Myojin Cobalt Special COSP Petty 160mm Ebony Handle

A petty is a small utility knife, from the French petit. It is commonly shaped like a small gyuto and runs from 120 to 150 mm, up to 180 mm. Its clearest role is detailed work where a larger knife feels cumbersome: fruit peeling, garnish work, condiments, and small board work beside a gyuto or santoku.

A knife maker, Tojiro, frames the petty as a useful second knife, not an automatic necessity, and recommends santoku plus petty or gyuto plus petty combinations. It is not a replacement for a full size chef's knife; it lacks the blade length and belly for efficient chopping, rocking, or breaking down larger proteins. Treat it as a precision tool, not an all-rounder.

Petty knife lengths vary by maker: KAI's guide defines a petty (ペティナイフ) as a small knife with a narrow blade measuring 150 mm or under. Its table gives 90 to 150 mm, and it describes the shape as a smaller gyuto with a pointed tip.

We list petty knives from 70 mm to 165 mm, including lengths above the limit used in KAI's guide.

Cobalt Special (CoSP) is Takefu's stainless blade steel for cutlery: Takefu's page describes it as super high-grade and made by a special remelting process that gives a uniform composition and finely dispersed carbides.

Takefu's table gives 1.05% carbon, 16.00% chromium, 1.50% molybdenum, 0.25% vanadium, 0.25% tungsten and 2.50% cobalt, with a hardening hardness of HRC 60 or more. In Takefu's description, tungsten improves tempering resistance, molybdenum adds corrosion resistance, vanadium gives a finer microstructure, and cobalt strengthens the matrix and helps keep a long-lasting edge. Its 16.00% chromium is above the JSSA's 10.5% minimum for stainless, which the JSSA says strictly means rusts less; wash and dry the knife after use.

A hamaguri-ba edge, written 蛤刃, is a convex edge shape, and it is the shape the workshop 明神利器製作所 sharpens its knives to. Kochi City's craft page records that the workshop's second generation, whose name the page gives as 直人, learned it over several years of training in Fukui.

The same page says the workshop also takes sharpening-only orders from outside Kochi.

Yes. Kochi City's craft page for his workshop 明神利器製作所 says the work runs from forging through finishing in one continuous process, 鍛造から仕上げまで一貫して行う.

That page lists the workshop in Susaki, Kochi.