Sharp-Crest Thread Forming Tap for Lower Tapping Torque
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Solution Overview
Problem
The existing thread forming taps generate high torque during tapping operations, leading to reduced tool life due to wear and breakage, as the thread ridge bites into the workpiece's inner-wall-surface layer, causing significant rotational resistance.
Innovation Solution
A thread forming tap with a triangular-shaped thread ridge in the leading portion, featuring a sharp crest with side surfaces inclined at angles greater than the flank angle, which reduces torque and enhances strength by allowing even displacement of material, thereby minimizing thrust load and extending tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thread ridge bites into the inner-wall-surface layer portion to form an internal thread, then the internal thread is successfully formed, but a large torque is generated causing reduced tool life
Solution Approach 1:
The thread ridge is designed with different geometric properties in different regions: the top portion has a sharp crest with high curvature radius to concentrate stress and facilitate material displacement, while the flanks have smaller curvature radii to reduce contact area and torque. This local differentiation allows effective thread formation at the crest while minimizing wear and torque generation along the flanks, thereby extending tool life.
Solution Approach 2:
The invention optimizes specific geometric parameters of the thread ridge, including the curvature radius of the top portion (R1) being larger than that of the flanks (R2), and the flank angle (α) being within 30-60 degrees. These parameter changes create a thread ridge that efficiently displaces material with reduced rotational resistance, solving the contradiction between thread formation effectiveness and tool life.
2Device complexity
If the thread ridge has a conventional shape, then the structure is simple, but the torque during tapping is large causing wear and breakage
Solution Approach 1:
The thread ridge incorporates a localized sharp crest at the top portion with a larger curvature radius, while maintaining simpler geometry at the flanks with smaller curvature radii. This local quality differentiation creates an optimized stress distribution that reduces torque and prevents breakage without significantly complicating the overall structure, thereby improving reliability while keeping device complexity manageable.
3Ease of operation
If the flank angle is small, then the thread ridge is sharper for better material displacement, but the strength of the thread ridge is reduced
Solution Approach 1:
The invention optimizes the flank angle (α) within the range of 30-60 degrees, which provides an optimal balance between material displacement capability and structural strength. Additionally, the top portion curvature radius (R1) is designed to be larger than the flank curvature radius (R2), creating a sharp crest for effective material displacement while maintaining sufficient strength through the optimized geometric parameters.
Solution Approach 2:
The thread ridge features a sharp crest at the top portion with larger curvature radius for enhanced material displacement, while the flanks have smaller curvature radii and optimized angles to maintain structural strength. This local quality differentiation allows the thread ridge to be sharp where needed for operation while remaining strong overall to prevent breakage.
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 triangular cross-sectional shape of the thread ridge reduces torque and thrust load during tapping, ensuring sufficient tool life by distributing material displacement evenly and maintaining strength, with optimal results achieved when inclination angles range from 40° to 80° and internal angles from 80° to 160°.
Implementation Method 1
the protruding portions of the external thread are caused to bite into an inner-wall-surface layer portion of the prepared hole, so as to cause the inner-wall-surface layer portion to be plastically deformed for thereby forming an internal thread
Implementation Method 2
a large torque (rotational resistance) is generated... by reducing a torque in the tapping operation
Data Source
AI summary
A thread forming tap including a complete thread portion and a leading portion that are provided with an external thread. A thread ridge of the external thread has, in an axial cross section, a triangular shape that is defined by a pair of flanks located on respective opposite sides in an axial direction, such that each of the flanks is inclined by a predetermined flank angle corresponding to a shape of a valley of an internal thread to be formed. A sharp crest is provided in a top portion of the thread ridge at least in the leading portion, and has, in the axial cross section, a triangular shape that is defined by a pair of side surfaces located on respective opposite sides in the axial direction, such that each of the side surfaces is inclined by an inclination angle that is larger than the flank angle.