Two-Stage Drill Geometry for Circular Holes Under Low Rigidity
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Solution Overview
Problem
Conventional drills, such as the R-drill, struggle to maintain high accuracy and quality when drilling composite materials or metals using handheld tools with low rigidity or accuracy, often resulting in polygonal hole cross-sections due to vibration.
Innovation Solution
A drill design featuring at least one first cutting edge with a continuously or intermittently decreasing point and relief angle, paired with a second cutting edge and a deflection reducer, which reduces deflection of the second cutting edge and allows for high-quality drilling regardless of the spindle rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional drill (R-drill) with continuously varying point angle and relief angle is used, then high drilling quality and extended tool life are achieved when using machine tools with high spindle rigidity, but vibration increases and hole shape deteriorates to polygonal when using handheld tools with low spindle rigidity
Solution Approach 1:
The drill is divided into two distinct cutting edge groups: first cutting edges for drilling and second cutting edges for finishing. This segmentation allows each group to perform its specific function optimally, with the first cutting edges creating the initial hole and the second cutting edges refining it to circular shape, thereby reducing vibration and improving hole quality when using handheld tools
Solution Approach 2:
The second cutting edges act as an intermediary element that refines the hole shape after the first cutting edges have drilled it. This intermediary finishing action corrects the polygonal shape caused by vibration during drilling, ensuring a circular hole cross-section is achieved even when using handheld tools with low spindle rigidity
2Productivity
If the point angle continuously decreases from tip to rear end, then cutting performance is optimized, but production complexity increases due to curved profile requirements
Solution Approach 1:
The continuous variation of point angle is segmented into discrete steps between the first and second cutting edges. This allows the drill to achieve optimized cutting performance through controlled angle variations while simplifying manufacturing, as the angles can be set at specific positions rather than requiring continuous curved profiles
Solution Approach 2:
Different point angles are applied locally to different cutting edge groups. The first cutting edges have point angles optimized for drilling, while the second cutting edges have point angles optimized for finishing. This local differentiation achieves optimal cutting performance for each function while simplifying production compared to continuous variation
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. The deflection reducer is formed between the first cutting edges and the second cutting edges. The deflection reducer is inserted into the prepared hole.