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.
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.
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 Diameter||Threads Per Inch|
|Drop-In Anchor Diameter||Lengh of Drop-In Anchor|
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 Diameter||Hole Diameter|
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.
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.
As 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.