Thread-Forming Tap Margin Geometry for Torque Reduction
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Solution Overview
Problem
Conventional thread forming taps fail to sufficiently reduce working torque and extend tool life, as existing techniques do not effectively minimize contact area during machining.
Innovation Solution
The thread forming tap features screw threads with margin portions projecting radially and relief portions of smaller diameter, forming a ridge line shape with a width dimension of zero from the thread bottom to the effective diameter position, and a helix angle opposite to the screw thread twist, within the range of 0.5α≤β≤1.5α, to reduce contact area and torque, and increase tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional thread forming taps with standard margin portions are used, then thread formation is achieved, but working torque is high and tool life is limited
Solution Approach 1:
The margin portions are designed with non-uniform width along the axial direction, creating local quality variations. The width is smaller in the radial direction at specific locations, reducing contact area with the workpiece at critical regions while maintaining thread formation capability. This localized geometric optimization reduces working torque and extends tool life.
Solution Approach 2:
The invention changes the geometric parameters of the margin portions, specifically the width dimension in the radial direction. By adjusting the width to be smaller at certain axial positions and introducing a helix angle different from the screw thread lead angle, the contact characteristics are modified, resulting in reduced working torque and improved tool life.
2Manufacturing precision
If margin portions with larger contact area are used, then thread formation quality is improved, but working torque increases
Solution Approach 1:
The margin portions exhibit local quality variations in their width along the axial direction. By making the width smaller in the radial direction at specific locations, the contact area is reduced to decrease working torque, while the overall thread formation quality is maintained through the distributed margin portion structure.
Solution Approach 2:
Instead of increasing margin portion width uniformly to improve thread formation quality, the invention inverts the approach by reducing the width at critical locations. This counterintuitive design reduces contact area and working torque while still achieving acceptable thread formation through the helical action and distributed margin portions.
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 significantly reduces working torque and increases tool life by minimizing contact area during machining, as demonstrated by tapping durability and torque comparison tests, with the helix angle equal to the lead angle providing the greatest tool life improvement.
Implementation Method 1
causes the margin portions of the screw threads to cut into a surface layer portion of a prepared hole formed in a work to plastically deform the surface layer portion so as to form female threads
Data Source
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AI summary
Provided is a thread-forming tap for reducing machining torque and improving tool service life. A thread-forming tap (10) for plastically deforming the surface-layer section of a prepared hole to form a female thread by causing a margin section (18) of a screw thread (16) to bite into the surface-layer section of the prepared hole formed in an object to be machined, the tap being provided with a screw thread (16) formed in the shape of a male thread while a margin part (18) provided protruding in the radial direction and a release part (20) with a diameter less than the margin part (18) are arranged in alternating fashion, wherein the margin part (18) is formed in a udgeline shape with a width dimension of 0 at least at the bottom (30) of the screw thread (16), whereby the contact surface area onto the object being machined can be minimized during machining, machining torque can be reduced, and tool service life can be improved.