Chamfered Drill Corner Geometry for Chipping-Resistant Hole Making
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Solution Overview
Problem
Drills used for machining heat-resistant superalloys suffer from inferior tool life and quality issues due to edge chipping, particularly in the outer corner region, leading to unpredictable performance and reduced structural integrity.
Innovation Solution
A drill design featuring a chamfered corner and a rake reduced region with specific angle modifications, including a chamfer angle between 5° and 25° smaller than half the drill point angle and a reduced radial rake angle between 20° and 45° smaller than adjacent regions, enhances chipping resistance and tool life while maintaining hole quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If corner modifications and edge preparations are introduced to strengthen high stress areas, then tool life is improved, but hole quality deteriorates
Solution Approach 1:
The drill applies different geometric properties to different regions: the radially outermost portion has a chamfered clearance face with reduced radial rake angle to strengthen the corner, while the adjacent region maintains normal geometry for high-quality cutting. This local differentiation allows corner strengthening without compromising overall hole quality.
Solution Approach 2:
The invention changes geometric parameters locally at the corner region by reducing the radial rake angle by 20°-45° and applying a chamfer angle 5°-25° smaller than half the drill point angle. These parameter modifications strengthen the corner while the rest of the drill maintains optimal cutting geometry.
2Manufacturing precision
If a standard drill design is used, then hole quality can be maintained, but tool life becomes inferior and unpredictable due to edge chipping
Solution Approach 1:
The drill applies different geometric properties to different regions: the radially outermost portion has a chamfered clearance face with reduced radial rake angle to strengthen the corner, while the adjacent region maintains normal geometry for high-quality cutting. This local differentiation allows corner strengthening without compromising overall hole quality.
Solution Approach 2:
The chamfered portion and reduced rake angle region are built into the drill geometry before machining begins. This preliminary structural reinforcement prevents edge chipping from occurring in the first place, rather than attempting to correct it during or after the machining process.
3Strength
If the radial rake angle is reduced significantly at the outermost portion, then chipping resistance improves, but cutting performance may be impaired
Solution Approach 1:
The drill applies different geometric properties to different regions: the radially outermost portion has a chamfered clearance face with reduced radial rake angle to strengthen the corner, while the adjacent region maintains normal geometry for high-quality cutting. This local differentiation allows corner strengthening without compromising overall hole quality.
Solution Approach 2:
The invention applies an aggressive rake correction (20°-45° reduction) specifically at the critical corner region where chipping occurs, rather than uniformly across the entire cutting edge. This partial application of extreme geometry modification targets the problem area without unnecessarily compromising overall cutting performance.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Drill (1), comprising - a front end (2) including a drill point (3) having an obtuse drill point angle (θ); - a rear end (4); - a centre axis (C) extending from the front end (2) to the rear end (3); and - a peripheral surface (5) connecting the front end and the rear end, wherein at least two chip flutes (6) are formed in the peripheral surface (5), each chip flute (6) extending helicoidally around the centre axis (C) from the front end (2) towards the rear end (4). For each of the chip flutes (6), a cutting edge (7) is formed at an intersection between a rake face (8) in the chip flute (6) and a clearance face (9) at the front end (2) of the drill. A radially outermost portion of the clearance face (9) adjacent the cutting edge (7) is a chamfered portion (91), wherein the part of the cutting edge (7) bordering the chamfered portion (91), when seen in a side view of the drill from a direction perpendicular to a plane containing the centre axis and the radially outermost point of the cutting edge, extends with respect to the centre axis (C) at a chamfer angle (α) that is between 5° and 25° smaller than half the drill point angle (θ). Moreover, a radially outermost portion of the rake face (8) is a rake reduced region (81) in which a reduced radial rake angle (γ2) is between 20° and 45° smaller than a preceding radial rake angle (γ1) in an adjacent region of the rake face (8) adjoining the rake reduced region (81) in a direction towards the centre axis (C).