Dual-Cutting-Edge Drill Geometry for Low-Rigidity Hole Accuracy
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Solution Overview
Problem
Conventional drills with continuously changing point and relief angles suffer from reduced accuracy and increased vibration when used with handheld tools, leading to suboptimal hole quality, especially when the spindle has low rigidity or accuracy.
Innovation Solution
A drill design featuring first and second cutting edges with continuously or intermittently decreasing point and relief angles, along with a deflection reducer to reduce vibration and improve hole quality, allowing for high-accuracy drilling in both rigid and low-rigidity drilling setups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a drill with continuously changing point angle and relief angle is used, then hole machining quality is improved and tool life is extended, but vibration increases and drilling accuracy deteriorates when used with handheld tools
Solution Approach 1:
The drill is divided into two distinct cutting edge sections: first cutting edges at the tip with continuously decreasing point angle and relief angle for initiating the hole, and second cutting edges at the rear end with constant point angle and relief angle for finishing the hole. This segmentation allows each section to perform its specialized function independently, resolving the contradiction between hole quality and drilling accuracy.
Solution Approach 2:
Different parts of the drill are given different geometric properties: the tip portion has continuously varying angles optimized for hole initiation, while the rear portion has constant angles optimized for hole finishing. This local differentiation ensures that each region of the drill performs optimally for its specific function, preventing the vibration and accuracy deterioration that would occur with a uniform geometry throughout.
2Reliability
If a drill with continuously decreasing point angle and relief angle is used, then wear resistance is improved, but the drill produces polygonal cross-sections instead of circular holes when used with low rigidity spindles
Solution Approach 1:
The drilling process is segmented into two stages performed by different cutting edges: the first cutting edges create the initial hole shape, and the second cutting edges with constant angles refine and circularize the cross-section. This segmentation ensures that the wear-resistant continuously varying geometry is used only where needed for hole initiation, while the constant-angle geometry handles the cross-section formation.
Solution Approach 2:
The point angle and relief angle parameters are changed continuously from the tip toward the rear end for the first cutting edges, then held constant for the second cutting edges. This parameter variation strategy optimizes wear resistance at the tip while ensuring circular cross-sections are produced by the rear cutting edges with stable geometric parameters.
3Manufacturing precision
If a drill with continuously changing cutting edge geometry is used, then hole quality is improved, but the complexity of the drill structure increases
Solution Approach 1:
The complex continuously varying geometry is confined to only the first cutting edges at the tip, while the second cutting edges use simpler constant geometry. This segmentation reduces the overall structural complexity compared to having continuously varying geometry throughout the entire drill, while still achieving high hole quality where it is most critical.
Data Source
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AI summary
According to one embodiment, a drill includes the first cutting edges, the second cutting edges and a deflection reducer. The first cutting edges drill a prepared hole to a workpiece. The first cutting edges are formed in a tip side of the drill. The first point angle and each first relief angle of the first cutting edges continuously or intermittently decrease from the tip side toward a rear end side of the drill. The second cutting edges finish the prepared hole. The second cutting edges are formed at positions away in the rear end side from the first cutting edges. The second cutting edges have the second relief angles at a maximum diameter position. The deflection reducer reduces deflection of the second cutting edges. The deflection reducer is formed between the first cutting edges and the second cutting edges. The deflection reducer is inserted into the prepared hole.