Machine Sharpening (機械研ぎ)
SharpeningChoose a service route from the exact tool and proposed work
Provider labels matter less than demonstrated capability, custody, process, and the evidence returned with the tool. Apply to Machine Sharpening (機械研ぎ)
- 01 Identify the tool Record model, handedness, edge, blade pair, teeth, pivot, history, and symptoms.
- 02 Vet capability Ask about exact geometry, equipment, cooling, parts, warranty, and examples.
- 03 Scope the work Require intake findings, proposed material removal, adjustment, parts, and exclusions.
- 04 Verify return Record work performed, inspection, baseline action, aftercare, and next escalation route.
Do not inferA machine name, mirror finish, paper cut, mail-in badge, price, or claimed certification cannot by itself prove original-geometry restoration.
Description
Machine sharpening runs an edge on a powered grinding system. Where the method fits, where a convex blade needs a different approach, and what to ask.
Machine Sharpening (機械研ぎ - Kikai-togi)
Machine sharpening (kikai-togi) is edge work on a powered grinding system, usually a fixed-speed wheel or disc, and in the inherited sharpening sources it is associated with beveled (dan-ba) edges rather than with the curved face of a convex (hamaguri-ba) blade. Its appeal is speed and repeatability; its limit is the geometry it can follow.
Quick look
- What it is: Sharpening on a powered grinding system, typically at fixed speed
- Cited system: Wolff Twice as Sharp, which the inherited account gives at 3,450 RPM
- Documented match: German-style beveled (段刃 / dan-ba) edges
- Known limit: A flat grinding surface does not follow a convex (hamaguri-ba) curve unless the operator deliberately does so
Why it exists
Machine sharpening delivers speed and consistency for beveled-edge scissors. The Wolff Twice as Sharp system, which the inherited sources describe at a fixed 3,450 RPM, is widely cited for bevel work in the United States and internationally. It produces a repeatable bevel angle with little operator variation.
For salons running large inventories of beveled scissors, that repeatability is the point. The inherited source figures put a beveled pair at 5 to 10 minutes with a skilled operator; ask for a current quote instead of relying on that number.
The convex problem
A fixed speed and a flat grinding surface cannot follow the continuous curve of a convex edge, so the operator has to compensate deliberately or the curve flattens into a bevel. That removes material the maker’s geometry depended on, and once the hamaguri-ba radius is ground away it cannot be restored without further metal loss and professional re-grinding.
Hikari’s published position is that unsuitable machine or self-taught grinding can damage its convex edges permanently. That is a maker warning about specific work, not proof that every machine process ruins every convex scissor: repairability and method belong to the particular tool, which is why the question to ask is how the service preserves this model’s geometry.
If your scissors have a convex edge, use a method that keeps the convex profile. Compare hand sharpening and a togishi service, or the maker’s own service route.
When machine sharpening is the documented match
| Scenario | Assessment |
|---|---|
| German-style beveled scissors | The documented match for a flat grinding surface |
| High-volume beveled inventory | Fast and repeatable, which is the method’s advantage |
| Training scissors with micro-serration | Ask the sharpener; the source material does not establish a general rule |
| Japanese convex scissors | Only with a method that keeps the convex profile; ask the sharpener or use the maker’s service |
| Semi-convex edges | Ask the sharpener before handing them over |
What to expect
- Turnaround: the inherited source figures put beveled work at 5 to 10 minutes per scissor
- Price: usually below hand work in the same account; ask for a current written quote
- Consistency across multiple scissors is the method’s strength
- The sharpener should still check tension, alignment and pivot condition
Related links
Sources and limits
A machine name, a speed in RPM or a national edge stereotype does not establish suitability for a particular scissor. The RPM and time figures here are inherited source examples, and the convex warning is Hikari’s maker statement about its own edges. Deciding a service means asking how it preserves the exact model’s edge, ride, hollow and blade set, whether it handles the handedness and tooth system, and what the maker’s service terms say about third-party work.
- Wolff Industries–Twice as Sharp System
- Dark Stag–Convex vs. Bevelled vs. Serrated
- Hairfinder–Difference Between Convex and Beveled Shears
See Also
Sources
1 source- Hairfinder — Slide Cutting (reference)
Frequently Asked Questions
3 answers you can open one at a timeWhy is machine sharpening a poor match for convex (hamaguri-ba) edges?
A machine set up for flat bevels can flatten a convex curve if the operator does not follow it, and the original curve is then hard to restore. Hikari warns that unsuitable machine or self-taught grinding can damage its convex edges. That is not a universal consequence of one equipment category, so ask any sharpener, machine or hand, how they will keep this model’s curve.
Which scissors are the natural match for machine sharpening?
German-style beveled (dan-ba) edges are the documented match, because a flat grinding surface follows a straight bevel angle and fixed-speed repeatability suits large beveled inventories. Semi-convex edges need the sharpener’s judgement before you hand them over, and convex scissors need a method that keeps the convex profile. A machine name or speed does not establish suitability for a particular scissor.
How much does machine sharpening cost and how long does it take?
The inherited source figures put a beveled scissor at 5 to 10 minutes on a machine, usually below the price of hand work; ask for a current written quote rather than relying on those numbers. That turnaround is why machine sharpening suits high-volume beveled inventory. A competent sharpener should still check tension, alignment and pivot condition rather than only running the edge through the wheel.
Comments & questions
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