Silicon Carbide vs Aluminium Oxide Abrasive Filament Brushes
Comparison · 6 min read · updated 2026-10-24
Abrasive nylon brushes are made from nylon monofilament with abrasive grit mixed through it, so every filament cuts along its sides as well as its tip. Two grains dominate: silicon carbide (SiC) and aluminium oxide (Al2O3). Ceramic grain is a third, more aggressive option.
The choice of grain matters less than many catalogs suggest — diameter, grit size and loading usually matter more — but there are real differences in hardness, toughness and suitability for particular metals.
The grains compared
Hardness figures are from the nylon filament maker's technical bulletin, which also gives ceramic aluminium oxide as the most aggressive of the three grains because it fractures to form fresh sharp edges.
| Property | Silicon carbide | Aluminium oxide |
|---|---|---|
| Knoop hardness | 2480 | 2100 (fused alumina) |
| Grain character | Harder, sharper, more brittle | Tougher, less likely to fracture |
| Market share in abrasive filament | Most common | Widely available |
| Typical strengths | Non-ferrous metals, cast iron, wood, plastics, stone | High-tensile metals such as steel and stainless; finishing softer metals |
| Iron in grit | <0.1% iron oxide, no free iron (supplier data) | Not specified in the same data |
How much difference does the grain make?
Less than you might expect. The filament maker states that with diameter and grit equal, the difference in metal removal between SiC and aluminium oxide filaments is not clear-cut, and short tests have shown aluminium oxide working well even on steel parts. SiC is used most because it is harder and thought to be more durable.
Our view for buyers: pick the grain by workpiece and finish target, then spend most of your attention on filament diameter, grit and trim length, which change brush behavior far more.
When to choose silicon carbide
Examples: our 150 mm SiC 80 grit disc brush for CNC face deburring and a SiC 180 grit wound roller for sanding and rust-removal lines.
- Aluminium parts: SiC grit carries negligible iron, so it will not seed corrosion on aluminium.
- Cast iron, non-ferrous metals, wood structuring and denibbing, plastics and stone.
- Fast general deburring where a sharp, hard grain helps.
When to choose aluminium oxide
Example: our 350 mm aluminium oxide 120 grit CNC disc brush, offered in grits from 46 to 1000.
- Steel and stainless parts, where a tougher grain resists fracturing.
- Applications where a slightly milder, more even action is wanted.
- Edge radiusing and finishing of aluminium castings where a consistent finish matters more than raw cut.
Ceramic grain, heat and break-in
Ceramic aluminium oxide is the third grain. It fractures easily to expose new sharp edges, which the filament maker rates as the most aggressive of the three, at a higher price. It suits fast stock removal and hard alloys; see our 2 in ceramic grain disc brush.
Whatever the grain, the nylon carrier controls stiffness. Nylon filament is about twice as stiff at 0 °C as at room temperature and loses roughly another half of its stiffness by 60 °C, so dry high-speed brushing can soften the tips; coolant or lower speed helps. New brushes also cut harder for a while until fresh grit and filament moisture reach equilibrium, which can take minutes to hours, so judge performance after break-in.
Grit, diameter and loading: the bigger levers
- In a tufted brush, stiffness rises with the square of filament diameter — small diameter changes make a big difference.
- Moving from 80 to 120 grit in the same filament gives about 50% more grit particles at the surface.
- Grit loading is normally 20–40% by weight; going from 30% to 40% adds about a third more grit, but above 40% filament durability drops noticeably.
| Filament diameter | Typical grit | Typical use |
|---|---|---|
| 1.5–1.8 mm (0.060–0.070 in) | 46, 36 | Floor stripping, heavy scale, wood structuring |
| 1.0–1.3 mm (0.040–0.050 in) | 80, 120 | Aggressive scrubbing, deburring |
| 0.76–0.89 mm (0.030–0.035 in) | 180, 240 | Deburring, finishing |
| 0.30–0.56 mm (0.012–0.022 in) | 120–600 | Fine finishing, buffing |
Selection checklist
- Workpiece: aluminium or non-ferrous → SiC first; steel or stainless → either, aluminium oxide is a good default.
- Goal: burr removal → coarser grit and larger filament; cosmetic finish → finer grit, smaller filament.
- Wet or dry: nylon softens with heat and moisture; coolant helps in high-speed dry work.
- Brush format: disc, wheel, end, cup or roller — browse abrasive nylon brushes.
- Brush makers can buy our SiC / Al2O3 bulk filament at 20–40% abrasive load. See also abrasive nylon vs wire wheels. Send your part material and grit to Request a Quote.
Frequently asked questions
- Is silicon carbide harder than aluminium oxide?
- Yes. Published Knoop values are about 2480 for silicon carbide and 2100 for fused alumina. Silicon carbide is harder and sharper; aluminium oxide is tougher and fractures less.
- Which abrasive nylon is best for aluminium?
- Silicon carbide is the common choice because its grit contains almost no iron, so it will not cause iron-contamination corrosion. Aluminium oxide is also used for finishing aluminium castings.
- Which abrasive filament is best for steel?
- Aluminium oxide is a common default on steel and stainless because the grain is tough. Silicon carbide also works; in practice grit size and filament diameter affect results more than the grain.
- What grit should I use for deburring?
- Parts-finishing brushes commonly use 120–240 grit on 0.56–1.0 mm filament; heavy burrs call for 80 grit on larger filament, and fine finishing for finer grit. Test on a real part.
Related products
Need help choosing or a custom spec?
Send us your machine, drawing or requirement — we'll match the right brush and quote, usually within one business day.