Drill Point Thinning for Self-Centering
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Solution Overview
Problem
Drilling tools with crossed or S-shaped point thinning suffer from poor self-centering capability due to the obtuse angle between the residual chisel edge and the main cutting edges, leading to increased working pressure and risk of lateral displacement during drilling.
Innovation Solution
A drilling tool design featuring a chisel edge with a residual chisel edge angle between -15° and +15° relative to a connecting line, and a point thinning region with specific geometrical features such as a triangular cross-section and symmetrical curvature, which improves self-centering without compromising stability or drilling quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If crossed or S-shaped point thinning is applied to shorten the chisel edge, then the self-centering capability is improved, but the angle between the residual chisel edge and main cutting edges becomes highly obtuse (130°-160°), causing poor self-centering behavior
Solution Approach 1:
The patent changes the geometric parameters of the chisel edge by defining a specific angle range (20°-40°) between the residual chisel edge and the connecting line of cutting edge corners, and controlling the length ratio (0.1-0.5) of the residual chisel edge relative to the main cutting edge length. This parameter optimization resolves the contradiction by achieving good self-centering capability while avoiding the highly obtuse angle problem of conventional point thinning.
2Ease of operation
If the chisel edge angle is reduced to 10° to improve self-centering, then the self-centering capability improves, but the point thinning is drawn into the region of the main cutting edge, causing the rake angle to become too small
Solution Approach 1:
The patent defines the residual chisel edge angle within a specific range (20°-40°) and controls its length to be 0.1-0.5 times the main cutting edge length. This prevents the point thinning from extending into the main cutting edge region and maintains an adequate rake angle, while still achieving improved self-centering capability.
Data Source
AI summary
A rotatable drilling tool has cutting edges (on a face side) that merge inwardly into a chisel edge, with the chisel edge(s) running on the face side about a central region surrounding the tool axis, with the chisel edges forming, in the innermost region (or about a point thinning region), a residual chisel edge, with cutting edge corners being formed at the outer ends of the main cutting edges, with a straight connecting line that runs through two cutting edge corners of main cutting edges situated opposite one another in relation to the tool axis, or if an opposite main cutting edge is not present, through a cutting edge corner and the tool axis, with the chisel edge inner region running from the outer end of the residual chisel edge within a region with an angle of between −15° and +15° in relation to a parallel to the connecting line.