The Simpson CNW7/8-5/8 Coupler Nut with Witness Hole by Simpson is engineered to connect threaded rods to one another and to anchor bolts, making it a reliable choice for structural rod-to-rod transition connections. Designed to exceed the specified minimum tensile capacity of the corresponding bolts and threaded rod, this coupler nut bridges a 7/8 in. diameter rod on one end to a 5/8 in. diameter rod on the other, providing a secure mechanical link where two different rod sizes must meet. A built-in positive stop promotes even threading into each end of the nut, while the Witness hole gives installers a straightforward way to confirm that both rods are fully engaged before the connection is put into service.

Key Features

• Witness hole for visual installation verification - tighten the two rods until each all-thread rod is visible in the Witness hole, so you can confirm proper engagement without guesswork or disassembly.
• Positive stop feature - helps ensure even threading into each end of the nut, reducing the risk of uneven load distribution or under-threaded connections on the job site.
• Transition rod diameter: 7/8 in. to 5/8 in. - purpose-built to join two different rod sizes in a single coupler, eliminating the need for additional adapters in mixed-diameter rod assemblies.
• Minimum height of 2 in. - provides sufficient thread engagement depth on both ends to support the tensile demands of structural threaded rod and anchor bolt applications.
• Zinc plated or uncoated finish options - lets you match the coupler to the corrosion-protection requirements of your specific installation environment.
• For non-hot-dip galvanized all-thread rod only - clearly defined compatibility keeps the connection within its rated performance parameters and guides you toward the correct product for your rod type.

Why This Product

• Built-in installation confidence - the Witness hole is a practical, no-tools-required checkpoint that lets crews verify rod seating in real time, reducing costly rework caused by improperly threaded connections.
• Engineered for tensile performance - the coupler nut is designed to exceed the specified minimum tensile capacity of the corresponding bolts and threaded rod, so the connector is never the weak point in the assembly.
• Solves the mixed-diameter rod challenge - by accommodating a 7/8 in. rod on one end and a 5/8 in. rod on the other, this nut handles transition connections that a standard same-size coupler simply cannot, streamlining rod-system layouts that require size changes.
• Consistent threading depth every time - the positive stop takes the guesswork out of how far each rod should be driven in, promoting uniform engagement on both sides of the coupler for repeatable, code-compliant results.

Specifications

• MPN: CNW7/8-5/8
• Brand: Simpson Strong-Tie
• Series: CNW
• Bolt/Rod Diameter: 7/8 in. to 5/8 in.
• Height (min.): 2 in.
• Coating/Finish: Zinc Plated or Uncoated

Options

• Available in standard strength and high strength depending on corresponding rod in use
• Couplers available with oversized threads on one end for installation on hot-dip galvanized bolts (See OST models for ordering)
• OST couplers are typically oversized on one end of the coupler nut only and will be marked with an "O" on oversized side

Frequently Asked Questions

How do I know when the threaded rods are properly installed in this coupler nut?

The CNW7/8-5/8 features a Witness hole that allows you to visually verify proper installation. Tighten the two rods until each all-thread rod is visible through the Witness hole, confirming that both rods are fully and evenly engaged within the nut.

What rod sizes does the CNW7/8-5/8 coupler nut accommodate?

This coupler nut is designed to connect a 7/8 in. diameter threaded rod on one end to a 5/8 in. diameter threaded rod on the other end, making it ideal for transition connections between two different rod sizes.

Can this coupler nut be used with hot-dip galvanized all-thread rod?

No. The CNW7/8-5/8 is designed for non-hot-dip galvanized all-thread rod only. For use with hot-dip galvanized bolts, Simpson Strong-Tie offers OST models that feature oversized threads on one end to accommodate the thicker galvanized coating.

What is the purpose of the positive stop feature on the CNW coupler nut?

The positive stop is an internal feature built into the coupler nut that helps ensure even threading into each end of the nut. It acts as a centering mechanism so that both threaded rods engage with consistent and balanced thread depth, supporting the nut's ability to meet or exceed the specified minimum tensile capacity of the corresponding bolts and threaded rod.

Note: Product dimensions and/or screw or bolt holes may differ from picture. Please see item description for specifications.