Blade geometry is the specification that changes what techniques a shear can perform, and it is almost never explained on a product page. Two shears in the same steel at the same length can be completely different tools depending on how the edge is ground. If you have ever tried to slice cut with a shear that snagged and pushed the hair instead of gliding through it, you have met the wrong geometry.
The two edge families
Bevelled (German-style) edges
A bevelled edge is ground flat at an angle, usually 40–50 degrees, often with a micro-serration on one blade to grip the hair and stop it sliding forward. Bevelled shears are robust, cheap to produce, easy to sharpen and very forgiving of poor technique. They are excellent for blunt cutting on wet hair.
The serration is the limitation. It grips the hair deliberately — which is exactly what you do not want when you are trying to let the hair travel along the blade.
Convex (Japanese-style) edges
A convex edge is ground on a curve, both faces sweeping smoothly to a very acute apex — typically in the region of 35–45 degrees, with no serration at all. The result is a razor-type edge that parts hair rather than pinching it. Convex blades are what make silent, glass-smooth cutting possible, and they are the only geometry that slice cutting genuinely works on.
They are also less forgiving: an acute convex edge chips if abused and needs a specialist to sharpen properly. That is the trade you accept for the technique range.
Where "hollow ground" fits
Hollow grinding is a separate operation from the edge grind, and confusing the two is common. Hollow ground refers to the concave scoop machined into the inside face of the blade, behind the cutting edge.
Its purpose is contact reduction. Without it, the two blade faces would ride against each other along their whole length, creating friction, heat and drag. The hollow means the blades touch essentially only at the point where they cross. An extreme hollow ground blade takes that further, reducing contact to a minimum.
Practical consequences:
- Far less friction, so the shear runs cooler and quieter.
- Lighter tension can be used, which reduces hand fatigue over a full day.
- The cut is smoother and the blades stay sharp longer, because they are wearing against each other less.
Hollow grinding and convex edges are frequently combined — an extreme hollow ground convex blade is the standard construction for a serious Japanese-style cutting shear. That is the geometry on the OTTO 6" Professional Shear, whose product page specifies extreme hollow ground convex blades.
Slice cutting: what it needs and why
Slice cutting (also called slide cutting or slithering) means opening the blades slightly and drawing them down the hair shaft while gradually closing them, removing length and weight progressively and leaving a soft, tapered end.
The technique depends on the hair being able to travel along the blade while it is being cut. A convex edge allows that. A serrated bevelled edge stops it dead — the serration grips, the hair bunches, and you get a chewed, pushed result instead of a clean taper. Attempting slice cutting on a serrated shear is not a technique problem; the tool physically cannot do it.
Doing it well
- Dry hair only. Wet hair stretches and drags, and you cannot see the result until it dries — by which point you have taken too much.
- Keep the blades barely open. A wide angle removes far more than you intend.
- Move continuously. Stopping mid-stroke leaves a visible step.
- Work the mid-lengths and ends. Slicing into the root area creates short pieces that stand up.
- Less than you think. Slice cutting is cumulative; the result appears over several passes.
Which geometry should you buy?
- Blunt cutting on wet hair, structured graduation, learning → a bevelled shear is competent and forgiving.
- Slice cutting, point cutting, dry detailing, soft texture, any modern layering → you need convex. There is no substitute.
- A single shear that does both → convex. It will do blunt work perfectly well; the reverse is not true.
Caring for a convex edge
Acute convex edges are the most vulnerable to damage. Never let the blades touch metal — no clips, no pins, no dropping into a drawer with clippers. Never use a cutting shear on foil, paper, elastics or extension tape. And never let a general sharpener near it: a convex edge must be sharpened on a flat rotary hone by someone who works on Japanese-style shears, and a bevelled-style sharpening will destroy the geometry permanently. Full routine in our care, oiling and sharpening guide.
Bottom line
Steel grade decides how long an edge lasts. Geometry decides what the edge can do. If slice cutting, point cutting and soft dry texture are part of your work, convex is not an upgrade — it is a requirement, and an extreme hollow ground convex blade is the construction to look for.
Shop the Otto range
Every Otto tool is listed in Canadian dollars with current stock on the Otto collection. Prices quoted in this guide were correct at the time of writing — the product page is always the authority.