Loctite 640 is a high-strength adhesive for wide diameter cylindrical parts.

A 1-part, low-viscosity, high-strength retaining compound with optimal temperature resistance. Extended cure time is ideal for parts requiring longer positioning time, like large diameter or active metal parts like brass.

LOCTITE® 640™ is intended for bonding cylindrical fitting parts. The product cures in the absence of air between close metal surfaces and prevents loosening and leakage from shock and vibration. Typical applications include retaining keys and splines, eliminating backlash in worn assemblies, and augmenting press fits.

Technical Data:

This high-strength adhesive typically achieves a fixture time of 2 hours on steel and withstands service temperatures ranging from -55°C to 175°C (-67°F to 347°F) when fully cured. It offers a maximum diametrical clearance of 0.1 mm (0.0004") and fluoresces under UV light, making it ideal for quality control. It is well-suited for applications such as retaining keys and splines, eliminating backlash in worn assemblies, securing bearings to prevent spin-out, fixing rotors to shafts in fractional and sub-fractional horsepower motors, holding bushings and sleeves in housings and on shafts, enhancing press fits, and restoring the fit of worn or out-of-tolerance parts. Additionally, it is used in applications that adhere to the Mil-R-46082 military specification.