Brown Fused Alumina Grit Size Chart: F220 to F2000 Explained

Introduction

In the procurement and quality control of brown fused alumina micro powder, a grit designation such as “F360” alone rarely tells the full story. Products from different suppliers carrying the same F-number can vary noticeably in actual particle size distribution—and that variation is a common reason why quotes for nominally identical material diverge. This article sets out the complete FEPA 42-2 microgrit range from F230 to F2000, explains the three critical values behind every F-number (D3, D50, and D94), and offers practical guidance for using this data in specification and incoming inspection.

1. What the F-Number Actually Covers

FEPA (Federation of European Producers of Abrasives) defines abrasive grain sizes across two tiers. FEPA 42-1 covers macrogrits F4 through F220, intended mainly for bonded abrasives and general industrial grinding. FEPA 42-2 governs the microgrit series, spanning F230 to F2000. Brown fused alumina micro powder conventionally starts at F230. F220 sits at the boundary between macrogrits and microgrits; some suppliers offer it in microgrit-style grading, but strictly by FEPA classification the microgrit range begins at F230.

Crucially, an F-number does not correspond to a single particle size. It defines a distribution band. Three values anchor that band: D3 (coarse-end limit), D50 (median diameter), and D94 (fine-end limit). Whether two suppliers’ F360 materials are genuinely equivalent depends on where their measured distributions fall within those limits.

2. Complete Grit Size Data: F230 to F2000

The following values are drawn from FEPA 42-2. D3 indicates that no more than 3% of particles may exceed the stated size. D50 is the median diameter, with 50% of particles below and 50% above. D94 indicates that at least 94% of particles must be larger than the stated value.

Note: For F1200, F1500, and F2000, the fine-end criterion is assessed at D80 rather than D94. Some sources list F2000 median diameter as 1.2 ± 0.3 μm.

3. F360 as a Case Study: Why Distribution Drives Price

F360 is one of the more widely used mid-to-fine microgrits. Under the standard, its D50 must fall within 22.8 ± 1.5 μm, with D3 no coarser than 40 μm and D94 no finer than 12 μm. That range may look narrow, but it leaves meaningful room for variation in production.

A supplier who holds D50 close to the midpoint and keeps both D3 and D94 on the tight side of the tolerance band needs finer classification equipment and longer processing time—costs that show up in the price. Another supplier who merely “meets spec”—D50 near the boundary, coarse end approaching 40 μm, fine end barely at 12 μm—will deliver material that behaves differently in grinding efficiency, surface finish consistency, and batch-to-batch reliability. The price gap between two F360 quotes is, in most cases, a reflection of how tightly the particle size distribution is controlled, not a difference in the standard itself.

4. Practical Recommendations

When requesting quotes or conducting incoming inspection, combine the grit designation with measured distribution data:

1. Ask for batch-specific D3/D50/D94 values, not simply an “F360” label;

2. For precision polishing or applications with strict surface quality requirements, agree on a tightened internal specification within the standard range (for example, D50 22.0–23.5 μm, D3 ≤ 36 μm);

3. Include particle size distribution alongside chemical composition (Al₂O₃ content, magnetic material) in acceptance criteria, rather than relying on the F-number alone.

Conclusion

The F-number is a starting point for communication about brown fused alumina micro powder, not an endpoint. Across the F230–F2000 range, each designation represents a distribution band measured in microns. Understanding D3, D50, and D94—and insisting on measured data in both procurement and quality control—is the most direct way to avoid “same number, different material.”