DUC Undercut Anchors Installation Guide

July 20, 2018


A concrete anchor system with a mechanical connection—not a friction-fit

The DUC Undercut Anchor consists of an ASTM A36 or A193 Grade B7 threaded stud, a thick-walled expansion sleeve, an expander coupling, and a nut and washer. All DUC Undercut Anchors are also available in 316 stainless steel versions.


How it Works

The DUC Undercut Anchor is installed into a pre-drilled hole, which has been enlarged at the bottom in the shape of a reversed cone. The reverse cone is created using the USP DUC Undercutting Bit.

The DUC Undercutting Bit fits into SDS or SDS Max rotary hammer drills and guarantees the correct angle of the reverse cone. The anchor is expanded into the reverse cone when the expansion sleeve is driven over the expander coupling. 


The result is an anchor that transfers load mainly through the bearing, and unlike a typical expansion anchor (sleeve, heavy-duty sleeve, wedge, and drop-ins), the DUC is not dependent upon friction between the expansion sleeve and the concrete.

Due to the use of a thick-walled expansion sleeve, the load is distributed to a large area which ensures the ductile behavior of the anchor even at relatively shallow embedments.

The DUC Undercut Anchors have been tested in accordance with ACI 355.2 to be qualified for use with the design methods of ACI 318 appendix.


DUC Undercut Anchor Advantages

Compared with heavy capacity sleeve and expansion anchors and other undercut systems: 

  • DUC Undercut design provides consistent expansion and is easy to set. Stress risers have been eliminated to prevent tearing. 
  • The large bearing area provides exceptional performance even in lower strength concrete. 
  • Load transfers mainly through bearing, not expansion forces and is not dependent upon friction which can be lost when cracks occur. 
  • Thick-walled sleeves transfer load over a larger area which ensures predictable ductile performance. 
  • ASTM A36 or A193 grade B7 rods are used. Full ultimate steel strength of the threaded stud is developed at listed embedment and spacing. Stainless steel is also available. 
  • Installation is simple. It is similar to installing a typical expansion anchor; no coring drills are necessary. The creation of proper undercut is correctly done and easily verified using DUC Undercut Bits. The creation of undercut takes only seconds.

Click here to see our complete line of mechanical anchors.


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Slideshow and download:

InstallDetailDUC Chart.JPG
ReplacementParts Chart.JPG
StopDrillBit Dimensions Chart.JPG
 Undercutter Chart.JPG