Abstract
The shearing of the chips in a blind hole thread presents a particular problem in machining industry. The tap geometry plays an important role in the tool's durability, influencing the forces during the tapping process and also the way in which the chips are evacuated. This paper analyzes the influence of the tap geometry on the cutting of materials such as C45, 42CrMo4 and X5CrNi8. An adequate geometry will extend the tap durability by controlling the chip when the tap reverses while still engaged in the tapping process. It relates to the improvement of a spiral tap drill, which discharges chips towards the shank via a helical flute. The article contains details about the tap geometries and the results obtained in this research. Based on the results obtained in this research, the purpose of this paper was achieved. The tap durability was improved, the chip deposition on the rake surface was reduced and the torsion torque has a smaller value compared to the standard tap geometry.
Highlights
Internal thread tapping is one of the most demanding machining operations
By adding an increased core diameter for the tap with reduced diameter, the tool life is increased by approximately 30%
By adding two guide lands, the relief on flanks is doubled and there is no outside relief for reduced exterior diameter, which leads to a substantial increase of the tool life compared to the standard tap
Summary
Internal thread tapping is one of the most demanding machining operations. One of the major problems in the process is tap breakage, resulting from excessive torque. Since tapping is often among the final operations performed on a workpiece, tap breakage is extremely costly. Other problems associated with the tapping process include thread dimensional accuracy, thread form error, and surface roughness of thread forms. [3] This article aims to research the cutting tool geometry. The tap geometry is very important for the tool’s life, influencing the forces that act upon the tap during cutting as well as the way the chips are removed. Chip removal is an important factor in the process of threading blind holes.
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