Spot Drilling Insert With Offset Land Curvature
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Solution Overview
Problem
Existing spot drilling tools with point angles greater than 100° lack sufficient centering and guidance for very small diameter drills, and as the point angle is reduced to provide steeper tapered spots, the cutting edges become weakened, making them less durable for micro-drilling operations.
Innovation Solution
A spot drilling insert with a point angle of approximately 60°, featuring diametrically opposed cutting edges, conical land surfaces with an offset axis of curvature, and angled linear flutes that converge towards the tip, providing enhanced relief clearance and robust cutting edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the point angle of the spot drilling tool is reduced to provide a steeper tapered spot for better centering and guidance, then the centering and guidance capability is improved, but the cutting edges become weakened and durability decreases
Solution Approach 1:
The patent changes the geometric parameters of the spot drilling tool by reducing the point angle to approximately 60° (from the conventional 118°), creating a steeper tapered spot that provides superior centering and guidance for micro-drills while maintaining cutting edge durability through optimized flute geometry and relief clearance design
Solution Approach 2:
The patent applies different geometric characteristics to different parts of the cutting tool: the point angle is reduced to 60° for better centering, while the flutes are designed with specific angles and the relief clearance is optimized to maintain cutting edge strength, allowing each region of the tool to have the quality needed for its specific function
2Manufacturing precision
If the point angle is reduced below 90° to provide adequate centering for very small diameter drills, then the pilot hole accuracy is improved, but the relief angle required increases and cutting edges become too weak
Solution Approach 1:
The patent reduces the point angle to approximately 60° to provide the steep taper needed for accurate pilot hole formation in micro-drilling, while simultaneously optimizing other parameters including flute angle, relief clearance, and land surface geometry to maintain sufficient cutting edge strength despite the reduced point angle
Solution Approach 2:
The patent addresses the strength issue by introducing conical land surfaces with an offset axis of curvature, adding a dimensional element that provides the necessary relief clearance and structural support to the cutting edges, allowing the tool to maintain strength while having a reduced point angle
3Ease of manufacture
If a twist drill is used for spot drilling, then the tool can be sharpened and reused, but removing and re-calibrating the drill is time-consuming
Solution Approach 1:
The patent segments the drilling tool into two parts: a reusable tool holder that remains in the machine and a replaceable insert containing the cutting edges. This allows the cutting insert to be quickly changed without removing and re-calibrating the entire drill, reducing machine downtime while maintaining the ability to renew cutting edges
Solution Approach 2:
The patent employs a disposable or replaceable cutting insert that can be quickly exchanged when worn, rather than sharpening and reusing the entire drill. The insert is designed to be replaced in minutes without calibration, making it more time-efficient despite the additional component
4Productivity
If a spade drill with replaceable insert is used, then machine downtime is reduced and calibration is minimized, but the point angle is typically excessive for very small diameter drills
Solution Approach 1:
The patent changes the point angle parameter from the conventional 118° (twist drill) or excessive angle (spade drill) to approximately 60°, creating a steeper taper that provides superior centering and guidance for very small diameter drills while maintaining the productivity benefits of a replaceable insert design
Data Source
AI summary
A spot drilling tool includes a drill holder and an insert removably mounted to the holder. The insert is a standardized part configured to support a drill point in a predetermined position forward of the drill holder and centered on the rotational axis of the drill holder. The drill point has two flutes and two substantially conical land surfaces extending between the flutes. The land surfaces have centers of curvature offset from the rotational axis of the insert to provide radial clearance for the trailing portion of the land. A chisel edge at the tip of the drill point is supported by a tapered web defined between the diagonally opposed and offset flutes. Linear cutting edges are formed at the junction of a planar flute surface and the conical land surface. The cutting edges define a narrow included point angle of between 50° and 80°.