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Show MAKE SOLID GOLD CASTINGS Dentists Have Clever Method of Securing Se-curing Piece of Metal Which Is Free from All Blowholes. (By ALBERT F. BISHOP, In the Scientific Scien-tific American.) Dentists have a very clever method of making solid gold castings. A train of gears is employed, which revolves a spindle that carries two- Jointed arms. The outer end of one arm has an inclosure where the little mold Is placed, while the other arm carries a counterbalance. Just in front of the mold is a fireclay block, hollowed to receive the gold which is melted with the blowpipe. The gearing is rapidly worked by hand, revolving the melted gold, which is forced very quickly into the mold. Owing to centrifugal force, a very solid and clean-cut casting is made, which is free from blowholes. Casting Gold Centrifugally. J In making the mold, it is necessary for the dentist first to make a pattern. pat-tern. This is done by tilling the cavity cav-ity in the tooth with wax. A wire attached at-tached to the pattern holds it in place while the clay mold is being made, as shown in one of the figures. When the mold is complete, the wax is melted melt-ed out. Another figure shows a section sec-tion of the mold as when placed on a rotary arm, also the block in which the gold is melted. j .f : |