Thread Forming Tap Back-Taper Blade to Prevent Thread Crest Rubbing
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Solution Overview
Problem
The existing thread forming taps experience a rubbing phenomenon when reversed, leading to deformation of the female thread crests and abrasive wear on the inside diameter finishing blade.
Innovation Solution
The thread forming tap design includes an inside diameter finishing blade with a back taper, where the height on the chamfer portion side is lower than the height on the complete thread portion side, reducing interference with the female threads during reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the inside diameter finishing blade has a uniform diameter along its length, then the blade can effectively finish the inside diameter of the female thread, but the blade causes rubbing phenomenon and deformation of thread crests during reverse rotation
Solution Approach 1:
The inside diameter finishing blade is designed with non-uniform diameter along its length, where the diameter varies from the tip to the base. Specifically, the blade has a smaller diameter at the tip portion and a larger diameter at the base portion, creating different functional zones. This local variation in geometry allows the blade to perform finishing operations effectively while avoiding harmful rubbing during reverse rotation, as the tapered design prevents the blade from contacting the formed threads during withdrawal.
2Strength
If the inside diameter finishing blade contacts the female thread during reverse rotation, then the blade can maintain structural integrity, but the blade creates abrasive wear and workpiece adhesion
Solution Approach 1:
The harmful contact between the inside diameter finishing blade and the female thread during reverse rotation is eliminated by designing the blade with a tapered geometry that prevents such contact. The extraction principle is applied by removing the problematic interaction entirely - the blade is shaped so that only the necessary portion contacts the workpiece during forward cutting, while the reverse rotation occurs without contact, thereby eliminating abrasive wear and workpiece adhesion.
3Productivity
If the chamfer portion of the inside diameter finishing blade has the same diameter as the complete thread portion, then the blade can finish threads throughout its length, but the chamfer portion causes rubbing phenomenon when reversed
Solution Approach 1:
The inside diameter finishing blade is designed with different diameters for different portions along its length. The chamfer portion has a different diameter than the complete thread portion, creating localized functional zones. This local quality variation ensures that the chamfer portion does not contact the formed threads during reverse rotation, eliminating the rubbing phenomenon while the complete thread portion continues to perform finishing operations effectively.
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 effectively reduces deformation of the female thread crests and minimizes friction and heat generation during both forward and reverse rotations of the thread forming tap.
Implementation Method 1
forms a female thread by plastically deforming a pilot hole in a workpiece
Implementation Method 2
cuts and removes a crest portion of the female thread
Implementation Method 3
minimizes friction and heat generation during both forward and reverse rotations
Data Source
Figure 1
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AI summary
A thread forming tap (1) is provided with a male thread portion (3), a groove, and an inside diameter finishing blade (61). A chamfer portion (31) of the male thread portion (3) is provided continuous with the complete thread portion (32) and decreases in diameter toward a tip end. The groove is provided parallel to a shaft center spanning the complete thread portion (32) and the chamfer portion (31) so as to divide a thread (71) of the male thread portion (3). On the chamfer portion (31) and the complete thread portion (32), the inside diameter finishing blade (61) is provided along an open edge of the groove on the side opposite the rotational direction of the thread forming tap (1). The inside diameter finishing blade (61) cuts and removes a crest portion of the female thread formed on a surface layer of a pilot hole (90). The height of a first step finishing blade (611) of the inside diameter finishing blade (61) on the chamfer portion (31) is lower than the height of a second step finishing blade (612) of the inside diameter finishing blade (61) formed on a portion corresponding to a thread (71) on the tip-most end of the complete thread portion (32).