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SPS Technologies’ Preload Indicating Washers Help Maximize Joint Strength

July 29, 2005

JENKINTOWN,Pa. –SPS Technologies Aerospace Fasteners offers Preload Indicating Washers (PLI) which provide an accurate method of measuring the preload (clamp force) in a bolted joint. Using Preload Indicating Washers to achieve maximum preload allows designers to maximize joint strength. Frequently smaller diameter fasteners or fewer fasteners can be used, reducing weight without reducing joint reliability. SPS PLI washers are also useful with joints that are inaccessible to torque wrenches. No special tooling is required in the application of these washers.

Three types of PLI washers are available; the standard washer is designed for use under locknuts to induce an average preload of 80% of the yield strength in bolts ranging from 80 ksi to 260 ksi minimum ultimate tensile strength.

An under-the-head version is used in applications where space limitations make it impossible to install an under-the-nut washer, and oversize PLI washers are for use with re-worked joints.

Sizes range from #10 to 1-1/2” diameters in alloy steel, cadmium-plated to QQ-P-416 and corrosion resistant A286 material, passivated to ASTM A967 specifications.

SPS product engineers, supported by an experienced technical staff, are available to help in product design and material selection.

SPS Technologies is a leading developer, manufacturer and global supplier of a comprehensive line of aerospace fasteners and precision components. SPS products are used in commercial and military aircraft, jet engines and other critical applications.

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