Tapping Tool Broaching Groove Reduces Thread Profile Stress
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Solution Overview
Problem
The existing methods for producing threaded holes often result in excessive cutting load on the thread profile, leading to chipping or tool breakage due to the sudden reduction in tapping speed during the tapping process.
Innovation Solution
The method employs a tapping tool with a broaching blade that forms a peripheral groove without thread pitch, allowing the thread profile to rotate stress-free, reducing mechanical stress and enabling a controlled reversal stroke without excessive cutting edge stress, and optionally includes a flute form stroke to extend the tapping depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the tapping speed is reduced to 0 at the end of the tapping stroke, then the tapping process can be completed, but excessive cutting load occurs on the thread profile causing chipping or tool breakage
Solution Approach 1:
A broaching groove is formed in advance during the tapping stroke before the reversing stroke begins. This groove provides a stress-free path for the thread profile during reversal, preventing tool breakage when the tapping speed is reduced to 0 or reversed.
Solution Approach 2:
The tool profile is segmented into two functional parts: thread cutting teeth for creating the internal thread, and broaching blades for forming the peripheral groove. This segmentation allows each part to perform its specific function without interfering with the other, enabling both thread creation and stress-free reversal.
2Productivity
If a single-shot tapping tool is used to drill core hole and cut internal thread in one stroke, then process time is reduced, but tool load increases causing excessive stress on the thread profile
Solution Approach 1:
The single-shot tool is segmented into multiple functional elements: main cutting edge for core hole drilling, thread cutting teeth for internal thread creation, and broaching blades for groove formation. This segmentation allows the tool to perform multiple operations simultaneously while distributing the cutting load across different elements.
Solution Approach 2:
The core hole drilling and internal thread cutting operations are merged into a single tapping stroke, performed simultaneously by the main cutting edge and thread cutting teeth respectively. This combining of operations reduces total process time while the broaching groove provides relief for the combined tool load during reversal.
3Reliability
If the thread profile rotates in the broaching groove during reversing stroke, then stress on the thread profile is reduced, but an additional groove-forming step is required
Solution Approach 1:
The groove-forming function is merged into the main tapping tool by adding broaching blades to the tool profile. The groove is formed simultaneously with the thread cutting during the same tapping stroke, eliminating the need for a separate groove-forming step and reducing overall process complexity.
Solution Approach 2:
The tapping tool is designed with multi-functionality: it can drill the core hole, cut the internal thread, and form the broaching groove all in one stroke. This universal tool eliminates the need for separate operations and reduces device complexity despite the additional functional requirements.
Data Source
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AI summary
The invention relates to a method for producing a threaded hole (1) in a workpiece (5) by means of a thread tapping tool (23), which has at the tapping tip (25) thereof a main cutting edge (27) and a thread profile (29), which lags in a thread tapping direction (I) and has at least one thread cutting tooth (41, 42, 43, 44), wherein, in a thread tapping stroke (G), the main cutting edge (27) produces a core hole and at the same time the thread profile (29) forms an internal screw thread (9) on the inner wall of the core hole until a target thread depth (tG) is achieved, specifically at a thread tapping advancement (fG) in the thread tapping direction (I) and a thread tapping rotational speed (nG) of the thread tapping tool (23) synchronized with said thread tapping advancement, wherein, after the thread tapping stroke (G), an opposite reversing stroke (R) is performed, in which the thread tapping tool (23) is removed from the threaded hole in a reversing direction (II), specifically with an opposite reversing advancement (fR). According to the invention, the thread profile (29) has at least one broaching cutting edge (46, 48, 50, 52). During the reversing stroke (H), a broached groove (R1 to R4) is produced by means of the broaching cutting edge (46, 48, 50, 52), through which broached groove the thread cutting tooth (41, 42, 43, 44) is removed from the threaded hole (1) in a stress-free manner.