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Effect of Cutting Edge Preparation by Abrasive Brushing on End Mill Wear and Surface Quality of Aisi P20 Steel

This study demonstrates that optimizing pneumatic abrasive brushing parameters, particularly using silicon carbide micro-abrasives, effectively engineers precise cutting edge microgeometries on carbide end mills, resulting in a 21% increase in tool life and improved surface quality when milling AISI P20 steel.

Original authors: Wiliam Buckell, Luccas Augusto Pedrassani Delgado, Rodrigo Panosso Zeilmann

Published 2026-07-27

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Wiliam Buckell, Luccas Augusto Pedrassani Delgado, Rodrigo Panosso Zeilmann

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the world of manufacturing as a giant, high-stakes game of "cut and shape." In this arena, machines carve everything from car parts to the molds that make plastic toys. But there's a catch: the tools doing the cutting are made of incredibly hard materials, like cemented carbide, and they have to be razor-sharp to work. However, just like a kitchen knife that's been sharpened on a rough stone, these industrial tools often come out of the factory with tiny, invisible flaws—microscopic burrs, jagged edges, and uneven surfaces. Think of it like a brand-new sneaker that has a tiny, rough thread sticking out of the sole; it might not stop you from walking, but it will cause a blister if you run a marathon. In the world of metalworking, these tiny defects cause the tool to wear out faster, overheat, and leave the final product looking scratchy instead of smooth. Engineers have long searched for a way to "polish" these microscopic edges without ruining the tool's sharpness, hoping to make the tools last longer and the products look better.

This is where the story of a recent study from the University of Caxias do Sul comes in. The researchers decided to test a method called "abrasive brushing" to fix these tiny edge defects. Imagine taking a very stiff, high-speed brush—like a super-powered toothbrush, but with tiny grains of sand glued to the bristles—and gently running it over the cutting edge of a metal drill bit. The goal was to see if this brushing could smooth out the microscopic jaggedness, creating a perfect, rounded edge that would slide through metal more easily. They tested two different types of "sand" on the brush: one made of aluminum oxide and another made of silicon carbide. They played with different settings, like how fast the brush spun, how hard it pressed against the metal, and the angle at which it hit the edge. After finding the perfect "brushing recipe," they put the treated tools to the test, milling a tough type of steel (AISI P20) used for making molds, and compared them to untreated, "raw" tools.

The results were like finding the secret sauce for tool longevity. The researchers discovered that the way you brush the tool completely changes the shape of its edge. They found that the angle of the brush determined the shape of the curve, while how deep the brush pressed in determined the size of that curve. Interestingly, spinning the brush faster didn't always mean a better result; sometimes it just made the bristles flake off too quickly. The real winner was a specific combination using silicon carbide abrasives with a gentle touch and a specific angle. This "Configuration 15" created a beautiful, symmetrical, and smooth edge that was free of the tiny chips and cracks found on the untreated tools.

When they actually started cutting the steel, the difference was clear. The brushed tools didn't just look better; they performed better. While both tools started out wearing down at a similar pace, the untreated tool quickly started to struggle, developing more wear and tear. The brushed tool, however, held its ground. By the time the wear reached a critical limit of 0.2 mm, the brushed tool had managed to cut 23.88 meters of steel, while the untreated tool had to stop at just 19.68 meters. That's a 21% boost in life, essentially meaning the tool could do more work before needing to be replaced.

The study also looked at the surface quality of the steel being cut. Generally, the brushed tools left a smoother surface, with fewer scratches and a more consistent texture, especially as the tools got older and more worn. However, there was a tiny twist: for one specific measurement of the "tallest" peak on the surface (called Rz1max), the untreated tool actually performed slightly better. The researchers suggest this might be because the brushed tool's edge was so rounded that it sometimes "ploughed" or pushed the metal rather than slicing it cleanly, creating a tiny bump. But overall, the brushing process proved to be a highly effective, low-cost way to engineer better tools. It's a bit like giving a runner a pair of perfectly fitted, smooth-soled shoes instead of ones with a rough thread; the runner doesn't just finish the race faster, they finish with fewer blisters and a better time. The paper concludes that this simple brushing technique is a powerful tool for making manufacturing more efficient and reliable.

