Segmented Drill Geometry for Circular Holes Under Low-Rigidity Drilling
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Solution Overview
Problem
Conventional drills with continuously changing point and relief angles suffer from reduced drilling quality and tool life when used with handheld tools of low rigidity, leading to polygonal hole cross-sections due to vibration and deflection.
Innovation Solution
A drill design featuring first and second cutting edges with continuously or intermittently decreasing point and relief angles, and a deflection reducer to minimize vibration and improve hole quality, suitable for both high-rigidity 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 quality and tool life are improved when using high-rigidity spindles, but vibration increases and hole quality deteriorates when using low-rigidity handheld tools
Solution Approach 1:
The drill is divided into two distinct cutting edge groups: first cutting edges at the tip with continuously decreasing point and relief angles for drilling, and second cutting edges at the rear end with constant point angle and relief angle for finishing. This segmentation allows each group to have optimized geometry for its specific function, reducing overall vibration while maintaining hole quality.
Solution Approach 2:
Different portions of the drill have different geometric characteristics: the tip portion has continuously varying angles suitable for drilling, while the rear end portion has constant angles suitable for finishing. This local quality differentiation optimizes performance for each specific operation and reduces vibration in low-rigidity applications.
2Productivity
If the point angle continuously decreases from tip to rear end, then cutting performance is improved, but the structure becomes more complex and difficult to manufacture
Solution Approach 1:
The cutting edges are segmented into two groups with different geometric progression patterns. The first cutting edges have continuously decreasing angles while the second cutting edges have constant angles, simplifying the manufacturing process compared to a fully continuous variation while maintaining cutting performance.
Solution Approach 2:
The drill geometry is optimized locally: continuously varying angles at the tip for effective drilling, and constant angles at the rear end for easier manufacturing and consistent finishing performance. This local optimization balances manufacturing ease with cutting effectiveness.
Data Source
AI summary
According to one implementation, 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 by being inserted into the prepared hole. The deflection reducer is formed between the first cutting edges and the second cutting edges.