Drill Bit Web Thickness and Helix Angle Optimization
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Solution Overview
Problem
Conventional drill bits with chisel edges often fail to provide accurately located and round holes, as they tend to deviate from the desired center location and produce out-of-round holes due to the transmission of tool holder imperfections, and deeper flutes for debris removal compromise the strength of the drill bit.
Innovation Solution
A drill bit design featuring a thinner web thickness at the tip, a smaller helix angle of 30° to 35°, and a bi-metal construction with a hardened cutting portion and a tougher shank, which includes a pilot tip with a split point cutting edge arrangement and deeper flutes for efficient debris removal without compromising strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deeper flutes are used for debris removal, then debris removal efficiency is improved, but the web thickness is reduced which compromises the strength of the drill bit
Solution Approach 1:
The patent applies local quality by varying the web thickness along the length of the drill bit. The web is thicker at the shank and cutting portion to maintain strength, while being thinner in the flute region to enable deeper flutes for improved debris removal. This spatial variation in web thickness allows simultaneous optimization of both structural strength and debris removal efficiency.
2Ease of operation
If a chisel edge is used at the working end, then the drill bit can engage and move into the workpiece material, but the hole center location accuracy is poor and holes become out of round
Solution Approach 1:
The patent applies preliminary action by providing a pilot tip that extends axially ahead of the outer cutting portion. The pilot tip first engages the workpiece and creates a pilot hole that self-centers the drill bit, eliminating runout issues. This preliminary action ensures accurate hole center location before the main cutting edges engage the material.
Solution Approach 2:
The patent applies segmentation by dividing the cutting structure into distinct functional portions: a pilot tip with split point cutting edge for self-centering, and an outer cutting portion with major cutting edges for material removal. This segmentation allows each portion to perform its specific function optimally, with the pilot tip ensuring accuracy and the outer cutting portion ensuring ease of operation.
3Duration of action of moving object
If web thickness is reduced at the tip, then drilling life is enhanced, but the structural robustness may be compromised
Solution Approach 1:
The patent applies local quality by strategically locating the reduced web thickness at the tip region while maintaining adequate web thickness at the shank and cutting portions. This localized thinning extends drilling life by reducing friction and heat generation at the critical tip area, while the thicker web at other locations preserves overall structural robustness.
Data Source
AI summary
An elongated drill bit has a shank at one end and working end at the other. A flute portion is between the working end and the shank. The flute portion is continuous with the shank and working end and is generally unitarily formed with them. The flute portion has at least one flute with a helix angle between approximately 30° and 35°. The working end has a pilot tip with a cutting portion. A tapered web is formed in the flute portion, a thickness of the web at the tip of the working end is about 9% to 15% of the nominal diameter.