Contact Type Thread Tester for Tap Inspection Automation

In this paper, we introduce a contact type thread tester which can automatically sort out bad thread holes. The existing non-contact type testers used eddy current, camera, ultrasonic, etc. However, non-contact type testers are vulnerable to noise. In this paper, a contact type inspection method is used to sort out the defects of the thread by measuring the reverse torque that occurs while tightening the bolt and threaded holes. This tester is insensitive to noise, such as vibration. We can inspect a thread hole regardless of the size of the hole. Also, the tester automatically aligns bolt and thread hole positions in order to remove the positional error. The tester checks the size of the thread hole using a camera, and automatically carries out the inspection with the optimum torque associated to the hole size. In addition, we develop a smartphone application to control the tester remotely.