Multi-Edge Drill With Pilot Shaft For Deep Hole Accuracy
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Solution Overview
Problem
Conventional two-edge stepped double margin drills experience high cutting resistance, leading to increased abrasion, reduced tool life, and decreased precision when drilling deep holes in high-hardness materials like aluminum alloys, due to their limited cutting edges and twisted grooves that can cause deformation and chip accumulation.
Innovation Solution
A drill with a shank and body featuring a pilot shaft portion, odd-numbered twisted grooves, and multiple cutting edges, which reduces the number of drilling steps required to achieve a desired hole diameter while maintaining high accuracy and rigidity, and includes auxiliary cutting edges for improved chip evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-edge stepped double margin drill is used, then the inner peripheral surface smoothness is improved and hole processing accuracy is improved, but the cutting resistance is large and the number of drilling performances required increases
Solution Approach 1:
The drill is divided into multiple cutting edges (three or more) instead of two, with each edge contributing to material removal. The cutting edges are arranged at specific angles (e.g., 120 degrees apart for three edges) to distribute cutting forces and improve efficiency while maintaining precision through the stepped structure.
Solution Approach 2:
The number of cutting edges is changed from two to three or more, fundamentally altering the cutting mechanism. This parameter change reduces the number of drilling passes required while the stepped geometry parameters are optimized to maintain surface smoothness and hole accuracy.
2Object-generated harmful factors
If the twisted grooves are made deep for chip evacuation, then the chip evacuation capacity is improved, but the web thickness is decreased and drill rigidity is lowered
Solution Approach 1:
The drill features varying groove depths at different locations - deeper grooves near the cutting edges for effective chip evacuation, and shallower or no grooves in the web area to maintain rigidity. This local differentiation allows simultaneous optimization of chip flow and structural strength.
Solution Approach 2:
The twisted grooves are designed with three-dimensional helical paths that evacuate chips along the axial and radial directions simultaneously. This multi-directional chip evacuation reduces the need for excessive groove depth while maintaining effective chip removal capability.
3Productivity
If a three-edge drill is used, then the cutting resistance is reduced and tool life is improved, but the chisel portion area is greater and positioning precision is lowered
Solution Approach 1:
A pilot hole or guide hole is drilled first to establish the precise hole location before the main three-edge drill performs the final drilling operation. This preliminary positioning action eliminates the positioning inaccuracy inherent in three-edge drills while maintaining their cutting efficiency advantages.
Solution Approach 2:
The pilot hole acts as an intermediary element that transfers the positioning function from the main drill to a separate guiding operation. This mediator allows the three-edge drill to focus on its strength (cutting efficiency) while the pilot hole handles positioning precision.
4Manufacturing precision
If the cutting margin is set small to eliminate cutting distortion, then the hole diameter accuracy is improved, but the number of drilling performances increases and productivity decreases
Solution Approach 1:
The total cutting margin is segmented across three or more cutting edges, with each edge removing a smaller portion of material. This distribution allows the drill to achieve the desired hole diameter in fewer passes while maintaining accuracy through the cumulative effect of multiple precise cutting edges.
Data Source
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AI summary
A drill includes a body 20 and a pilot shaft portion 30 that projects from a distal end portion of the body 20 and has a smaller diameter than the body 20 and the pilot shaft portion 30 and the body 20 are concentric. The pilot shaft portion 30 includes a shaft main body portion 31, a distal end flat surface 32 that is at a distal end of the shaft main body portion 31, and a distal end tapered surface 23 that is between an outer peripheral surface of the shaft main body portion 31 and the distal end flat surface 32 and has a certain distal end angle β. The body 20 includes an odd number of twisted grooves 22 on an outer peripheral surface thereof and three main cutting edges 23 on a distal end tapered surface 25. The distal end tapered surface 25 ranges from the outer peripheral surface of the body 20 to the pilot shaft portion 30 and has a certain distal end angle α. The pilot shaft portion 30 includes auxiliary twisted grooves 24 continuous from the respective twisted grooves 22 and auxiliary cutting edges 34. The auxiliary twisted grooves 24 extend from the outer peripheral surface of the shaft main body portion 31 to the respective distal end tapered surfaces 33. The auxiliary cutting edges 34 are formed on the respective distal end tapered surfaces 34. According to the drill and the method of forming a hole in overlapped plates, a hole can be formed in overlapped plates or a thick material and the number of process steps until obtaining a desired hole diameter is reduced and tool life is long and processing accuracy is high.