Drill Tool Hard Material Insert Concave Recess Wear Compensation
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Solution Overview
Problem
Drilling tools with hard material inserts experience varying drilling speeds due to wear-related changes in the clearance angle, making it difficult to determine the remaining service life and leading to inconsistent performance.
Innovation Solution
A drilling tool design featuring a helical shank with a hard material insert having radially extending cutting edges and concave recesses with linearly increasing depth, maintaining a constant rake angle and compensating for wear through widening recesses, along with reinforcing ribs for enhanced robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If concave recesses with spherical shape are used to increase clearance angle, then drilling speed is improved, but the clearance angle varies greatly over service life due to wear, causing inconsistent drilling speed
Solution Approach 1:
The patent uses concave recesses with curved surfaces to increase the clearance angle. The specific curvature profile is designed so that as the cutting edge wears and moves into the recess, the clearance angle increases in a controlled manner that maintains consistent drilling performance throughout the service life.
Solution Approach 2:
The patent changes the geometric parameters of the concave recesses, specifically their depth, width, and curvature radius, to optimize the clearance angle progression during wear. By carefully selecting these parameters, the design ensures that the clearance angle evolves in a way that compensates for wear while maintaining stable drilling speed.
2Speed
If uniform increased rake angle is applied to increase drilling speed, then drilling speed is improved, but the robustness of the hard material insert against rebar hits is weakened
Solution Approach 1:
The patent applies different rake angles to different regions of the cutting edge. The concave recesses create local areas with increased rake angle that improve drilling speed, while other regions maintain lower rake angles that provide robustness against impacts from rebar. This localized differentiation resolves the contradiction between speed and strength.
Data Source
Figure 1a~4
AI summary
The tool (1) has a helical shaft (2) with a hard material insert (3) fastened at an axial shaft end in a positive-fit manner, where the insert has a radially extending cutting edge (4a, 4b), which adjoins a tangential bent-free surface (6a, 6b). The bent-free surface has a concave recess (7) with a breadth (B) extending longitudinal to the cutting edge, length (L) and width (T) perpendicular to the cutting edge. The width increases linearly with the length based on the cutting edge, where the recess is extended in its breadth linear to the length. USE : Drill tool i.e. percussion drill bit, for use with a hand-machine tool for drilling rock and concrete. ADVANTAGE : The width of the concave recess increases linearly with the length based on the cutting edge, thus ensuring that same radially local clearance angle and same drilling speed are obtained over the service life of the tool. DESCRIPTION OF DRAWINGS : The drawing shows a side view of a drill tool. B : Breadth L : Length T : Width 1 : Drill tool 2 : Helical shaft 3 : Hard material insert 4a, 4b : Cutting edge 6a, 6b : Bent free surface 7 : Concave recess.