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American Made Drop-in Anchor

Thursday, January 27, 2011
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Purchase Drop-In Anchors

Applications for Drop-In Anchors

The drop-in anchor is designed for use in solid concrete and cannot be used in base materials such as brick or CMU (block). The drop-in anchor is primarily used for threading threaded rod and hanging electrical conduit, pipe or ventilation duct work from the threaded rod. Drop-in anchors are also used as a female type concrete anchor in conjunction with a threaded bolt that allows bolting and unbolting of the item being fastened. The drop-in anchor sits flush with the surface of the concrete and, once the bolt is removed, there is no tripping hazard.

Types of Drop-in Anchors

Two types of American made drop-in zinc plated carbon steel and the 303 stainless steel are currently being manufactured. Special runs to make the drop-in anchors using 316 stainless steel are possible, but, at this point, 316 stainless steel drop-in anchors are not manufactured for inventory.


The five standard diameters 1/4”, 3/8”, 1/2”, 5/8” and 3/4” drop-in anchors are being produced in both the zinc plated carbon steel and stainless steel.

Internal Threads on Drop-In Anchors

The internal threads of the drop-in anchor are national coarse threads and receive any type of threaded item with the same national coarse threads. The internal threads equal about half the length of the total length of the drop-in anchor.

Drop-In Anchor DiameterThreads Per Inch
1/4" 20
3/8" 16
1/2" 13
5/8" 11
3/4" 10

Length of Drop-In Anchors

Drop-In Anchor DiameterLengh of Drop-In Anchor
1/4" 1"
3/8" 1-*9/16"
1/2" 2"
5/8" 2-1/2
3/4" 3-1/8"

Hole Diameter

The diameter of the hole that needs to be drilled is equal to the outside diameter of the drop-in anchor. The designated size of a drop-in anchor refers to the inside diameter or the diameter of the threaded rod or bolt that threads into it.

Drop-In Anchor DiameterHole Diameter
1/4" 3/8"
3/8" 1/2"
1/2" 5/8"
5/8" 3/4"
3/4" 1"

Depth of Hole

In most applications using drop-in anchors, the drop-in anchor must sit flush with the surface of the concrete. For the drop-in anchor to sit flush with the surface, the depth of the hole must be equal to the length of the drop-in anchor being used. The proper depth can be achieved by using the depth gauge on the hammer drill or by placing tape on the bit at the desired drill depth.

Setting the Drop-In Anchor

The drop-in anchor requires a setting tool to be used to set the anchor once it is placed in the hole in the concrete. Each diameter has a matching setting tool that must be correctly used to ensure that the drop-in anchor will obtain holding values required. The setting tool is a rod of steel manufactured so that the lip of the setting tool touches the lip of the drop-in anchor to fully set the drop-in anchor.

Drop-In Anchors Installation Instructions

  1. Drill a hole in the concrete using a hammer drill, with the correct diameter ANSI standard carbide tipped bit, to a depth that equals the length of the diameter of the drop-in anchor being installed.
  2. Clean out the hole in the concrete of all dust created during the drilling process using a wire brush, compressed air, and vacuum.
  3. Place drop-in anchor with the threaded end up towards the surface of the concrete into the hole in the concrete.
  4. Insert the correct drop-in setting tool into the threaded part of the anchor, then use a hammer to strike the setting tool with hard sharp blows until the lip of the setting tool touches the lip of the drop-in anchor.
  5. The drop-in anchor is now properly set, and a bolt or threaded rod can now be threaded into the anchor.

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 Fastening Systems, 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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