The Simpson HDIA25 HDIA Hollow Drop-In Internally Threaded Anchor is a flush-mount expansion anchor from Simpson Strong-Tie engineered for attaching threaded rod to support conduit, cables, and lighting in a wide range of base materials. Its expansion design performs reliably in both hollow substrates - including CMU and hollow-core plank - and solid materials such as brick, normal-weight concrete, and lightweight concrete, making it a single versatile solution for mechanical, electrical, and fire protection suspension applications.

Key Features

• Expansion anchor design for hollow and solid substrates - anchors securely into CMU, hollow-core plank, brick, normal-weight concrete, and lightweight concrete, so one anchor type covers a broad range of jobsite conditions without swapping products.
• Internally threaded design - accepts a 1/4 in. threaded rod and allows for easy bolt removal, simplifying adjustments, maintenance, and repositioning after installation.
• Flush-mount profile - sits flush with the base material surface, keeping installed surfaces clean and unobstructed for conduit, cable trays, pipe supports, fire sprinklers, and suspended lighting applications.
• Die-cast Zamac 3 alloy shell with carbon-steel cone - combines a corrosion-resistant shell material with a hardened cone for consistent, reliable expansion performance during setting.
• Compatible with dedicated setting tools - installs cleanly using the HDIASTH25 setting tool for hollow materials or the HDIASTS25 for solid materials, ensuring proper seating and full expansion every time.
• 1/4-20 threaded interior with a 3/8 in. drill bit requirement - precisely matched thread pitch and hole size reduce guesswork on the drill floor and help maintain installation accuracy across repetitive anchor placements.

Why This Product

• One anchor, multiple substrates - the expansion design allows this drop-in anchor to perform in both hollow materials like CMU and hollow-core plank and solid materials like brick and concrete, reducing the need to stock multiple anchor types for mixed-substrate projects.
• Built for critical suspension systems - rated for suspending conduit, cable trays, pipe supports, fire sprinklers, and lighting, this anchor is suited for mechanical, electrical, and fire protection trades where secure overhead attachment is non-negotiable.
• Installer-friendly internal threading - the internally threaded barrel makes bolt removal and reinstallation straightforward, which saves time during inspections, system modifications, or any work requiring repeated access to suspended components.
• Engineered material construction - the die-cast Zamac 3 alloy shell paired with a carbon-steel cone delivers a reliable, consistent expansion set that holds firmly once the setting tool drives the cone into position.

Specifications

• MPN: HDIA25
• Brand: Simpson Strong-Tie
• Anchor Type: Hollow Drop-In Internally Threaded Expansion Anchor
• Rod / Bolt Diameter: 1/4 in.
• Length: 3/4 in.
• Drill Bit Diameter: 3/8 in.
• Threads Per Inch (TPI): 20
• Shell Material: Die-cast Zamac 3 alloy
• Cone Material: Carbon steel
• Installation Tool (Hollow Materials): HDIASTH25 setting tool
• Installation Tool (Solid Materials): HDIASTS25 setting tool
• Packaging: Packs of 100 and Cartons of 1600

Approved Applications

• Suspending conduit and cable trays from concrete ceilings
• Pipe support and mechanical system hangers in concrete and masonry
• Fire sprinkler system installations requiring flush-mount anchoring
• Suspended lighting attachment in concrete, CMU, and hollow-core plank
• Anchoring into hollow-core plank and CMU block walls or ceilings
• Threaded rod attachment in brick, normal-weight concrete, and lightweight concrete

Frequently Asked Questions

What base materials is the Simpson HDIA25 anchor compatible with?

The HDIA25 is designed for use in both hollow and solid base materials. Compatible substrates include CMU (concrete masonry unit), hollow-core plank, brick, normal-weight concrete, and lightweight concrete. Its expansion design allows it to grip securely in all of these materials.

What setting tools are required to install the HDIA25?

Installation requires a specific setting tool depending on the base material. Use the HDIASTH25 setting tool for hollow materials such as CMU and hollow-core plank, and the HDIASTS25 setting tool for solid materials such as brick and concrete.

What drill bit size is needed when installing the HDIA25 anchor?

A 3/8-inch diameter drill bit is required to prepare the hole for the HDIA25 anchor prior to installation.

What rod or bolt diameter does the HDIA25 accept?

The HDIA25 is internally threaded to accept a 1/4-inch diameter threaded rod with a thread pitch of 20 threads per inch (TPI). The internally threaded design also allows for easy bolt removal when needed.

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