Drill Oil Hole Geometry for Coolant Flow and Tool Rigidity
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Solution Overview
Problem
Drills with round cutting oil supply holes face challenges in achieving sufficient cutting oil discharge and tool rigidity, especially in high-feed processing and when dealing with thick or hard materials, leading to potential tool instability due to stress concentration near the cutting oil supply hole.
Innovation Solution
A drill design featuring a bar-shaped tool with a helical discharge flute, a cutting edge, and an oil hole with a fan-shaped cross-section, where the rear-side inner wall surface is curved in a circular arc shape, increasing the discharge amount of cutting oil and securing tool rigidity by maintaining a wide distance between the ridge section and the oil hole, while the gash portion's ridge line extends in a circular arc shape to enhance chip curling and discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cutting oil supply hole is positioned near the R portion to improve cutting oil delivery, then the lubricating performance and cooling performance are improved, but stress concentration occurs at the section with short distance between the R portion and the cutting oil supply hole
Solution Approach 1:
The rearward-side inner wall surface is designed to curve in a circular arc shape toward the forward side in the rotation direction, creating a smooth transition that eliminates stress concentration points while maintaining adequate distance between the R portion and cutting oil supply hole
Solution Approach 2:
The circular arc-shaped rearward-side inner wall surface is specifically positioned to address the stress concentration issue in the critical region between the R portion and cutting oil supply hole, while other portions of the drill maintain their original design characteristics
2Quantity of substance
If the cross-sectional area of the cutting oil supply hole is increased to improve discharge amount, then the lubricating performance and cooling performance are improved, but tool rigidity deteriorates
Solution Approach 1:
The circular arc-shaped rearward-side inner wall surface enables optimal positioning of the cutting oil supply hole that maintains adequate distance from the R portion, allowing for larger cross-sectional area without compromising tool rigidity
Solution Approach 2:
The cutting oil supply hole is given a fan-shaped cross-section with specific dimensional relationships (outer-circumference-side radius larger than inner-circumference-side radius) that maximize discharge area while controlling stress distribution
Data Source
AI summary
A drill is provided with a flank at a leading end portion of a body. An oil hole is provided at the flank, having a fan-shaped cross-section. The fan-shaped cross-section is formed by being surrounded by a front-side inner wall surface, a rear-side inner wall surface, an outer peripheral-side inner wall surface, and an inner peripheral-side inner wall surface. Compared to a round hole, a discharge performance of cutting fluid of the oil hole is high. The rear-side inner wall surface curves in a circular arc shape toward the front in a rotation direction. Thus, the drill can secure a distance between a ridge section of the flank and the rear-side inner wall surface to be wide, can suppress stress acting on a section between the ridge section of the flank and the oil hole, and can thus increase a discharge amount of the cutting fluid and also secure a tool rigidity.