Blade Curvature (反り)
Description
Blade curvature (sori) is the deliberate bow in scissor blades that controls contact pressure from pivot to tip. Essential for smooth closing action and clean cuts.
Blade Curvature (反り, そり / Sori — also おがみ / Ogami)
Quick look
- What it is: The critical lengthwise curvature along the inner face of each blade
- Measurement: Approximately 0.03mm, roughly one hair’s width
- Purpose: Forces blades to contact at a single moving point, creating true shearing action
- Creation: Achieved by hammer forging by hand, with no measuring instruments used
- Japanese terms: 反り (そり, sori) and おがみ (ogami)
Why it matters
Blade curvature is arguably the most critical and least understood element of scissor construction. This subtle lengthwise bow, measuring approximately 0.03mm (about the width of a single human hair), is what separates scissors that cut from scissors that merely close.
Without this curvature, both blades would contact each other along their entire length simultaneously. Hair would be trapped and folded between two flat surfaces rather than sheared. The curvature ensures that the blades meet at only one point at any given moment during closing, and that point travels progressively from the heel (near the pivot) to the tip. This moving contact point is what produces the clean shearing action that defines a quality cut.
Too much curvature and the blades press together too tightly. The scissors feel stiff, difficult to close, and fatigue the hand quickly. The excessive pressure also accelerates wear on the cutting edges.
Too little curvature and the blades fail to maintain contact. Hair folds between them instead of being cut cleanly. The stylist notices this as hair bending or pushing away rather than being severed.
What makes this dimension remarkable is how it is achieved. In traditional Japanese scissor making, blade curvature is created by hammer forging by hand. There are no measuring instruments involved. The craftsman judges the curvature entirely by eye and by the feel of the blade against a reference surface. This is a skill that takes years to develop and represents one of the clearest distinctions between handcrafted and mass-produced scissors.
| Related: Touch Point | Blade Spine | Hollow Grind |
Verified Sources
- Primary 🌐 HSC — Hairdressing Scissors Consortium (industry consortium)
Frequently Asked Questions
Because that tiny bow — roughly one human hair's width — is what turns a closing motion into a shearing action. Without curvature, both blades would meet along their entire length at the same moment, pinching hair between flat surfaces instead of cutting it. The curve forces the blades to contact at a single point, and that point travels progressively from heel to tip as the blades close. The moving contact is what produces the clean shear that defines a quality cut.
By hammer forging, entirely by hand, with no measuring instruments. The craftsman judges the curvature by eye and by the feel of the blade against a reference surface — a skill that takes years of apprenticeship to develop. This judgement-based process is one of the clearest distinctions between handcrafted and mass-produced scissors. Machine production can approximate the curve, but the human-forged version consistently reads correctly in the cut.
Too much curvature presses the blades together too tightly. The scissor feels stiff, difficult to close, and fatigues the hand quickly — and the excess pressure accelerates wear on both cutting edges. Too little curvature means the blades fail to maintain contact through the closure, and hair folds between them instead of being sheared. A stylist notices this as hair bending away or pushing rather than severing cleanly. The correct 0.03mm curve is the narrow range where both problems are avoided.