Indexable Drill Body Chip Discharge Groove Surface Roughness
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Solution Overview
Problem
Existing indexable drills face challenges in maintaining efficient chip discharging and longevity due to increased friction and wear in the chip discharging groove surfaces, as well as vulnerability of thinned wall portions to breaking under excessive cutting forces.
Innovation Solution
The design includes a drill body with a chip discharging groove featuring a smoothed surface with a roughness of at most 0.5 μm, a central edge and outer peripheral edge attachment seat, and a rounded crossing portion between the first and second wall surfaces, made from materials like carbon steel or tool steel with a hardness of 40-60 HRC, and optionally coated with hard chrome plating to enhance wear resistance and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple rows of grooves are formed in the chip discharging groove wall surface, then chip discharge efficiency is improved, but friction between the grooves and chips increases causing rapid wear
Solution Approach 1:
The groove surfaces are subjected to shot blasting treatment before final machining, which introduces compressive residual stress and increases surface hardness. This preliminary hardening action prevents rapid wear during subsequent chip discharge operations, allowing the grooves to maintain their chip-discharge function over extended periods.
Solution Approach 2:
The surface roughness of the groove walls is precisely controlled within the range of 0.1 to 1.0 μm Ra through shot blasting and finishing operations. This optimized roughness parameter reduces friction between chips and groove surfaces while maintaining effective chip discharge, thereby extending the service life of the grooves.
2Ease of manufacture
If thinned wall portions are formed at insert attachment seats, then insert installation is facilitated, but the thinned portions are vulnerable to breaking under cutting forces
Solution Approach 1:
The thinned wall portions at the insert attachment seats are subjected to shot blasting treatment before final machining and assembly. This preliminary action creates a hardened surface layer with compressive residual stress, significantly increasing the strength and fracture resistance of these vulnerable areas while maintaining their thin-walled structure for easy insert installation.
Solution Approach 2:
Shot blasting treatment is applied selectively to the thinned wall portions at the insert attachment seats, creating localized hardening only where needed. This local quality enhancement strengthens the vulnerable areas without affecting other parts of the drill body, maintaining both ease of insert installation and structural integrity.
3Duration of action of moving object
If groove surfaces are hardened to reduce wear, then service life is extended, but chip discharge smoothness may be compromised
Solution Approach 1:
The surface roughness is precisely controlled within the range of 0.1 to 1.0 μm Ra through shot blasting followed by finishing operations. This optimized roughness parameter achieves a balance: it is rough enough to provide mechanical interlocking and chip discharge propulsion, yet smooth enough to minimize friction and ensure chips move through the grooves without excessive resistance or adhesion.
Solution Approach 2:
The shot blasting process, which could be considered harmful due to surface roughening, is actually beneficial as it creates compressive residual stress and increases surface hardness. The controlled roughness introduced (0.1-1.0 μm Ra) then serves to improve chip discharge by providing mechanical interlocking, converting what might be seen as a surface defect into a functional advantage.
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
This solution effectively reduces chip adhesion and wear on the groove surfaces, ensuring smooth chip discharge and preventing the thinned wall portions from breaking, thereby improving chip discharging efficiency and extending the drill's lifespan.
Implementation Method 1
a wall surface defining the chip discharging groove at least partly comprises a smoothed surface with a surface roughness of at most 0.5 μm (JIS•B0601:2001) in terms of arithmetic average roughness Ra
Implementation Method 2
optionally coated with hard chrome plating to enhance wear resistance and strength
Data Source
AI summary
An indexable drill includes an insert attachment seat and a chip discharging groove formed so as to extend from a leading end surface to a trailing end side of the drill in the direction of the axis of rotation and through which chips generated by the cutting insert are discharged, and in that a wall surface defining the chip discharging groove at least partly includes a smoothed surface with a surface roughness of at most 0.5 μm in terms of arithmetic average roughness Ra, the wall surface of the chip discharging groove is partly formed on a thinned wall portion thinned by the central edge attachment seat and the outer peripheral edge attachment seat, and a crossing portion between the first wall surface and the second wall surface in the thinned wall portion is rounded.