Turnbuckles are used in rigging to join wire-rope or cable to an anchor point or other length of wire. They have a screw thread for precise length and tension adjustment.
Most turnbuckles are forged or cast from stainless steel or low carbon steel. They are machined to product specifications and then quenched, tempered, plated with zinc, or hot-galvanized. Products with self-colored finishes and yellow chromate coatings are also available. Stainless steel turnbuckles are designed for applications that have high strength-to-weight ratios and minimum turnbuckle diameters. They combine very high tensile strengths with ductility and corrosion resistance. Some cable turnbuckles are made of 304 or 316 stainless steel. Others use 1030 carbon steel.
For all types of turnbuckles, there are several basic configurations:
- stub end
- eye and eye
- hook and hook
- jaw and jaw
- jaw and eye
Stub end turnbuckles feature a steel rod that protrudes at both ends. Eye and eye turnbuckles have two circular or oval-shaped eyes. Hook and hook turnbuckles and jaw and jaw turnbuckles have either two hooks or two jaws, respectively. Jaw and eye turnbuckles are designed for specialized applications.
Selecting turnbuckles requires an analysis of product and performance specifications. Basic measurements include diameter, take up, length, and estimated weight. To determine the extended length, turnbuckle suppliers usually add the amount of the take up to the length in the closed position. For turnbuckle eyes, specifications include: outer diameter (ID), inner diameter (ID), total diameter, eye thickness, and maximum load. Turnbuckle hooks carry specifications such as jaw type, throat opening, jaw thickness, maximum load, jaw ID, and total diameter. Measurements such as hole-center to jaw-end and hole-center to shank are also important considerations. Dimensions for turnbuckles are measured in English units such as inches and fractions of inches (in), or metric units such as millimeters (mm). Both types of turnbuckles can use either left-hand threads or right-hand threads. For inch-based turnbuckles, thread choices include: 10-32, 1/4-20, 1/4-28, 5/16-18, 5/16-24, 3/8-16, 3/8-24, 1/2 13, and 1/2-20. Metric turnbuckles carry thread designations such as M5 x 0.50, M6 x 1.00, M8 x 1.25, M10 x 1.50, and M12 x 1.75.
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