| 摘要 |
A device for determining the placement of gripping holes with respect to the pin and/or the center of gravity and/or the mass bias of a bowling ball has a meridian plane indicator, a vertical axis plane indicator and a horizontal axis plane indicator. The meridian plane indicator has a scale which determines the distance between placements of finger holes and a thumb hole for bowling balls. The vertical axis plane indicator has a scale which determines the distance from the horizontal axis plane to the location of the positive axis point. The horizontal axis plane indicator has two scales; the first determines the distance between the meridian plane and the vertical axis plane about the surface of the ball along the horizontal axis plane, the second scale determines the angular displacement of the meridian plane and the vertical axis plane. The vertical axis plane indicator is pivotally connected to the meridian plane indicator and has a means of temporarily affixing its position to the horizontal plane indicator. This allows the device to use cooperating scales to directly read the axis coordinates from a previously drilled ball, or to pre-set the device to a particular bowler's axis coordinates to speed up the process of marking a new ball in preparation for drilling. The device also has an adaptation to permit the drawing of various size arcs on the bowling ball surface to quickly and accurately locate the desired positive axis point.
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