Inspecting tapped holes

Inspecting tapped holes

Keyword: Inspection

Verifying the quality of blind tapped holes is difficult in many high-volume manufacturing industries. Broken taps, wrong thread sizes, and incorrectly located holes cause production stoppages and damaged equipment in assembly operations. Manual inspections are labour intensive and subject to human error. On the other hand, designing an automated approach capable of identifying all types of bad holes has proved elusive.

A simple motorised probe that is equipped with a torque monitor may find broken taps or missing holes, but is not as useful for finding oversize or undersize threads, said Al Peplinski, president of Eagle Thread Verifier Inc. in Sterling Heights, Michigan. "The missing element was a control system intelligent enough to make sense out of the full range of possible probe feedback", he added.

Eagle's answer is a patented thread verification system that can quickly monitor thread depth, size and location, and can identify untapped holes, broken taps, and incorrect pitch diameters. The system uses a motor-driven test plug rotating within the tapped hole. A torque monitor on the motor generates feedback to the control system, which is provided by Promess Inc. of Brighton,Michigan.

The control uses a technology called signature analysis to evaluate the inputs provided by the torque monitor.