The Hilti Drop-In referred to as an HDI, is an anchor manufactured and sold by Hilti, Inc. The Hilti drop-in anchor is a female anchor which in an internally threaded, flush mounted expansion anchor designed for use in solid concrete only. The standard HDI is made from carbon steel and then zinc plated. It is also available in 303 stainless steel. The HDI is manufactured with standard national coarse threads in five diameters- 1/4", 3/8", 1/2", 5/8" and 3/4" diameters.
Other versions of the HDI for specific applications are available. The HDI-P is a short version of the HDI which is available in the 3/8" diameter only. The HDI-P is designed for use in hollow-precast and post-tensioned concrete. The HDI-S, which is only available in the 1/2" diameter, has internal coil threads and is used in concrete forming applications where coil rod is used. The HDI-L has a lip on the threaded end that allows for consistent anchor embedment and rod alignment.
Each diameter is available in one length and all need to be set with a setting tool that is purchased separately. The setting tool most commonly is the hand setting tool. The 3/8" and 1/2" diameters have an automatic setting tool that fits into a hammer drill so that the drill can be used to set the anchor.
The HDI is mainly used in applications for hanging pipe, trapeze and electrical conduit from concrete ceilings. The hole to be drilled in the concrete must be larger than the designated diameter of the HDI since the designated diameter refers to the inside diameter of the HDI.
HDI anchors can be installed in four simple steps. It is important that a hammer drill is used for drilling the hole in the concrete base material. The hammer drill is used in conjunction with the properly sized carbide bit that will make the best hole, which is essential since hole and anchor sizes are critical.
1. Adjust the depth gauge or put tape on the drill bit to measure the HDI drop-in anchor so that once the hole is drilled, the anchor will be flush with the surface of the concrete.
2. Using a hammer drill in the hammer & drill mode, drill the hole in the concrete making sure the hole depth is equal to the length of the HDI being used.
3. Use a wire brush, compressed air or vacuum to clean the hole of all debris.
4. Drop the HDI drop-in anchor into the hole that you drilled in the concrete in Step #2. Using the correct setting tool for the diameter of the anchor being used, drive the setting tool with a hammer until the shoulder of the setting tool meets the shoulder of the HDI drop-in anchor. Now the HDI anchor will be correctly set.
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.