Abstract: A new method for automatically detecting the large screw thread is discussed by using the neotype gauge head of thread which includes TESA inductance type transducer and survey probe chosen according to the tooth-type of thread. The way of contact measurement is adopted on the basis of the synthetically measuring principle for thread. The functional diameter of thread is investigated and analyzed experimentally. Through spectrum analysis, the dynamic error is picked out while data of functional diameter of thread will be obtained. Because the measurement strength of the neotype gauge head is much smaller than that of the regular screw gauge so as to diminish the most measurement error resulted from the contact stress. Experimental results show that the neotype gauge head of thread can improve measuring accuracy and the measuring accuracy reaches 1µm after data processing.

Key words: Functional diameter of thread, Large screw thread, Neotype gauge head of thread, Online test