Fig. 137.—A Tumbling Barrel.
Fig. 138.—Another Form.
The Tumbling Barrel Process.
This process of japanning small castings is very successful in those cases where the parts are small and intricate in construction, and, therefore, cannot either be dipped or sprayed, excepting with some difficulty. The great advantage of tumbling is that such work is done better and faster than by dipping. A machine, of which two examples are shown in Figs. 137 and 138, is used in this process. Inside this machine are placed a number of shot or steel balls of different sizes. The articles to be treated are then introduced in the japan and the machine is started at varying degrees of speed. The shot carries the japan over the various parts and into the interstices. As different objects and materials require different speeds, some work will be started slowly and the speed increased to get the desired finish. The objects are then dumped out on to wire screens or baskets, and shaken, when the steel balls and shot fall through the mesh, leaving the articles that have been japanned behind. The baskets are then hung in baking ovens, while the balls are washed in gasoline ready for use. The machines mentioned above are manufactured by the Baird Machine Co., Bridgeport, Connecticut, U.S.A. The English agents are R. Cruickshank, Ltd., Camden Street, Birmingham.