Analysis of the cutting and forming tapping in holes produced by plasma cutting and helical drilling

All mechanical components in modern industry have at least one threaded part, enabling their assembly and disassembly. Threads are essential elements in engineering because they can provide not only accurate assembly but also power transmission. However, manufacturing thread parts can show several challenges in some situations due to the numerous parameters that must be met. Hardness of materials, coating, tap geometry, and initial hole diameter are some basic input parameters that should be analysed before starting the manufacturing process. Based on that, a study was developed to analyse the influence of the initial hole in forming and cutting tapping standard M8. The holes manufactured by plasma cutting and helical milling, aiming to monitor the thrust force, torque, and the influence of form errors in the threaded holes. According to the results, the roundness error for the pre-drilled holes produced by the plasma-cutting process was 442.81 μm. In comparison, pre-drilled holes produced by the helical milling process had an error of 73.12 μm. This situation demonstrated a roundness error 6 times greater for the pre-drilled holes made by plasma cutting. Furthermore, the results of the threading process applied to the holes manufactured by plasma-cut drilling were more significant for the forming process than for the cutting process. Considering the variation in torque values, the highest was 27.02 N.m for the forming tapping, and the lowest was 4.59 N.m for the cutting tapping. Considering the thrust force, the highest value found was 302.5 N for the forming tapping, and the lowest value was 75.5 N, also for the forming tapping. Finally, plasma cutting and drilling can be another promising strategy for production aspects of the threading process. However, it should be noted that the type of pre-drilling process results in higher torque and thrust force during tapping, especially during forming tapping.