A study of contact interface and wear diagnosis for hand taps using ultrasonic method

•A novel contact image for hand taps was disclosed in this study.•An experiment was presented to measure the multi-point contact of tap tools.•The 2D and 3D contact images for hand taps were shown in the figures.•The comparison of contact area and contact pressure between the used and new hand taps was presented.•A 3D contact image can be obtained by using signal data processing.

This work was to study the contact interface between a set of used hand taps and another new one based on the regional scanning of ultrasound. The contact image was a novel disclosure for hand taps contact. The objective of this work was to provide a wear diagnosis by making a comparison of contact area between the used and the new hand taps. The 2D maps showed an apparent change not only in area sizes but also in contact shapes between the used and the new hand taps. The 3D contact images also provided useful information to show the degree of contact.The contact area between the tap and the workpiece was calculated using an image analysis software package. The range of contact areas varied from 2.49 mm2 to 35.31 mm2 for the used hand taps and from 1.19 mm2 to 28.55 mm2 for the new taps, depending on the definition of the contrast ratio. The result provided another scientific data for users to decide a correct timing for the tool replacement. In addition, maps of reflection coefficient and pressure contour distribution were presented. The range of contact pressure varied from 2.5 Mpa to 4.2 Mpa.