Technical Summary: Effect of Cutting Edge Preparation by Abrasive Brushing on End Mill Wear and Surface Quality of AISI P20 Steel

Problem Statement
In the manufacturing sector, particularly in mold and die production, the demand for higher productivity and stricter tolerances necessitates optimized machining processes. The cutting tool is a critical component, yet the grinding process used to manufacture end mills often leaves the cutting edge with defects such as burrs, micro-chipping, and irregularities. These manufacturing defects compromise the mechanical strength of the cutting wedge, leading to reduced tool life, unstable cutting conditions, and poor workpiece surface quality. While cutting edge preparation (CEP) is a known method to mitigate these issues, the specific influence of abrasive brushing parameters on the resulting microgeometry and subsequent machining performance requires further investigation to optimize the process for mold steels like AISI P20.

Methodology
The study employed a two-stage experimental approach to evaluate the efficacy of abrasive brushing on carbide end mills.

Prototype Brushing Tests: A series of tests were conducted on prototype end mills (8 mm diameter, 2 edges, 0° helix) to determine optimal brushing parameters. The process utilized a pneumatic rotary tool with abrasive discs made of non-woven nylon filaments impregnated with either Aluminum Oxide (Al2O3, 320 grit) or Silicon Carbide (SiC, 400 grit). Parameters varied included brush rotation speed (6,000–10,000 rpm), contact depth (1.0–3.5 mm), and disc inclination angle (0°–25°). Microgeometries were analyzed using Scanning Electron Microscopy (SEM) and contact profilometry to assess edge radius ( $r_\beta$ ), rounding shape, and the K-form factor.
Machining Tests: Based on the prototype results, the optimal configuration was applied to commercial 6 mm uncoated cemented carbide (K40 grade) end mills. These tools were used to machine AISI P20 steel (37 ± 1 HRC) under dry conditions with a cutting speed of 180 m/min, feed of 0.05 mm/tooth, and specific depths of cut. The performance of the brushed tools was compared against untreated (sharp) tools. Tool life was defined by a flank wear limit ( $VB_{MAX}$ ) of 0.2 mm or chipping exceeding this dimension. Surface quality was evaluated via roughness parameters ( $R_a$ , $R_z$ , $R_{z1max}$ ) and optical texture analysis at the beginning and end of the tool life.

Key Contributions and Results
The research established a direct correlation between brushing parameters and the resulting cutting edge microgeometry:

Parameter Influence: The brush angle dictated the symmetry of the rounding, while contact depth significantly influenced the size and profile of the rounding. Higher rotational speeds increased the material removal rate but required careful control to avoid filament damage.
Abrasive Performance: While both abrasives removed material, the Silicon Carbide (SiC) abrasive proved superior in generating defect-free geometries. The Al2O3 abrasive occasionally caused carbide grain detachment and surface imperfections.
Optimal Configuration: "Configuration 15" (SiC abrasive, 6,000 rpm, 15° inclination, 1.0 mm contact depth) yielded the most suitable microgeometry, characterized by a homogeneous surface, no chipping, and a shape factor ( $K$ ) of 0.98, indicating near-perfect symmetry.
Tool Life Improvement: In machining tests, the brushed tool demonstrated a 21.34% increase in tool life compared to the untreated tool, reaching 23.88 linear meters versus 19.68 meters before reaching the $VB_{MAX}$ criterion. The brushing process effectively controlled wear mechanisms, delaying the onset of micro-chipping and maintaining a more regular flank wear land.
Surface Quality: The brushed condition resulted in lower $R_a$ and $R_z$ values at both the beginning and end of the tool's life, attributed to the elimination of edge irregularities and a more stable cutting process. However, the untreated tool exhibited lower $R_{z1max}$ values, likely due to the larger edge radius of the brushed tool inducing a slight ploughing effect.

Significance
The paper concludes that abrasive brushing using SiC micro-abrasives is an efficient, cost-effective, and rapid method for engineering precise cutting edge microgeometries. By systematically optimizing parameters such as contact depth and brush angle, manufacturers can significantly enhance tool life and control surface quality during the milling of AISI P20 steel. The study highlights that while the brushing process introduces a specific edge radius that may slightly alter certain roughness metrics (like $R_{z1max}$ ), the overall benefits of defect removal and wear resistance make it a valuable industrial practice for improving machining reliability.

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