Method of measuring hardness of flexible thread-wound golf balls or inner cores thereof

摘要

A method of measuring hardness of a flexible thread-wound golf ball or its inner core which includes the steps of holding the flexible thread-wound golf ball or its inner core to be measured between a transmitter coupled to an ultrasonic wave oscillating source and a receiver coupled to an ultrasonic wave detecting device which detects the ultrasonic wave received by said receiver, applying from the transmitter, the ultrasonic wave having predetermined frequency to the flexible thread-wound golf ball or its inner core, and measuring the hardness of the flexible thread-wound golf ball or its inner core selectively by or based on the propagation time of the ultrasonic wave passing through the central portion of the flexible thread-wound golf ball or its inner core.