Diameter measuring device

An apparatus for measuring the diameter of an object having a continuously indexable surface, the object being located with respect to a fixed surface and rotatable about an axis, comprising:

• fixture means attached to the fixed surface;
• wheel means of known diameter rotatably attached to said fixture means, the rotational axis of said wheel means being substantially parallel to the rotational axis of the object to be measured;
• said wheel means being adapted to contact the surface of the object to be measured and be movable in a direction parallel to the object rotational axis during object diameter measurement;
• encoder means attached to said wheel means for producing a signal indicative of rotation of said wheel means;
• start and end means for determining at least one revolution of the object about its rotational axis and for producing signals indicative of the start and end of a revolution and indicative of the number of revolutions completed;
• means responsive to said encoder means and said start and end means for determining the rotational travel of said wheel means between the start and end of at least one revolution of the object and producing a signal indicative thereof;
• means for calculating the diameter of the object responsive to said rotational travel determination means, said start and end means, and the diameter of said wheel means and for producing a signal indicative thereof;
• and
• means responsive to said calculation means for displaying the calculated diameter of the object.