The Simpson CNW 5/8 in. to 1/2 in. Coupler Nut with Witness Hole is an engineered fastener from Simpson designed to connect threaded rods to one another and to anchor bolts in structural applications. Built to exceed the specified minimum tensile capacity of the corresponding bolts and threaded rod, this reducing coupler nut provides a dependable, verifiable connection when transitioning between a 5/8 in. diameter rod and a 1/2 in. diameter rod. A built-in positive stop promotes even thread engagement into each end of the nut, while the Witness hole gives installers a straightforward visual confirmation that both rods are properly seated before the connection is finalized.

Key Features

• Witness hole for visual installation verification - tighten the two rods until each all-thread rod is visible in the Witness hole, eliminating guesswork and reducing the risk of an under-threaded connection.
• Positive stop design - helps ensure even, consistent thread engagement into each end of the nut, promoting a balanced and reliable joint every time.
• Reducing diameter configuration (5/8 in. to 1/2 in.) - allows a direct, single-piece transition between two different rod sizes without additional adapters or hardware.
• Exceeds specified minimum tensile capacity - engineered to meet or surpass the tensile requirements of the corresponding bolts and threaded rod, supporting confidence in structural load-path connections.
• For non-hot-dip galvanized all-thread rod only - confirms correct material pairing upfront, helping buyers select the right coupler for their rod type and avoid compatibility issues on the job.
• Available in zinc plated or uncoated finish - provides finish flexibility to match project requirements or budget constraints.

Why This Product

• Built-in installation confidence - the Witness hole is a practical, field-ready feature that lets installers visually confirm proper rod seating without relying on feel or torque estimation alone, reducing costly rework or inspection failures.
• Engineered to exceed tensile capacity requirements - because the coupler nut is designed to surpass the minimum tensile capacity of the corresponding bolts and threaded rod, it supports the integrity of the full rod assembly rather than becoming the weak point in the connection.
• Single-piece solution for mixed-diameter rod runs - the 5/8 in. to 1/2 in. reducing configuration consolidates what might otherwise require multiple components into one compact coupler nut, simplifying installation in tight or congested framing conditions.
• Positive stop for consistent, repeatable results - whether connecting threaded rods to each other or to anchor bolts, the positive stop helps every installer achieve even thread engagement on both ends, supporting uniform performance across the connection.

Specifications

• Manufacturer Part Number (MPN): CNW5/8-1/2
• Brand: Simpson Strong-Tie
• Series: CNW
• Bolt/Rod Diameter: 5/8 in. to 1/2 in.
• Height (min.): 1-5/8 in.
• Finish: Zinc Plated or Uncoated
• Coating: 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 the CNW5/8-1/2 coupler nut?

The CNW coupler nut 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 have been threaded sufficiently into each end of the nut.

What rod sizes does the CNW5/8-1/2 accommodate?

This coupler nut is designed to connect a 5/8 in. diameter threaded rod on one end to a 1/2 in. diameter threaded rod on the other end, making it suitable for transitioning between two different rod sizes.

Can the CNW5/8-1/2 be used with hot-dip galvanized all-thread rod?

No. The CNW5/8-1/2 is intended for non-hot-dip galvanized all-thread rod only. For use with hot-dip galvanized bolts, Simpson Strong-Tie offers OST model couplers that feature oversized threads on one end to accommodate the thicker galvanized coating.

What is the purpose of the positive stop in the CNW coupler nut?

The positive stop is an internal feature of the CNW coupler nut designed to help ensure even threading into each end of the nut. It acts as a mid-point barrier so that both rods are threaded to a consistent and balanced depth, promoting proper thread engagement and structural integrity.

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