Segmented Drill Geometry for Low-Deflection Hole Reaming
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Solution Overview
Problem
Conventional drills with continuously changing point and relief angles struggle to maintain high accuracy when used with handheld tools, leading to suboptimal hole quality due to vibration and reduced spindle rigidity, especially when drilling composite materials or metals.
Innovation Solution
A drill design featuring first cutting edges with continuously decreasing point and relief angles, accompanied by a deflection reducer, which includes reamer cutting edges and a holding part to reduce deflection and improve hole quality across various drilling conditions.
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 accuracy deteriorates when used with handheld tools of low rigidity
Solution Approach 1:
The drill is divided into two distinct cutting edge portions: a first cutting edge portion with continuously changing point angle and relief angle for high-quality hole machining, and a second cutting edge portion with constant point angle and relief angle for stable drilling with handheld tools. This segmentation allows each portion to optimize for its specific function, resolving the contradiction between hole quality and stability.
Solution Approach 2:
Different portions of the cutting edges are given different geometric properties: the first portion (near the tip) has continuously varying angles for superior surface quality, while the second portion (farther from tip) has constant angles for vibration reduction. This local differentiation enables the drill to achieve both high hole quality and stable operation with low-rigidity handheld tools.
2Productivity
If the number of cutting edges is increased to three or more, then productivity is improved, but hole shape becomes polygonal due to increased vibration with handheld tools
Solution Approach 1:
The cutting edges are segmented into two functional groups: those with continuously changing angles that contribute to clean cutting and hole quality, and those with constant angles that provide structural stability and reduce vibration. This allows multi-edge drills to maintain both productivity and hole circularity.
Solution Approach 2:
The point angle and relief angle parameters are changed along the length of the cutting edges - starting with larger values at the tip for effective cutting, then transitioning to smaller constant values for vibration reduction. This parameter variation enables multi-edge drills to achieve both high productivity and circular hole shapes.
3Ease of operation
If a simple drill press with low spindle rigidity is used, then ease of operation is improved, but hole machining quality deteriorates due to drill deflection
Solution Approach 1:
The drill geometry is optimized locally: the tip portion has aggressive angles for clean cutting, while the rear portion has conservative constant angles for deflection reduction. This allows the drill to perform well even in low-rigidity setups while maintaining hole quality.
Solution Approach 2:
Instead of requiring high spindle rigidity to achieve good hole quality, the invention inverts the approach by designing the cutting edges themselves to provide inherent stability through the constant angle portion, enabling high-quality drilling with simple, low-rigidity equipment.
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 ream 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.