Polishing Textile Rollers from Ra 0.2 to Ra 0.13 with Diamond Abrasive Filament
Introduction
A textile machinery parts manufacturer in Shanxi Province came to us with a surface finish problem they had been fighting for months. Their textile rollers — the shaft-type components that guide and tension yarn in spinning and weaving equipment — needed a mirror-level finish. The starting point was Ra 0.2. The target was Ra 0.1 or better.
They had tried five different approaches. None of them reached the target.
This case study documents what we tested, what the data showed, and where the project stands today. It is based on an interview with Charlie Chen, our sales engineer who handled the project, recorded on September 18, 2026.
The Customer's Situation
Textile rollers are not a typical deburring application. These components run at high speed in continuous contact with yarn. Surface roughness directly affects yarn tension consistency, fiber damage, and the quality of the finished fabric. A roller that is too rough will abrade the yarn. A roller with inconsistent surface finish will produce uneven tension across the width of the machine.
The customer's rollers are made from hardened steel. The hardness is necessary for wear resistance, but it also makes polishing difficult. Hard materials resist abrasive cutting, and the harder the material, the faster the abrasive loses its edge.
The customer's target specification was Ra 0.1 or lower — a finish approaching mirror quality. Their starting point after conventional machining was Ra 0.2.
What the Customer Had Already Tried
Before contacting us, the customer had exhausted most of the standard options.
They started with ceramic abrasive brushes at various grits. The best result came from a 320 grit ceramic brush, which brought the surface from Ra 0.2 down to Ra 0.16. That was progress, but it was still 60% above the target.
They tried silicon carbide abrasive brushes. The results were similar to ceramic, with no clear improvement.
They tried aluminum oxide. Aluminum oxide is softer than silicon carbide and was not aggressive enough to cut the hardened steel surface effectively.
They tried polishing paste. Paste works well for final finishing but does not remove material efficiently at the Ra 0.2 to Ra 0.16 stage. The paste was polishing a surface that still needed to be cut.
They tried polishing fluid with the same result — good for lubrication and cooling, but not a cutting solution by itself.
The customer had never used diamond abrasive before. In their experience, diamond was for grinding wheels and cutting tools, not for brush polishing. It had not occurred to them that diamond filament brushes existed.
Why the Previous Approach Hit a Ceiling
The ceramic 320 grit result of Ra 0.16 was the best the customer had achieved. The question was why it stopped there.
Ceramic abrasive works by micro-fracture. The abrasive grains break down as they cut, exposing fresh cutting edges. This self-sharpening action is what makes ceramic effective. But on hardened steel, the fracture rate is too fast. The ceramic grains break down before they have time to cut effectively. The result is a surface that improves up to a point and then stops improving, no matter how many additional passes are run.
The customer had confirmed this empirically. Running the ceramic brush for four passes produced the same Ra 0.16 as a single pass. Additional passes were not removing more material — they were just wearing the brush.
This is a common limitation with conventional abrasives on hard materials. The abrasive is not hard enough to cut the workpiece efficiently, so the process stalls.
Our Solution: Diamond Abrasive Filament, 500 Grit
We recommended a diamond abrasive filament roller brush at 500 grit.
Diamond is the hardest abrasive available. It does not rely on micro-fracture to stay sharp — it maintains its cutting edge far longer than ceramic or silicon carbide. On hardened steel, diamond filament cuts where conventional abrasives stall.
The 500 grit specification was chosen based on the customer's target and starting point. Finer grits (800 and above) would produce a smoother surface in theory, but they remove material too slowly for the Ra 0.2 to Ra 0.13 range. The 500 grit provides enough cutting action to reduce the Ra while still producing a fine surface finish.
Key Data
The customer tested the 500 grit diamond filament brush on their existing equipment.
| Metric | Ceramic 320 Grit | Diamond 500 Grit |
|---|---|---|
| Achieved Ra | 0.16 | 0.13 |
| Passes required | 4 | 1 |
| Improvement per pass | Diminishing | Consistent |
Two results stand out.
First, the diamond brush reached Ra 0.13 — a 35% improvement over the ceramic result and much closer to the Ra 0.1 target.
Second, the diamond brush achieved this in one pass, compared to the four passes required by ceramic. In a production environment, this represents a 4x reduction in cycle time for the polishing operation.
