Drill Coolant Hole Geometry for Flow and Crack Resistance
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Solution Overview
Problem
Existing rotating tools with coolant holes suffer from stress concentration at corner portions, insufficient coolant discharge flow rate, impaired chip discharge performance, and potential chip clogging due to convexly curved inner wall faces and small cutting edge diameters.
Innovation Solution
A rotating tool design featuring a coolant hole with a first concavely curved portion on the inner peripheral side and a second concavely curved portion on the outer peripheral side, along with third concavely curved portions and linear portions, which together increase the coolant hole's cross-sectional area and prevent stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the coolant hole is designed with convexly curved inner wall faces to reduce stress concentration, then the tool life is extended, but the cross-sectional area of the coolant hole decreases and coolant discharge flow rate becomes insufficient
Solution Approach 1:
The patent inverts the conventional convexly curved inner wall face design to a concavely curved inner wall face design. This inversion increases the cross-sectional area of the coolant hole, allowing sufficient coolant discharge flow rate while the outer wall face maintains convex curvature to prevent stress concentration and extend tool life.
Solution Approach 2:
The patent applies different curvature characteristics to different parts of the coolant hole: the inner wall face has concave curvature to maximize cross-sectional area and coolant flow, while the outer wall face has convex curvature to reduce stress concentration. This local differentiation resolves the contradiction between coolant flow rate and tool life.
2Strength
If the inner peripheral side inner wall face is designed with convex curve to increase structural strength, then the tool durability improves, but sufficient coolant cannot be supplied to the inner peripheral side and chip discharge performance is impaired
Solution Approach 1:
The patent inverts the convex curve design on the inner peripheral side to a concave curve design. This increases the cross-sectional area available for coolant flow to the inner peripheral side and improves chip discharge performance, while the outer wall face maintains convex curvature for structural strength.
Solution Approach 2:
The patent applies concave curvature to the inner peripheral side inner wall face to enhance coolant supply and chip discharge, while applying convex curvature to the outer wall face for structural strength. This local differentiation resolves the contradiction between strength and productivity.
3Temperature
If the coolant hole cross-sectional area is increased to improve coolant discharge flow rate, then the cooling efficiency improves, but stress concentration at corner portions increases and cracks are likely to occur
Solution Approach 1:
The patent inverts the inner wall face curvature from convex to concave to increase cross-sectional area and improve cooling efficiency, while the outer wall face maintains convex curvature to prevent stress concentration and crack formation.
Solution Approach 2:
The patent applies concave curvature to the inner wall face to maximize cross-sectional area for cooling, while applying convex curvature to the outer wall face to prevent stress concentration. This local differentiation resolves the contradiction between cooling efficiency and crack resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances coolant discharge flow rate, prevents chip clogging, and extends tool life by ensuring effective cooling and lubrication of the cutting edge, while also preventing crack generation due to reduced stress concentration.
Implementation Method 1
a coolant hole that extends toward a front side in an axis direction in the rotating tool main body opens to at least one of the tip flank face and the inner wall face of the chip discharge flute
Implementation Method 2
the coolant hole is provided with a first concavely curved portion located on an inner peripheral side of the rotating tool main body and formed in a concavely curved shape recessed to the inner peripheral side, a second concavely curved portion located on an outer peripheral side of the rotating tool main body
Implementation Method 3
the curvature radius of the concave curve at this corner portion cannot be increased, and stress is concentrated and a crack is likely to be generated at the stage of material molding
Data Source
AI summary
In a rotating tool with a coolant hole, a coolant hole extending to a front side in the direction of an axis opening to a tip flank face of a drill main body that is rotated around the axis. In a cross section orthogonal to the axis, the coolant hole is provided with a first concavely curved portion located on an inner peripheral side of the drill main body and formed in a concavely curved shape recessed to the inner peripheral side, a second concavely curved portion located on an outer peripheral side of the drill main body and formed in a concavely curved shape recessed to the outer peripheral side with a larger curvature radius than the first concavely curved portion, two third concavely curved portions having a center of a curvature radius located inside the coolant hole with a smaller curvature radius than the second concavely curved portion.