Concave Blade and Inner Hollow
Edge typesKeep the edge term attached to geometry and service
An edge label becomes useful only when its maker wording, host blade, finish, and service route are known. Apply to Concave Blade and Inner Hollow
- 01 Record the term Preserve the exact maker and model wording.
- 02 Locate the edge Identify the blade half, section, line, and any serration.
- 03 Trace its condition Keep sharpening, damage, coating, and inspection history.
- 04 Choose service Ask how the provider will preserve the original geometry.
Do not inferPolish, shine, feel, or a marketing label cannot diagnose an edge geometry or authorise a sharpening method.
Concave must name the face and view
The word can refer to an outer form, an inner-face hollow, or a maker-local category. Those are not interchangeable.
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01 Side / plan view Unresolved
Blade line
Concave does not reveal whether the word refers to a plan-view line.
Leave openHeel-to-tip path and the axis being described remain unknown.
The available label does not reveal the geometry or measurement axis.
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02 End-on slice Maker-local
Cross-section
An inward-curving inner face is one possible, source-dependent reading.
Leave openDepth, extent, contact surfaces, symmetry, and partner blade remain open.
Keep the term attached to the maker, model, language, and dated source.
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03 Magnified working edge Open field
Edge / grind
Inner hollowing does not identify the final outer cutting edge.
Leave openEdge grind, finish, serration, condition, and service method remain open.
This route does not settle the field; record it separately.
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04 Declared axis + view Unresolved
Spatial curve
Face and measurement axis must be declared before comparison.
Leave openInner versus outer face, end-on location, lighting, scale, and datum remain unknown.
The available label does not reveal the geometry or measurement axis.
Description
Concave can describe an outer blade form, a hollow-ground inner face, or an imprecise translated listing. These are separate from the final edge grind and must be verified from the exact maker diagram.
“Concave” is ambiguous in shear listings. It may name a maker’s outer blade form, the hollow-ground relief on an inner face, or a loose translation of another construction. None of those automatically defines the final edge grind, and a photograph rarely resolves the difference.
Three Different Fields
| Field | What to record | What not to infer |
|---|---|---|
| Outer concave blade form | Maker term and section drawing for each blade half | Inner hollow, convex edge, technique, or cutting load |
| Inner hollow or relief | Location, depth, contact or ride surfaces, and maker wording | Outer grind, final edge, or universal friction reduction |
| Final edge grind | Convex, beveled, serrated, or other maker-specified finish | Whole-blade section or inner-face construction |
Joewell’s blade guide includes a maker category called Concave Blade and attaches a lower-cutting-load claim to that Joewell category. That is not proof that every listing containing “concave” describes the same cross-section or produces the same result.
Inner Relief Is Not the Outer Grind
KASHO describes named models as convex on the outside and hollow-ground on the inside. OKAWA describes the SG-X with hand-ground hollow blades. These model-level statements show why both faces must be recorded separately; neither construction should be exported to an unrelated model from the word concave alone.
A ride line or contact surface is also not a synonym for the entire hollow. Record the surfaces a maker identifies, but do not assume their width, depth, wear pattern, or function is standardized across brands.
Inspection Checklist
When a catalogue says concave or hollow-ground, ask:
- Which face and which blade half does the term describe?
- Is there a maker cross-section drawing rather than only a product photograph?
- What outer grind and final edge treatment are specified separately?
- Are contact or ride surfaces identified and dimensioned?
- Is the claimed outcome a measured specification or maker performance wording?
- What service route preserves the exact construction?
Service Boundary
Inner relief, outer form, edge, blade set, and alignment are serviced as one blade pair. The label does not determine a stone, wheel, pressure, oiling routine, service interval, or economic replacement threshold. Follow the maker’s repair specification or use a technician who can identify the geometry before removing material.
See Also
Convex Edge → · Blade Cross-Sections → · Scissor Anatomy → · Sharpening →
Sources
3 sources- Joewell Scissors — Official Japan (manufacturer official)
- Kasho / KAI Corporation (manufacturer official)
- 🇯🇵 OKAWA pro-scissors (オオカワプロシザーズ) (manufacturer official)
Frequently Asked Questions
4 answers you can open one at a timeDoes "concave blade" always mean an inner hollow?
No. Joewell uses Concave Blade as one category in its blade-shape guide, while other listings use concave or hollow-ground for relief on the inner face. A maker’s section drawing is needed to distinguish an outer blade form from inner relief.
Is an inner hollow the same as a convex edge?
No. Inner hollowing describes relief on the inside face; convex describes an outwardly rounded outer grind or blade surface. KASHO publishes named models with both features, demonstrating that they are compatible but separate specifications.
Does hollow grinding guarantee lower friction or longer edge life?
A maker may state a purpose for its own construction, but the label alone does not quantify contact area, closing force, wear, or service life. Depth, ride surfaces, blade set, finish, alignment, and the partner blade all matter.
Can every damaged inner hollow or ride surface be restored?
Repairability depends on the exact construction, remaining material, damage, and maker tolerances. Do not infer a repair method or replacement threshold from the word concave. Ask the maker or a technician qualified for that model.
Comments & questions
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