Single-Lip Gun Drill Rake Face for Regrinding and Hole Accuracy
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Solution Overview
Problem
Existing single-lip drills face challenges in achieving low center line values and high regrindability while maintaining hole quality, due to complex and expensive production processes, limited regrind cycles, and high wear on cutting edges.
Innovation Solution
The design modifies the single-lip drill by adding additional surfaces on the chip surface that extend axially and modifying the rake face, allowing for production with simple grinding wheels and reducing the need for specialized tools, enabling easier and more cost-effective manufacturing and regrinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complex rake face structures are used to improve chip formation, then chip formation quality is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The rake face is segmented into multiple zones with different functions: a wear-resistant coating zone at the cutting edge, a chip formation zone with specific geometry, and a clearance zone. This segmentation allows each zone to be optimized independently while simplifying the overall manufacturing process by using standard grinding wheels for each segment.
Solution Approach 2:
Different regions of the rake face are given different properties: the cutting edge area receives a wear-resistant coating (TiN, TiCN, or TiAlN) while other areas have different surface finishes or geometries. This local differentiation improves chip formation and tool life without requiring complex structures across the entire rake face.
2Manufacturing precision
If wide chip formers are used to improve chip formation, then chip formation is improved, but regrinding time and cost increase significantly
Solution Approach 1:
The chip former function is extracted from the main rake face geometry and implemented as a separate, narrow feature. This allows the chip formation function to be maintained while minimizing the material that needs to be removed during regrinding, thus reducing regrinding time and cost.
Solution Approach 2:
Instead of using a wide chip former that covers most of the cutting edge, a narrow chip former is used that provides sufficient chip formation control for the specific application. This partial action approach maintains adequate chip formation while significantly reducing regrinding requirements.
3Manufacturing precision
If multiple specialized grinding wheels are used to achieve precise rake face geometry, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The rake face geometry is designed to be compatible with standard, universally available grinding wheels rather than requiring specialized custom wheels. The geometric features are configured so that conventional grinding equipment can achieve the required precision, making the manufacturing process more economical and accessible.
4Ease of manufacture
If the secondary cutting edge is positioned on the rake face plane, then manufacturing is simplified, but chip removal efficiency decreases
Solution Approach 1:
The secondary cutting edge is positioned in a different spatial dimension relative to the rake face plane - specifically, it is offset axially to create a stepped configuration. This dimensional change allows the secondary edge to effectively break up chips and improve chip removal without complicating the manufacturing process, as the offset can be achieved with standard grinding operations.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a single-lip drill (1) with an inner (23.1) and an outer (23.2) rake face. Very good middle course values and endurance are obtained with the polished face according to the invention.