How to Choose the Ideal Coupling Nut

Coupling nuts are required when connecting two threaded rods together. Slightly different than a sleeve nut, a hex coupling nut offers right hand threads and can be tightened or loosened using standard socket sets and wrenches. These specialty fasteners are useful in many applications, provided the right grade and length is chosen.
Different Grades of Coupling Nut
When ordering coupling nuts for your project consider the compatibility of nut to bolt, keeping in mind any applicable specifications. If the ASTM nut grade is compatible to the grade of your nut, the same coupling nut grade should be chosen. These fasteners do not take the place of a rod, but instead act as a bridge for the bolts or rods involved.
Sometimes termed as hex couplers, these fasteners come in both plain and galvanized, as well as in a range of other metals for superior performance in any environment. When hot dip galvanized processes are used coupling nuts must be tapped oversize to accommodate the coating found on both the nut and the corresponding bolts.

Choosing the Best Length
Most coupling nuts should be about three times the diameter of the bolt or rod involved. You can opt for something shorter, but understand that your joint will be weaker and more prone to failure under heavier pressures. This kind of shorter length is found mainly in mass-produced lines.
Engineers and fastener distributors will agree that a coupling nut is not a substitute for a rod. Although this type of fastener connects two rods for a solid line, it cannot offer the same stability as a solid rod. You may be able to opt for longer coupling nuts, but the joint remains vulnerable. Many applications require testing and an engineer’s stamp to ensure the safety of this unit.
Commonly available in 1/2-inch to 1-inch diameters and made both onshore and offshore, coupling nuts provide a simple, effective solution when combining two bolts or rods together. With the proper expectations and an understanding of nut compatibility, you can choose the ideal coupling nut for your project. Contact your fastener distributor for a competitive price quote today.