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Simpson Drop-in Anchors

  • Monday, June 30, 2008

    Purchase Drop-In Anchors

    Drop-In Internally-Threaded Expansion Shell Anchor

    Drop-In anchors have internal threads and an expansion of the anchor called deformation-controlled. The drop-in anchor is considered a shell anchor because it is expanded from the inside out using the expander plug and a setting tool. Simpson Strong-Tie anchor systems at drop-in anchors are available with the expander plug pre-assembled and are designed for use in concrete only.

    Drop-In (DIA) Material Specifications

    The Drop-in anchor from Simpson is available in three materials. One is the standard zinc plated carbon steel with a minimum tensile strength of 70,000 psi for the anchor body and with the expander plug that meets minimum tensile strength of 50,000 psi. The second type is the 303 stainless steel drop-in that meets AISI 303 requirements for the anchor body and the expander plug. The third type is the 316 stainless steel Simpson drop-in anchor which meets requirements for 316 stainless steel.

    Drop-In Testing Criteria

    Simpson Strong-Ties drop-in anchors have been tested in accordance with the ICC-ES’s criteria for expansion anchors (AC01) for seismic/wind loads, combination loads in tension and shear and minimum spacing and edge distance.

    Drop-In Anchor Codes

    Simpson Drop-in anchors meet the following codes:

    1. Meets Federal Specification Requirements A-A-55614, Type 1
    2. Factory Mutual 3017082
    3. U.L. File Ex3605
    4. City of L.A. RR24682

    Diameters of Drop-in Anchors

    Drop-in anchors from Simpson Strong-Tie come in five diameters: 1/4”, 3/8”, 1/2”, 5/8” and 3/4” in the standard carbon steel, 303 stainless steel, and 316 stainless steel.

    Simpson Drop-in Anchor Lengths

    Each diameter of drop-in anchors is manufactured in one length. The 1/4” drop-in anchor is 1” long, 3/8” is 1-1/2” long, 1/2” is 2” long, 5/8” is 2-1/2” long and the 3/4” is 3-1/8” long.

    DIA Thread Diameter

    The Simpson Strong-Tie drop-in anchor anchors are designated by the diameter of the internal threads. All of the threads on the drop-in anchor are national coarse threads, which means any bolt or threaded rod that has the same threads can be threaded into the drop-in anchor. National coarse threads are measured by how many threads are in a distance of 1”. The 1/4” drop-in has 20 threads per inch, the 3/8” has 16 threads per inch, the 1/2” has 13 threads per inch, the 5/8” has 11 threads per inch and the 3/4” has 10 threads per inch.

    Hole Diameter

    The hole diameter of the drop-in anchor is equal to the outside diameter of the anchor and is larger than the designated diameter of the anchor. All drop-in anchors are designated with the inside diameter threads. The outside diameter is larger and is equal to the diameter of the hole that must be drilled in the concrete. The 1/4” drop-in anchor requires a 3/8” hole, the 3/8” requires a 1/2” hole, the 1/2” requires a 5/8” hole, the 5/8” requires a 7/8” hole and the 3/4” drop-in requires a 1” hole. The hole must be drilled with a hammer drill and a carbide bit that meets ANSI standards which will ensure properly matched tolerance between the anchor and the hole.

    Drop-In Embedment Depth

    Each diameter of drop-in anchor must be placed into the concrete a minimum of the anchor length so that the anchor sits flush with the surface of the base material. Drop-In anchors can be placed in the concrete at deeper embedment, which in most cases will allow for improved holding values. Deeper embedment would require a longer bolt or threaded rod length to accommodate the deeper embedment.

    Installation Tools for Drop-in Anchors

    The drop-in anchor should be set into the concrete once it has been inserted into the pre-drilled hole in the concrete. Each diameter of the drop-in anchor has a corresponding setting tool that must be used to ensure that the drop-in anchor is expanded fully and properly. The drop-in anchor is properly set when the shoulder of the setting tool contacts the anchor body.

    Drop-In Anchor Installation Instructions

    1. Using a hammer drill, drill a hole in the concrete with the correct diameter of carbide bit for the diameter of the drop-in anchor being installed. For a flush surface mount installation, make sure that the hole is drilled 1/8” deeper than the planned embedment depth of the anchor. Use an ANSI standard carbide tipped bit because an oversized hole will make it hard to set the anchor and will reduce the drop-in anchor's load capacity.
    2. Clean out the hole with compressed air.
    3. Place drop-in anchor into the hole, non-threaded end first, and tap lightly with a hammer until the anchor is flush with the surface of the concrete.
    4. Insert correct setting tool for the diameter of the drop-in anchor being installed into the threaded end of the drop-in anchor, and strike with a hammer until the lip of the setting tool touches the shoulder of the drop-in anchor.

    Drop-In Anchor (DIA) Product Information

    Diameter of Anchor

    Carbon Steel Drop-in Part #

    303 Stainless Steel Part #

    316 Stainless Steel Part #

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    Purchase Drop-In Anchors


    Always use personal protective equipmentAs with any anchoring project, it is important to keep safety in mind and follow instructions carefully. Always remember to wear safety goggles, handle all tools with extra care and follow all technical specifications. This article is meant to serve only as a basic explanation of concrete fasteners. Always refer to manufacturer's instructions or consult a contracting expert during any anchoring project.

    Article Written By:
    Mike Pistorino, Vice-President Operations





    Concrete Fasteners, Inc. has over 40 years of experience selling concrete fasteners. We can ship out one box or a whole pallet of concrete anchors. Our products are of the highest quality... "your satisfaction is guaranteed". We ship all orders the same day the order is received.

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