Tapping Tool Bit Stress Reduction via Reversing Stroke
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Solution Overview
Problem
Existing methods for producing threaded bores often result in excessive cutting stress on the tool bit, leading to breakage or thread profile damage due to sudden reduction in tapping speed during the tapping process.
Innovation Solution
The method involves a groove forming step after the tapping stroke, where a pitch-free encircling groove is created, allowing the thread profile to rotate stress-free, and the tapping speed to be reduced to zero without excessive cutting lip stress, enabling the production of an encircling thread countersink and reducing tool bit stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the tapping speed is reduced to zero at the end of the tapping stroke, then the thread cutting process can be completed, but excessively large cutting stress occurs on the thread profile leading to tool bit breakage or cutting teeth failure
Solution Approach 1:
The tapping process is divided into two distinct phases: a tapping stroke for thread cutting and a subsequent reversing stroke for tool withdrawal. This segmentation allows the thread to be formed at controlled tapping speed, then the tool is reversed to withdraw stress-free, avoiding the stress concentration that would occur from immediate speed reduction to zero.
Solution Approach 2:
The tool bit performs dynamic motion with synchronized tapping speed and feed during thread cutting, then transitions to a reversing stroke with opposite feed and synchronized reversing speed. This dynamic approach allows controlled deceleration and stress-free withdrawal, preventing excessive cutting stress on the thread profile.
2Productivity
If the tapping feed and speed are reduced to zero immediately after the tapping stroke, then the thread cutting is completed, but the thread profile cannot rotate stress-free leading to cutting tooth breakage
Solution Approach 1:
The process separates thread cutting from tool withdrawal into distinct strokes. During the tapping stroke, feed and speed are synchronized for efficient thread formation. After reaching the intended thread depth, a reversing stroke is initiated where the tool withdraws in the opposite direction with synchronized reversing parameters, allowing the thread profile to rotate stress-free and preventing cutting tooth breakage.
Solution Approach 2:
The tool bit performs periodic motion with alternating tapping and reversing strokes. Each cycle includes forward motion for thread cutting and backward motion for stress-free withdrawal. This periodic action with synchronized speed and feed control ensures both productivity during cutting and reliability during the reversal phase.
Data Source
AI summary
A method for producing a threaded bore in a workpiece with a tapping tool bit, which, at its drill bit tip, has a main cutting lip and a thread profile trailing in a tapping direction (I) with at least one thread cutting tooth, wherein, in a tapping stroke (G), the main cutting lip produces a core hole and, at the same time, the thread profile forms an internal thread at the inner wall of the core hole until reaching an intended thread depth (tG), specifically with a tapping feed (fG) in the tapping direction (I).