been removed. The molten metal should be heated in two small pans or ladles for a short time after melting, and all scum and dirt removed from the top. When this has been done two streams of melted lead can be poured in simul- taneously, from opposite points near the edge of the round box.

The lead should be run as quickly as possible without spattering. It must be kept going till the necessary amount has been poured.

As soon as the lead has cooled the machine screw can be taken out and the complete casting removed from the box. When this has been done the stray pieces of lead can be cut from the top of the pile, so that the cardboard can be removed from the top as well as from the bottom.

The four nails which were removed from the small center holes should now be re- inserted and melted paraffin should be poured into the 17/64-in. hole in the center

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