| 摘要 |
PURPOSE:To easily manufacture a ball of a ball valve by advancing a drill from one side of a ball to form a round hole with a designated excess thickness portion left on the other side, and subsequently forming a fan-shaped opening on the excess thickness portion by a milling cutter. CONSTITUTION:In order to form a passing hole 8 having a circular opening 9 for the inflow of a fluid and a fan-shaped opening 10 for the outflow on a ball 3 of a ball valve, first a drill is advanced from the left of the ball 3 to the right to form a part of the passing hole 8 having the circular hole 9, with an excess thickness portion 3a left. Subsequently, a fan-shaped opening 10 is formed on the excess thickness portion 3a by a milling cutter. Thus, the ball 3 of the ball valve can be formed only by cutting, so that manufacturing work can be facilitated considerably.
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