The Simpson CNW3/4-3/4-OST Oversized Thread Coupler Nut with Witness Hole from Simpson is engineered to connect 3/4 in. threaded rods to one another and to anchor bolts in demanding structural applications. Built to exceed the specified minimum tensile capacity of the corresponding bolts and threaded rod, this coupler nut features oversized threads on one end for reliable installation onto hot-dip galvanized bolts, a built-in positive stop for consistent, even threading into each end, and a Witness hole that gives installers a clear visual confirmation of proper rod engagement before any load is applied.

Key Features

• Witness hole for visual rod verification - tighten the two rods until each all-thread rod is visible in the Witness hole, giving installers immediate, on-the-spot confirmation that thread engagement is correct before load is applied.
• Oversized threads on one end - designed specifically for installation on hot-dip galvanized bolts, allowing proper fit where standard thread clearance is insufficient.
• Single-end OST design marked with an "O" - the oversized side of the coupler nut is clearly identified, eliminating guesswork during installation and reducing the risk of misalignment.
• Built-in positive stop - helps ensure even threading into each end of the nut so load is distributed consistently across the connection.
• Exceeds specified minimum tensile capacity - engineered to meet the strength demands of the corresponding bolts and threaded rod, supporting confidence in structural rod-to-rod and rod-to-anchor-bolt connections.
• Zinc plated finish available - provides a corrosion-resistant coating suited to a range of interior and protected structural environments.

Why This Product

• Built-in installation verification - the Witness hole removes uncertainty from the installation process. Rather than relying on feel or thread count alone, installers can visually confirm that both rods are fully engaged, reducing the chance of under-threaded connections in critical structural assemblies.
• Purpose-built for hot-dip galvanized hardware - the oversized thread on one end of this coupler nut is designed to accommodate the added coating thickness of hot-dip galvanized bolts, making it the right choice for connections where standard-thread couplers will not fit correctly.
• Strength engineered to match the rod and bolt - because this coupler nut is designed to exceed the specified minimum tensile capacity of the corresponding bolts and threaded rod, the connection point does not become the weak link in a threaded rod assembly.
• American-made construction from a trusted structural brand - produced in the United States and backed by Simpson's reputation in structural connector engineering, this coupler nut is a dependable choice for rod splicing and anchor bolt connections where performance cannot be compromised.

Specifications

• Manufacturer Part Number (MPN): CNW3/4-3/4-OST
• Brand: Simpson Strong-Tie
• Rod Diameter: 3/4 in. to 3/4 in.
• Height (Min.): 1-3/4 in.
• Thread Type: One side oversized (OST)
• Finish / Coating: Zinc Plated or Uncoated
• Country of Origin: United States

Approved Applications

• Connecting threaded rods to one another in structural applications
• Connecting threaded rods to anchor bolts
• Use with hot-dip galvanized bolts where oversized thread clearance is required

• 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

What is the purpose of the Witness hole on this coupler nut?

The Witness hole provides a visual means to verify that each threaded rod is properly and fully installed. When tightening the two rods, you should tighten them until each all-thread rod is visible through the Witness hole, confirming correct thread engagement before load is applied.

What does "OST" mean, and how do I identify the oversized end of this coupler nut?

OST stands for Oversized Thread. This coupler nut features oversized threads on one end only, which allows it to be installed onto hot-dip galvanized bolts. The oversized side of the nut is marked with an "O" so it can be easily identified during installation.

What rod diameter is this coupler nut designed for, and what is its minimum height?

This coupler nut is designed for a rod diameter of 3/4 in. on both ends, with one end featuring oversized threads. The minimum height of the nut is 1-3/4 in.

What finish options are available for this coupler nut?

The CNW3/4-3/4-OST coupler nut is available in Zinc Plated or Uncoated finish. Note that the oversized thread end is specifically designed for use with hot-dip galvanized bolts, such as the SSTB-HDG anchor bolt.