Thread gauge

Claim 1

In a thread gauging device for measuring the pitch diameter of helical threads and for self-alignment with the pitch of said threads: (a) a caliper including (i) a frame, (ii) a fixed blade element extending from said frame, (iii) a movable blade element carried by said frame and parallel to said fixed blade element and movable relative thereto while maintaining said parallel relation, and (iv) a scale for indicating the degree of separation between said blade elements; (b) a pair of thread gauge attachments carried by one of said blade elements in longitudinally spaced relation along that blade element; (c) a single thread gauge attachment carried by the other of said blade elements substantially at the middle of a longitudinal extent corresponding to the spacing of said thread gauges attached to the other of said blade elements; (d) a base element included in each thread gauge attachment and in sliding engagement with the blade element associated therewith; (e) each of said base elements being formed with a groove which slidably receives one of said blade elements; (f) spring means on each of said base elements cooperating with the blade on which that base element is mounted to maintain that base element in sliding relation to the blade element; and (g) a contact member carried by each of said base elements and receivable in thread grooves; (h) said base elements being reversably positionable on said blade elements such that a pair said contacts on one blade element and one of said contacts on the other blade element may alternatively face toward or away from each, the contact members of the pair of base elements on one thread gauge attachment being engaged with thread grooves in spaced relation with respect to the contact member in the other of said thread gauge attachments which is received in a thread groove between the thread grooves engaged by the pair of contact members on the other of said thread gauge attachments.