White Fused Alumina Grit for Grinding: How to Select a Grade
白色電融アルミナ (WFA) is used in bonded abrasives, coated abrasives and selected loose-abrasive grinding processes. その高い硬度, relatively friable grain and low iron profile support clean cutting and controlled finishing. しかし, choosing a grade by grit number alone can lead to slow removal, short tool life or an inconsistent surface.
The correct choice depends on the workpiece, abrasive product, bond, machine, pressure, coolant and target finish.
Where WFA Is Used in Grinding
- Bonded abrasives: vitrified and resin grinding wheels, mounted points and stones.
- Coated abrasives: paper, cloth, film, belts and discs using the required P-grade distribution.
- Loose abrasive processes: selected lapping, fine grinding and polishing systems.
- Surface preparation: clean abrasive blasting and controlled finishing.
Start With the Workpiece
WFA is commonly evaluated for hardened steel, tool steel, stainless components, セラミックス, glass and other materials where sharp cutting or low contamination is important. It is not always the most economical choice for heavy grinding of general steel, where tougher brown fused alumina, zirconia alumina or ceramic grain may provide longer life.
| Process goal | Selection priority |
|---|---|
| Fast stock removal | Coarser grade, suitable toughness, open tool structure and adequate power |
| Cool precision grinding | Sharp/friable grain, correct bond and controlled infeed |
| Fine surface finish | Finer distribution, oversize control and clean process |
| Low iron contamination | Agreed chemistry and magnetic-material limit |
| Long tool life | Balance grain friability with bond strength and operating pressure |
FEPA F vs FEPA P
FEPA F grades are associated with bonded abrasives and general applications. FEPA P grades are intended for coated abrasives. Similar-looking F and P numbers are not direct equivalents because their distribution limits and test methods differ.
For microgrits or loose abrasive use, JIS or customer-defined micron distributions may apply. A conversion chart is only a starting point; approve the actual distribution and process result.
Grain Shape and Bulk Density
Particle shape influences cutting action, packing and abrasive-tool structure. Sharp angular grains may cut aggressively, while more blocky shapes may behave differently under load. Bulk density reflects how a mass of grain packs under a defined test method and is affected by shape and size distribution.
Do not specify high density without naming the method and acceptable range. A value from another procedure may not be comparable.
Bond and Process Conditions Matter
In a grinding wheel, grain performance cannot be separated from the vitrified or resin bond, porosity, grade and structure. In a coated abrasive, backing, resin, electrostatic orientation and coating weight affect life and finish. In loose grinding, slurry concentration, plate, pressure and dispersion may dominate results.
Abrasive raw material should therefore be tested in the finished tool or actual process, not judged only by a laboratory hardness number.
Common Problems and Checks
| Problem | What to investigate |
|---|---|
| Burning or discoloration | Grit, wheel grade, dressing, coolant, speed and infeed |
| Low removal rate | Grade too fine, dull grain, glazing, weak pressure or unsuitable abrasive |
| Short wheel/belt life | Grain too friable, bond too soft, excessive pressure or poor coating |
| Random scratches | Oversize particles, contamination, dirty coolant or previous process grit |
| Batch-to-batch variation | Distribution, shape, bulk density, chemistry and tool-production conditions |
Information for a Supplier
- bonded, coated or loose-abrasive process;
- workpiece material and hardness;
- current FEPA/JIS/micron grade;
- tool type, machine speed and wet/dry conditions;
- target removal rate and surface finish;
- critical chemistry, bulk density or oversize limit;
- monthly quantity, packaging and destination.
See the WFA grit standards guide and our white fused alumina micro powder. Request a representative sample and specification review.
