The Simpson Drop-In Internally Threaded Anchor in Type 303/304 Stainless Steel is an internally threaded expansion anchor designed for flush-mount anchoring in solid concrete base materials. Built to accept a 3/8-in. threaded rod, this drop-in anchor expands securely within the base material to deliver a clean, surface-level finish - making it well suited for overhead, wall, and slab applications where a protruding fastener is not acceptable. Type 303/304 stainless steel construction provides enhanced corrosion resistance, making this anchor a dependable choice for concrete anchoring in environments where standard carbon-steel fasteners may be vulnerable to deterioration.

Key Features

• Flush-mount expansion anchor for concrete applications - the anchor body sits flush with the base material surface, keeping finished surfaces clean and unobstructed.
• Compatible with both hand- and power-setting tools - gives installers flexibility to choose the method that best fits the job, reducing installation time and labor costs.
• Fixed-depth stop bit compatibility - drilling to the correct depth is straightforward and consistent, minimizing the risk of undersetting or oversetting the anchor.
• Designed for 3/8-in. threaded rod connections - accepts standard 3/8-in. UNC threaded rod with 16 TPI, ensuring broad compatibility with common fasteners and hardware.
• Requires a 1/2-in. drill bit for installation - using the specified bit size is critical; oversized holes will make it difficult to set the anchor and will reduce the anchor's load capacity.
• Type 303/304 stainless steel construction - provides corrosion resistance that carbon-steel anchors cannot match, extending service life in demanding or moisture-exposed conditions.

Why This Product

• Flush finish where it counts - the drop-in design expands entirely within the drilled hole, so the installed anchor sits level with the concrete surface. This is ideal for applications where a protruding fastener would interfere with equipment, fixtures, or finished surfaces.
• Corrosion-resistant stainless steel for long-term reliability - manufactured from Type 303/304 stainless steel with an anchor body meeting the chemical requirements of ASTM A582, this anchor holds up in environments where moisture or chemical exposure would degrade standard anchors over time.
• Straightforward installation with widely available tools - hand- and power-setting tools are both compatible, and the fixed-depth stop bit approach removes guesswork from the drilling process, helping contractors and tradespeople work efficiently without sacrificing accuracy.
• Minimum thread engagement guidance protects connection integrity - Simpson specifies that minimum thread engagement should be equal to the nominal diameter of the threaded insert, giving installers a clear benchmark to ensure a secure, properly loaded connection every time.

Specifications

• MPN: DIA37SS
• Material: Type 303/304 Stainless Steel
• Finish: Type 303/304 Stainless Steel
• Bolt/Rod Diameter: 3/8 in.
• Length: 1-9/16 in.
• Thread Length: 5/8 in.
• TPI: 16
• Drill Bit Diameter: 1/2 in.
• Anchor Body Material: AISI 303 - meets chemical requirements of ASTM A582
• Expander Plug Material: AISI 303
• Thread Type: UNC
• Packaging: Packs of 50 and Cartons of 250

Approved Applications

• Flush-mount anchoring in solid concrete base materials
• Applications requiring a 3/8-in. internally threaded rod connection
• Installations where the anchor surface must sit flush with the base material

Frequently Asked Questions

What drill bit diameter is required to install the DIA37SS anchor?

A 1/2-in. drill bit diameter is required for proper installation. Using an oversized hole will make it difficult to set the anchor and will reduce the anchor's load capacity.

What rod or bolt size is compatible with this drop-in anchor?

The DIA37SS is designed for use with a 3/8-in. rod or bolt. Minimum thread engagement should be equal to the nominal diameter of the threaded insert.

What material is this anchor made from, and is it suitable for corrosive environments?

This anchor is manufactured from Type 303/304 stainless steel, with the anchor body meeting the chemical requirements of ASTM A582. The stainless-steel construction provides enhanced resistance to corrosion compared to standard carbon-steel anchors.

What tools are needed to set the DIA37SS drop-in anchor?

Both hand- and power-setting tools are available for installation, allowing for fast, easy, and economical setting. A fixed-depth stop bit is also available to help ensure the hole is drilled to the correct depth every time.

Note: Product dimensions may differ from picture. Please see item description for specifications.