Thread Forming Tap Geometry for Lower Leading Flank Pressure
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Solution Overview
Problem
Thread forming taps experience reduced durability and tool life due to excessive pressure on the leading flank during tapping operations, leading to premature wear and inadequate thread formation.
Innovation Solution
The thread forming tap design features a leading portion with a larger pitch than the complete thread portion, where the leading flank has a smaller indentation depth than the trailing flank, and a symmetrical isosceles triangular screw thread profile, reducing pressure on the leading flank and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thread forming tap uses a conventional screw thread design with equal indentation depth for leading and trailing flanks, then the thread formation is complete and effective, but the leading flank experiences excessive pressure causing premature wear and reduced tool life
Solution Approach 1:
The patent applies asymmetry by designing the screw thread with different indentation depths for the leading flank and trailing flank. Specifically, the leading flank is designed with a smaller indentation depth than the trailing flank, creating an asymmetric thread profile that redistributes the pressure during the tapping operation. This asymmetric design reduces the excessive pressure concentrated on the leading flank, thereby suppressing wear and extending tool life while still achieving complete thread formation.
2Reliability
If the leading portion has the same pitch as the complete thread portion, then the thread formation is straightforward, but the leading flank receives excessive reaction force causing wear and reduced durability
Solution Approach 1:
The patent applies local quality by giving different pitch values to different portions of the thread. The leading portion is designed with a larger pitch than the complete thread portion, creating a local variation in thread geometry. This local pitch increase in the leading portion reduces the indentation depth and reaction force on the leading flank during engagement, thereby reducing wear and improving durability, while the complete thread portion maintains the standard pitch for proper thread formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces the pressure on the leading flank, thereby extending the tool life and durability of the thread forming tap by minimizing wear and maintaining effective thread formation.
Implementation Method 1
cause an inner circumferential surface of the prepared hole to be plastically deformed for thereby forming an internal thread corresponding to the external thread provided in the complete thread portion
Data Source
AI summary
A thread forming tap including a complete thread portion and a leading portion is to be screwed into a prepared hole provided in a workpiece so as to cause an inner circumferential surface of the prepared hole to be plastically deformed for thereby forming an internal thread corresponding to the external thread provided in the complete thread portion. A screw thread of the external thread has a leading flank and a trailing flank, which are to be positioned on a front side of the trailing flank and on a rear side of the leading flank, respectively, when the thread forming tap is screwed into the prepared hole. The screw thread is shaped such that, in the leading portion, an indentation depth into the workpiece made by the leading flank is smaller than an indentation depth into the workpiece made by the trailing flank.