centrifugal casting methods were adopted for manufacturin

After the mold had been heated, the prepared  molten  metal was poured into the sprue and the  bell  swung first in pendulum style, then in a  circular  motion, to force the metal into all areas  of  the pattern chamber. This action re‐sembled  the  old trick of swinging a bucketful of water  over  one's head in a circular motion. After 1920,  the  process began to be used for the  manufac ‐turing of cast iron water pressure pipe,  and  use of the process has been ex‐tended to a  much  wider range of shapes and alloys.

In 1940, centrifugal casting methods were adopted for  manufacturing  jewelry and soon they became available  to  the nonprofessionai craftsman. Prior to its use in the  jewelry  trade, vacuum action was combined with the  investing  procedures of mold making to produce an air free  mold which was patented in 1935. Vacuum casting,  combined  with centrifugal casting was also attempted in  1935,  and patents on this method were finally issued in  1940 ‐42. However, successful vacuum‐centrifugal casting  was  not ac‐complished until 1948 by A.L. Englehardt.  Continuous  improvements in all the various machines,  including  large production models employing this  centrifugal  casting method, continued to make this form  of  casting ex‐tremely popular and versatile for both the  professional  and the novice craftsman.

• In centrifugal casting, the mold may spin about a  horizontal,  inclined or vertical axis. The outside shape of  the  casting is determined by the shape of the mold. The  inside  contour is determined by the free surface of the  liquid  metal during solidification. The centrifugal force  produced  by rotation is large compared with normal  hydrostatic  forces and is utilized in two ways.