Spiral Tap Flute Geometry for Tear-Free Tapered Pipe Threads
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Solution Overview
Problem
Existing pipe-tapered-thread machining taps experience issues with tearing and cutting edge mark formation in machined internal threads, particularly when working with materials like stainless steel or low carbon steel, due to small cutting edge amounts and chip clogging.
Innovation Solution
A spiral tap design featuring spiral flutes with a helix angle between 30° and 50° and a flute width ratio of 0.3-0.5, along with a surface treatment using a titanium carbonitride TiCN film, to enhance tool durability and prevent tearing and cutting edge mark formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thread cutting is performed by the complete thread portion with both crest and root, then larger cutting resistance is generated, but tap breakage and chipping occur more easily
Solution Approach 1:
The patent changes the geometric parameters of the complete thread portion by setting the thread cutting depth to 0.05-0.15 times the major diameter of the internal thread and the thread cutting width to 5-15 degrees. These parameter optimizations balance the cutting resistance with tool strength, preventing tap breakage while maintaining machining efficiency.
2Manufacturing precision
If the amount of cut by one cutting edge is small (about 5μm), then the cutting edges are rubbed on the inner circumferential surface, but tearing and surface roughening occur
Solution Approach 1:
The patent optimizes the thread cutting depth parameter to 0.05-0.15 times the major diameter, which increases the amount of cut by each cutting edge from the conventional 5μm to a larger value. This parameter change reduces the rubbing effect on the inner circumferential surface and prevents tearing, thereby improving surface quality.
3Manufacturing precision
If cutting chips are bitten into the gap between back edge and inner circumferential surface, then indentation marks are formed, but sealing performance is reduced
Solution Approach 1:
The patent sets the thread cutting width to 5-15 degrees, which optimizes the geometry of the complete thread portion. This parameter change prevents cutting chips from being bitten into the gap between the back edge and inner circumferential surface, eliminating indentation marks while maintaining sealing performance.
4Productivity
If a conventional spiral tap design is used, then chip clogging occurs, but the patent proposes spiral flutes with specific helix angle and flute width ratio to prevent it
Solution Approach 1:
The patent specifies a helix angle of 30-50 degrees and a flute width ratio of 0.3-0.5 for the spiral flutes. These parameter optimizations improve chip evacuation capability, preventing cutting chip clogging while maintaining high machining efficiency.
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
The proposed spiral tap design effectively reduces tearing and cutting edge mark formation in machined internal threads, improving machining efficiency and tool durability, especially when working with challenging materials.
Implementation Method 1
surface treatment using a titanium carbonitride TiCN film
Implementation Method 2
surface treatment using a titanium carbonitride TiCN film
Implementation Method 3
spiral flutes with a helix angle between 30° and 50°
Data Source
Figure 1
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AI summary
Provided is a pipe-tapered-thread machining spiral tap that restrains occurrence of tearing and formation of cutting edge mark in the machined internal thread upon stop of rotation of the tap. The pipe-tapered-thread machining spiral tap 10 has three, four or five spiral flutes 20 each having a helix angle β of not smaller than 30° and smaller than 50°. A flute width ratio AG/(AG+AL) is 0.3-0.5, where AG represents a central angle which is subtended by each of the spiral flutes 20 and which is defined at a center corresponding to a rotation axis C in a cross section that is perpendicular to the rotation axis C, and AL represents a central angle which is subtended by each of the lands 22 and which is defined at the center corresponding to the rotation axis C in the cross section. Thus, it is possible to obtain the pipe-tapered-thread machining spiral tap 10 in which occurrence of tearing is restrained owing to presence of the spiral flutes 20 each having the helix angle β that is not smaller than 30° and smaller than 50°, and in which formation of mark of the cutting edge in the machined internal thread upon stop of rotation of the tap is retrained owing to a short distance between the cutting edge 24 and the back edge 26.