Internal Thread Forming Tool Relief Geometry for Lower Axial Stress
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Solution Overview
Problem
The existing method for forming internal threads using percussion tapping tools experiences excessive stress on the tool due to axial forces during the deceleration phase, leading to reduced tool life and potential breakage.
Innovation Solution
A tool with a thread generating region featuring flank relieved surfaces and a thread and clearing tooth configuration that reduces friction and stress by allowing the thread tooth to move freely during the deceleration and reversing phases, forming a peripheral groove without radial advancement and ensuring the thread is formed without damaging the tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the tool decelerates during the groove forming stroke, then the thread pitch can be reduced to form an encircling groove, but axial forces occur on the thread cutting teeth causing stress and reduced tool life
Solution Approach 1:
The patent applies dynamics by making the thread cutting tooth geometry adaptable during operation. The tooth is designed with a relief surface that allows it to assume different positions relative to the workpiece during deceleration. This dynamic positioning capability enables the tooth to form grooves at variable pitch while managing the axial forces through controlled engagement and disengagement, thereby maintaining tool reliability during pitch adaptation.
2Manufacturing precision
If the thread cutting tooth remains in continuous engagement with the workpiece, then a continuous flight is produced, but friction and stress increase during deceleration and reversing movements
Solution Approach 1:
The patent implements beforehand cushioning through the relief surface geometry on the thread cutting tooth. This relief surface is designed in advance to provide a gradual disengagement path during deceleration and reversing movements. By preparing this cushioning geometry beforehand, the tooth can smoothly transition from engaged to disengaged state, reducing friction forces and stress while maintaining the continuity of the formed thread flight.
3Productivity
If the axial feed rate is reduced during deceleration, then the encircling groove can be formed, but the thread cutting teeth experience excessive stress
Solution Approach 1:
The patent applies local quality by providing different surface characteristics on different parts of the thread cutting tooth. The relief surface is specifically designed with particular geometric properties that differ from the cutting edge region. This localized quality difference allows the tooth to handle axial forces differently during groove formation versus active cutting, enabling the encircling groove to be formed while protecting the tool strength through the specially designed relief surface geometry.
Data Source
AI summary
A thread forming tool comprises a thread generating region that extends along a helical line with a thread pitch angle and a thread direction of the thread to be formed and has an active profile corresponding to the thread profile of the thread to be formed, wherein the thread generating region has a thread tooth having a thread profile with a front thread tooth profile flank and a rear thread tooth profile flank, has a front flank relieved surface, adjoining the front thread tooth profile flank and has a rear flank relieved surface, adjoining the rear thread tooth profile flank, wherein the front flank relieved surface is isolated relative to a front thread tooth flank envelope, wherein the rear flank relieved surface is displaced relative to a rear transverse plane wherein the helical line is inclined to the rear relative to the rear transverse plane by the thread pitch angle.