The copper-base alloys used in this report are as follows; (a) yellow brass (Cu 60%, Zn 40%), (b) lead brass (Cu 58%, Zn 40%, Pb 2%), (c) tombasil (Cu 83%, Zn 13%, Si 4%). Length of hollow space in die is measured by a block gauge, while die-castings are measured by a measuring machine. Accordingly, the shrinkage is decided from the difference between these two dimensions. This experiment shows how the shrinkage is influenced by the casting temperature, the casting pressure, and the temperature of die. On the other hand, the blow hole and surface of die-castings are tested about the above specimens.

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It is well known that the vibration amplitudes of the balance wheel of a watch become about from 90° to 270°. This fact seems to be mainly due to the effect of the errors of the transmission system of the watch gears. The object of the present study is to make clear the transmission properties of the gear system of a watch, In this paper, however, we studied especially the torque transmission properties of the gear system, and the interference problem of the gear system will be studied in another occasion.
By the torque-meter designd by the writers shown in Fig. 1, we measured the magnitude of the pinion's torques transmitted through the other wheel. The experimental results show that there is a suitable center distance with maximum efficiency and minimum torque variation respectively for gear tooth of any size. The torque-var ation cannot be decreased below 20%, so far as the curve of circular arc is used for the form of gear tooth. The effect of the errors of wheel tooth form on the properties of the transmission efficiencies becomes larger than that of pinion tooth form. Generally these experimental results coincide with the theoretical results obtained by us.

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