Deep-hole-boring Drill Head Guide Pad Geometry for Wear Balance
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Solution Overview
Problem
Deep hole boring drill heads face challenges in maintaining balance between cutting blades and guide pads due to thermal strain and wear, leading to spiral marks on the inner peripheral surface of holes, which are critical for high-reliability applications like atomic power plant tube seats.
Innovation Solution
The drill head design incorporates a flat land on the leading end peripheral edge of the cutting blade and a concavo-convex shape with specific moving radii for the guide pads, reducing the force required for burnishing and enhancing durability, thereby maintaining balance between the cutting blade and guide pad for a longer period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the aspect ratio L/D of the hole increases, then the drilling depth is improved, but unstable vibration of the boring bar occurs causing spiral marks
Solution Approach 1:
The drill head is segmented into multiple functional components: cutting blades for material removal, guide pads for stabilization, and burnishing pads for surface finishing. This segmentation allows each component to perform its specific function optimally, with guide pads preventing boring bar vibration and maintaining surface quality during deep hole drilling
Solution Approach 2:
Different portions of the drill head have specialized local properties: cutting blades have sharp edges for cutting, guide pads have specific hardness and geometry for stabilization, and burnishing pads have smooth surfaces for finishing. The guide pads are positioned at specific locations to provide localized support and prevent vibration at critical points
2Power
If the cutting blade receives the largest resistance from the work, then the cutting performance is improved, but the wear rate of the cutting blade increases reducing durability
Solution Approach 1:
The cutting blade geometry is optimized with specific parameters including a flat land at the leading end peripheral edge to prevent diameter reduction from wear, and a back taper on the rear surface to control chip flow and reduce wear. The guide pad moving radius is set to 0.95-1.05 times the cutting blade moving radius to maintain proper contact force and distribute wear evenly
3Manufacturing precision
If the balance between cutting blade and guide pad is maintained, then the spiral mark generation is prevented, but thermal strain from brazing and welding processes makes accuracy management difficult
Solution Approach 1:
The cutting blade and guide pad are pre-assembled onto the boring bar with predetermined positions and orientations before final installation. The guide pad moving radius is calculated in advance as 0.95-1.05 times the cutting blade moving radius to ensure proper balance and contact force, reducing the need for complex post-assembly adjustments
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 design effectively prevents spiral marks, ensuring high throughput and extended usage of the drill head by reducing wear on the guide pads and maintaining stability during the boring process.
Implementation Method 1
the rate of progression of the wear of the cutting blade, which receives the largest resistance from the work, is high, that is, durability of the cutting blade is lower than that of the guide pad
Implementation Method 2
a concavo-convex shape with specific moving radii for the guide pads, reducing the force required for burnishing
Implementation Method 3
A manufacturing process of the deep hole boring drill head includes a brazing process of a cutting blade and a welding process of a head shank and a thread shank. Therefore, thermal strain tends to occur
Implementation Method 4
A manufacturing process of the deep hole boring drill head includes a brazing process of a cutting blade and a welding process of a head shank and a thread shank. Therefore, thermal strain tends to occur
Implementation Method 5
when the boring progresses, the cutting blade and the guide pad are worn away, and a balance therebetween is broken
Data Source
Figure 1(A)~2(B)
Figure 3~4
Figure 5~6
AI summary
In order to increase the durability of a deep-hole drill head, wherein a cutting blade and a guide pad are brazed to a head body, and to prevent generation of spiral marks even after long-term use, disclosed is a deep-hole-boring drill head (1)-which is provided with a head body (3), a cutting blade (11), a first guide pad (21), and a second guide pad (23)-wherein a flat land is provided to the peripheral edge (16) of the end of the cutting blade (11), a first moving radius (a) from the rotational center (P) of the head body (3) to the peripheral edge (16) of the end of the cutting blade (11) and a third moving radius (c) from said rotational center (P) to the primary guide surface (24) of the second guide pad (23) are equal, and a second moving radius (d) from the rotational center (P) of the head body (3) to the primary guide surface (22) of the first guide pad (21) is smaller than the first moving radius (a). The guide pads are, in the primary guide surfaces thereof, provided with a first region having a first radius that is the same length as the radius of the inner peripheral surface of the hole, and a second region having a moving radius that is smaller than said first radius, and the first region widens in the direction towards the back end from the leading edge of the primary guide surface.