Drop In Anchors

Drop In Anchors are internally threaded, deformation-controlled expansion anchors with a pre-assembled expander plug. They are ideal for flush mount application in solid base material and for securing transformers and meters, ceiling fans, cable trays, pipe hanging and electrical light fixtures.

The anchors are available in three materials:

  • Carbon steel, zinc plated
  • 304 stainless steel
  • 316 stainless steel

The anchors are preassembled for ease of installation. They feature female threads that accept standard UNC bolts or threaded rods from ¼-inch to ¾-inch. The slotted body is precision-matched to tapered internal plug to ensure uniform expansion. They also include a knurled body to increase frictional forces between the anchor and the wall of the hole.

There are four variations of the anchor:

  • Steel drop in with smooth wall
  • Steel drop in with flanged/lipped design
  • Shorty Fixed Depth Lipped Drop In Anchor
  • Coil-thread

A drop in setting tool is necessary to ensure proper installation.

Steel Drop In Anchor With Smooth Wall

This variety of the drop in anchor includes internal threads, deformation-controlled expansion with a preassembled expander plug for a flush mount.

Steel Drop In Flanged/Lipped Anchor

This particular variation of the drop in anchor includes a lip at its top that assists in keeping the top of the anchor flush with the concrete. It eliminates the need for precise drilling of the hole depth and allows for easy flush installation and consistent embedment.

Shorty Short Fixed Depth Lipped Drop In Anchor

These anchors are ideal for use in solid and hollow concrete. The short length permits a shallow embedment that assists in avoiding drilling into rebar or prestressed strands. The wide surface flange allows the short drop in anchor to be installed in any type of hole.

Coil Thread Drop In Anchor

Drop in anchors are also offered in coil-threaded for ½-inch and ¾-inch coil threaded rods. This particular anchor works the same mechanically as a regular drop in anchor.

Technical Specifications

Before using a concrete drop in anchor, there are certain facts that should be considered. These include:

  • The diameter and material of the anchor
  • The internal thread length
  • Minimum edge distance
  • Required hole size

This anchor is an ideal fastener for working with flush mounting applications. The size of the drop in anchor refers to the diameter of the standard UNC threaded rod or bolt to be used with the fastener.


Length is an important consideration when setting the anchor with the base material. To determine the minimum bolt length required for an application, add the internal thread length of the anchor, plus the thickness of the material to be fastened, plus the thickness of any washer to be used.

When setting the anchor deeper into concrete you will need to determine the minimum bolt length above and add the additional depth to the minimum anchor length.


The forces of a drop in anchor are transferred to the material in which it is installed. You don’t want the anchors installed too close together because there could be an interaction of the forces causing a reduction of their holding power. Minimum anchor spacing and minimum edge distances for the drop in anchor should follow these parameters.

Anchor Diameter: ¼-inch
Spacing Between Anchors: 3-1/2-inches
Minimum Edge Distance: 1-3/4-inches

Anchor Diameter: 3/8-inch
Spacing Between Anchors: 5-11/16-inches
Minimum Edge Distance: 2-13/16-inches

Anchor Diameter: ½-inch
Spacing Between Anchors: 7-inches
Minimum Edge Distance: 3-1/2-inches

Anchor Diameter: 5/8-inch
Spacing Between Anchors: 8-5/16-inches
Minimum Edge Distance: 4-1/8-inches

Anchor Diameter: ¾-inch
Spacing Between Anchors: 10-1/2-inches
Minimum Edge Distance: 5-1/4-inches

Spacing should be increased when vibration or sudden impact are part of the load conditions.


Items you will need to install a drop in anchor include:

  • Hammer Drill
  • Drill Bit
  • Hammer
  • Wrench
  • Vacuum
  • Drop In Anchor
  • Setting Tool
  • Threaded Bolt

The installation can be achieved in nine steps.

  1. Adjust the depth of the drill bit on the hammer drill. If the hammer drill does not have a depth adjustment, place a piece of masking tape at the point where you need to stop drilling.
  2. Set the hammer drill to hammer mode.
  3. Select the proper drill bit size. A ¼-inch drop in anchor needs a hole that is 3/8-inch in diameter. If you make the hole about 1/8-inch or 1/16-inch larger than the diameter of the drop in anchor, it should fit securely.
  4. Place the hammer drill perpendicular to the point where you want to drill the hole.
  5. Drill the hold to the proper depth and withdraw the hammer drill.
  6. Use the vacuum to clean out all the dust and debris in the hole.  For a drop in anchor to fit properly, it is essential that you remove as much dust and debris as possible.
  7. Place the drop in anchor into the hole. If there is a problem fitting the anchor into the hole, then remove the anchor and vacuum the hole again. Make certain that the top of the anchor is flush with the top of the slab.
  8. Insert the setting tool into the hole on top of the anchor.
  9. Strike the setting tool with the hammer until the lip of the setting tool comes in contact with the lip of the anchor. This ensures that the anchor is correctly set into the cement.
  10.  Attach fixture and threaded bolt to secure to the cement slab.
  11. Thread the threaded bolt into the anchor and tighten with a wrench.

Determining the proper fastener to use for a particular application can be daunting. The staff at AbraFast is well versed in what and how to use fasteners in construction applications. If you have any questions, give us a call at 630-882-9010.