The customer's equipment was limited to 1,500 RPM, with some machines capable of 2,000 RPM. Diamond filament performs well in this speed range. Higher speeds would improve the cutting rate further, but the existing equipment was adequate for the test.
Grit Is Not "Finer Is Better"
During the testing process, we also evaluated an 800 grit diamond filament brush.
The result was counterintuitive. The 800 grit brush produced a worse finish than the 500 grit — not better.
The reason is that 800 grit diamond filament is too fine to cut the hardened steel surface effectively. Instead of removing material, the filaments slid across the surface without engaging. The brush polished nothing because it was not cutting.
This is an important principle in abrasive brush selection. Finer grit does not automatically produce a finer finish. The abrasive must be coarse enough to cut the material it is working on. If the grit is too fine for the workpiece hardness, the brush will not remove material at all, and the surface finish will not improve.
For hardened steel, the practical grit range for diamond filament polishing is roughly 400 to 600. Below 400, the finish is too rough. Above 600, the cutting action becomes ineffective.
For softer materials — aluminum, brass, or mild steel — finer grits can be effective because the material is easier to cut. The correct grit depends on both the target finish and the workpiece hardness.
Next Step: Testing 600 Grit
The customer's target is Ra 0.1, and the 500 grit diamond brush reached Ra 0.13. There is still a gap.
The next step in this project is testing a 600 grit diamond filament brush. The 600 grit sits between the effective 500 grit and the ineffective 800 grit. It may provide enough cutting action to reduce the Ra from 0.13 to 0.10 while still producing a fine enough surface finish.
If the 600 grit does not reach the target, the next option would be a two-stage process: 500 grit diamond for the initial cut to Ra 0.13, followed by a finer diamond or ceramic brush as a final polishing pass.
This project is still in progress. We are following up with the customer on the 600 grit test results.
Frequently Asked Questions
Q: Can diamond filament brushes be used on a standard drill or polishing machine?
A: Yes. Diamond filament brushes mount in standard spindles, the same as any other abrasive brush. No special equipment is required. The customer in this case used their existing machines at 1,500 to 2,000 RPM.
Q: Is diamond filament more expensive than ceramic?
A: Yes, the initial cost is higher. However, diamond filament lasts significantly longer on hard materials and removes material more efficiently. In this case, one diamond pass replaced four ceramic passes. The cost per part is often lower with diamond, even though the brush itself costs more.
Q: What is the finest Ra achievable with diamond filament brushes?
A: It depends on the workpiece material and the starting surface. On hardened steel, Ra 0.1 is achievable with the correct grit and process. On softer materials, finer finishes are possible.
Q: Why did the 800 grit brush perform worse than 500 grit?
A: The 800 grit filaments were too fine to cut the hardened steel surface. They did not remove material — they just slid across the surface. The correct grit must be coarse enough to cut the workpiece material.
Q: Can I use diamond filament for aluminum or softer materials?
A: Yes, but diamond may be overkill for soft materials. Ceramic or aluminum oxide filament is usually sufficient for aluminum and brass. Diamond is most cost-effective on hard materials — hardened steel, carbide, and superalloys.
Q: Do you provide samples for testing?
A: Yes. We provide samples so you can evaluate the brush on your own equipment and parts. Contact us with your material, starting Ra, and target Ra, and we will recommend a specification.
Conclusion
This project is not finished. The 500 grit diamond filament brush reached Ra 0.13, which is progress but not the Ra 0.1 target. The 600 grit test is the next step, and we are following it through with the customer.
What the project has demonstrated so far is that conventional abrasives have a ceiling on hardened steel. Ceramic, silicon carbide, and aluminum oxide all stalled at Ra 0.16. Diamond filament broke through that ceiling because it stays sharp on hard materials.
For applications where conventional abrasives have stopped improving, diamond filament is worth testing. The initial cost is higher, but the cutting efficiency and tool life can justify the investment — particularly in production environments where cycle time matters.
Working on a polishing application where conventional abrasives have stalled?
Contact our team for a technical review. Send us your material, starting Ra, and target Ra, and we will recommend a diamond filament specification for testing.
Henry Zhu
International Sales Manager
Phone / WhatsApp / WeChat: +86 13818514531
Email: info@shlgbrush.com
Email: zhulei@shlgbrush.com
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