Spiral Flute Tap Geometry for Carbide Chipping
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Solution Overview
Problem
Spiral fluted cutting taps made from cemented carbides like cobalt-tungsten carbide experience chipping and breakage when cutting small-diameter threaded holes due to the small included angles at the intersection of flutes and thread flanks, leading to reduced performance and tool life, especially in materials producing continuous chips.
Innovation Solution
A spiral fluted cutting tap design featuring a concave cutting face defined by a large radius, a concave core surface, a convex blending surface, and a convex heel surface, with a neutral chordal hook angle and optimized flute geometry to minimize chipping and enhance chip evacuation, manufactured from cobalt-cemented tungsten carbide with specific radii and coatings for improved durability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spiral fluted cutting taps made from cemented carbides are used to cut small-diameter threaded holes, then cutting speed and tool life are improved, but chipping and breakage occur due to small included angles at the intersection of flutes and thread flanks
Solution Approach 1:
The patent changes the geometric parameters of the flute by introducing a large radius concave cutting face and optimizing the included angle at the intersection of flutes and thread flanks. This parameter modification allows the use of cemented carbide materials while preventing chipping in small-diameter taps, thereby maintaining both high cutting speed and tool integrity
Solution Approach 2:
The patent utilizes cemented carbide composite material which combines hardness and wear resistance with sufficient toughness. This composite material enables the tap to withstand the mechanical stresses of cutting small-diameter holes while maintaining the geometric modifications needed to prevent chipping
2Ease of operation
If conventional high-speed steel spiral fluted taps are used, then chip evacuation is improved, but cutting speed is limited and tool life is reduced compared to cemented carbide
Solution Approach 1:
The patent optimizes the flute geometry parameters including the concave cutting face radius and helix angle to achieve effective chip evacuation. These geometric modifications allow cemented carbide taps to evacuate chips as effectively as high-speed steel taps while enabling much higher cutting speeds due to the superior material properties of cemented carbide
3Volume of moving object
If the included angle at the intersection of flutes and thread flanks is small, then the tap geometry is compact for small-diameter holes, but chipping occurs reducing tool life
Solution Approach 1:
The patent modifies the included angle parameter at the intersection of flutes and thread flanks to an optimized value that prevents chipping while maintaining compact tap dimensions suitable for small-diameter holes. This parameter optimization resolves the contradiction between compact size and tool life
Solution Approach 2:
The patent introduces a large radius concave cutting face that provides a curved transition surface at the flute intersection. This curvature reduces stress concentration and prevents chipping while maintaining the compact geometry needed for small-diameter taps, thereby extending tool life
Data Source
Figure 2
Figure 2A
Figure 3
AI summary
A cutting tool that includes an elongate body (22) that has a forward end (26) and a rearward end (24). The elongate body (22) has a fluted portion (30) that beginning near and extends in a rearward direction from the forward end (26). The fluted portion (30) has a flute (36, 38, 40, 42) that defines a cutting edge. The flute presents a concave cutting face (60) wherein the concave cutting face (60) is defined by a first radius (R1). The flute further presents a concave core surface (66) adjacent to the concave cutting face (60) wherein the concave core surface (66) is defined by a second radius (R2). The flute presents a convex heel surface (64) adjacent to the concave core surface (66) wherein the convex heel surface (64) is defined by a fourth radius (R4).