Step Drill Bit with Varying Helix and Rake Angles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Step drill bits used with impact drivers are prone to chipping due to the cutting edge being more susceptible to wear and damage, especially when drilling through thin-walled workpieces.
Innovation Solution
The design incorporates a shank with axially stacked, progressively sized steps and a flute that extends from the distal end to the proximal end, featuring cutting edges with varying helix and rake angles, where the helix angle at the terminal step increases by at least 70% and the rake angle increases by at least 40% relative to the first step, along with a specific ratio of helix to rake angles, and a protective coating for enhanced wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a step drill bit is used with an impact driver, then drilling capability is improved, but the cutting edge becomes more prone to chipping
Solution Approach 1:
The patent applies different helix angles and rake angles to cutting edges at different steps of the drill bit. Specifically, the helix angle increases from the first step to the terminal step, and the rake angle is optimized at each step to prevent chipping while maintaining drilling efficiency. This local differentiation of geometric parameters allows each cutting edge to be optimized for its specific function and position.
Solution Approach 2:
The patent systematically changes the helix angle and rake angle parameters across different steps of the drill bit. The helix angle increases progressively from the first step to the terminal step, while the rake angle is adjusted to maintain an optimal ratio. These parameter changes enable the cutting edges to withstand impact forces while maintaining cutting effectiveness.
2Productivity
If the helix angle is increased to improve chip evacuation, then drilling speed is improved, but cutting edge stability decreases
Solution Approach 1:
The patent optimizes the helix angle parameter at each step to balance chip evacuation and cutting edge stability. The helix angle increases from the first step to the terminal step, improving chip evacuation and drilling speed, while the rake angle is simultaneously adjusted to maintain structural stability and prevent chipping.
Solution Approach 2:
Different helix angles are applied to different steps of the drill bit based on their specific requirements. The terminal step has a larger helix angle for efficient chip evacuation in larger holes, while smaller steps have smaller helix angles to maintain stability during initial drilling.
3Productivity
If the rake angle is increased to reduce cutting forces, then drilling efficiency is improved, but edge strength decreases
Solution Approach 1:
The patent optimizes the rake angle parameter at each step to balance cutting efficiency and edge strength. The rake angle is increased to reduce cutting forces and improve drilling efficiency, while the helix angle is simultaneously adjusted to maintain edge strength and prevent chipping, particularly at the terminal step.
Data Source
AI summary
A step drill bit includes a shank and a body that defines a plurality of axially stacked, progressively sized steps including a first step, a terminal step, and a plurality of intermediate steps having incrementally increasing diameters disposed between the first and terminal steps. The step drill bit includes a flute in the body extending from the distal end to the proximal end and a plurality of cutting edges formed in the body. Each cutting edge is disposed along one of the plurality of steps. Each cutting edge defines a helix angle and a radial rake angle. The helix angle of the cutting edge at a first intermediate step of the plurality of intermediate steps is greater than the helix angle at the first step. The radial rake angle of the cutting edge at the first intermediate step is greater than the radial rake angle at the first step.