Thread Forming Tap Lobes to Prevent Crest Chipping
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Solution Overview
Problem
Thread forming taps experience machining defects due to chipping of incomplete thread crests when they contact the inner surface of a pilot hole, leading to friction and chip entrapment.
Innovation Solution
The thread forming tap design includes lobes protruding in radial directions and reliefs with smaller diameters, along with an inclined surface on the incomplete thread portion, preventing contact with the pilot hole and reducing friction, thereby minimizing chipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the incomplete thread is beveled along the circumference direction to remove crests, then the thread forming tap can be manufactured, but the crest is pressed against the inner circumferential surface of the pilot hole causing friction and chipping
Solution Approach 1:
The invention applies asymmetry by designing the incomplete thread portion with lobes having different radial heights, where at least one lobe has a greater radial height than others. This asymmetric configuration allows the higher lobe to engage with and deform the inner circumferential surface of the pilot hole, preventing the thread crest from contacting the pilot hole surface and causing chipping.
Solution Approach 2:
The invention applies local quality by creating a specific structural feature (lobes with varying radial heights) at a localized position (the incomplete thread portion) rather than uniformly modifying the entire thread. The lobe with greater radial height performs the specific function of preventing crest contact, while other portions maintain their original functions.
2Ease of operation
If the incomplete thread crest contacts the inner circumferential surface of the pilot hole, then the thread forming tap can engage the pilot hole, but friction increases and chips are generated causing machining defects
Solution Approach 1:
The invention applies parameter changes by modifying the geometric parameters of the incomplete thread portion, specifically creating lobes with different radial heights. The lobe with greater radial height changes the contact parameters between the thread and pilot hole, enabling it to engage the pilot hole surface first and prevent harmful friction and chip generation.
3Device complexity
If the crest of the incomplete thread is formed on the curved surface around the axis, then the thread structure is simplified, but the crest is more susceptible to chipping due to friction with the pilot hole
Solution Approach 1:
The invention resolves this contradiction by introducing asymmetry in the form of lobes with different radial heights on the incomplete thread portion. This asymmetric design adds minimal structural complexity while significantly improving the strength and durability of the incomplete thread by preventing crest chipping through engineered engagement with the pilot hole surface.
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 configuration enhances deformation of the pilot hole surface while reducing friction and chipping, thus minimizing machining defects in internal threads.
Implementation Method 1
the lobes can deform the inner circumferential surface of the pilot hole
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(b)
AI summary
Provided is a thread forming tap that can suppress internal thread processing defects. A partial thread (33) is provided, in the axis (O) direction view, with a protrusion (33a) formed so as to protrude in the radial direction and a clearance section (33b) formed so as to have a smaller diameter than the protrusion (33a), and as a result of the foregoing, if a thread forming tap (1) rotates in a state where the inner circumferential surface of a pilot hole and the partial thread (33) come into contact, the protrusion (33a) of the partial thread (33) can be caused to engage with the inner circumferential surface of the pilot hole (an effect similar to thread being formed in the inner circumferential surface of the pilot hole by the screw thread of an engagement section (31) can be protruded). Due to this configuration, rubbing in a state where the partial thread (33) is pressed against the inner circumferential surface of the pilot hole can be suppressed, and as a result, chipping of the partial thread (33) can be prevented. Accordingly, it is possible to prevent fragments of the partial thread (33) from catching in the area between the inner circumferential surface of the pilot hole and the screw thread of the thread forming tap (1), enabling suppression of internal thread processing defects.