Sharpening does two things at once: it puts a fresh edge on the steel, and it decides how deep the groove between those edges is. The depth is what changes how the skate feels.
Technical derivationhighA sharpening wheel cuts a concave groove across the width of the blade. The radius of that groove is the hollow.
Two edges sit on either side of the groove. A smaller radius produces a deeper hollow and sharper edge angles, which bite harder into the ice. A larger radius leaves a shallower groove, so the blade releases more easily and glides further. Neither is better — they are two ends of one trade-off.
BOXPLAY treats the radius in millimetres as the primary unit, because that is how it is specified across most of Europe.
Radius of hollow in millimetres. A smaller radius cuts a deeper hollow: more edge bite, less glide. The position on this scale is BOXPLAY's ordinal placement, not a measured physical quantity.
The inch value in the table is a deterministic conversion of the millimetre radius to the nearest common ROH fraction — it is a derivation, not a second measurement, and it is rounded, so two different millimetre radii can share one inch label.
| Hollow (mm) | ≈ ROH (inch) | Bite | Glide |
|---|---|---|---|
| 10 mm | 3/8" | ||
| 12 mm | 1/2" | ||
| 13 mm | 1/2" | ||
| 14 mm | 9/16" | ||
| 15 mm | 9/16" | ||
| 16 mm | 5/8" | ||
| 18 mm | 11/16" | ||
| 20 mm | 3/4" | ||
| 22 mm | 7/8" | ||
| 25 mm | 1" | ||
| 28 mm | 1" | ||
| 30 mm | 1 1/4" | ||
| 32 mm | 1 1/4" | ||
| 35 mm | 1 1/2" | ||
| 38 mm | 1 1/2" | ||
| 40 mm | 1 1/2" |
What actually changes when you move along the spectrum.
Player weight and ice conditions both push you along this spectrum: heavier players and softer ice sink deeper into the surface, which already produces more bite. BOXPLAY does not publish a weight-to-hollow formula, because no manufacturer source validates one.
BOXPLAY assessmentmediumChange one variable at a time, or you will not know what caused the difference.
Next: blade profiling — the other half of how a skate blade meets the ice.