jakoavaimen

Jakoavain, also known as a adjustable wrench or crescent wrench in English, is a hand tool used to tighten or loosen nuts and bolts of various sizes. It consists of a fixed jaw and a movable jaw connected by a handle; the gap between the jaws is adjusted by a screw mechanism, typically a knurled worm gear, allowing it to fit different fastener sizes.

Design and materials commonly include a steel body, often chrome-vanadium steel, with a rust-resistant finish. Many models feature a scale on the jaw or body in metric and sometimes imperial units to aid sizing, although precise measurement is not essential for most tasks. The movable jaw is guided by the adjustment screw to ensure parallel jaws and stable grip.

Operation typically involves placing the fixed jaw against the nut or bolt head, then turning the adjustment screw until the movable jaw grips securely. The tool should be kept level on the fastener to avoid rounding corners, and force should be applied to the handle rather than the jaw. Some models have a longer handle for increased leverage, while compact versions are designed for confined spaces.

Sizes and variants range from small models with a jaw capacity around a few millimeters to larger ones that open up to 24 millimeters or more. Common forms include standard adjustable wrenches with a flat, smooth jaw and, in some cases, features such as a built-in ruler, reversible jaws, or coatings for enhanced durability.

History and adoption: the modern adjustable wrench was developed in the late 19th century, with early patents attributed to Johan Petter Johansson of Sweden in 1891. Since then, the tool has become widespread in professional and domestic repair work, with numerous brands and regional standards.