The Maxi-Bolt Undercut Anchor System

Developed in 1980, the Maxi-Bolt was the first practical undercut anchor. Since that time the Maxi-Bolt has been used in thousands of demanding applications - applications in which a typical sleeve or wedge anchor would have been out of the question. Because of its unique undercut design, the Maxi-Bolt anchor is the functional equivalent of a cast-in-place anchor. Unlike grouted and epoxy anchors, the Maxi-Bolt retains its holding capacity even in cracked concrete. If you have an application involving high design strength requirements, dynamic loading or the possibility of a cracked concrete environment, the Drillco Maxi-Bolt Undercut Anchor is the bolt for you.

In many applications, oil-soaked concrete prevents the use of grouted or epoxy anchors. The Maxi-Bolt works well in these environments because it derives it holding power from mechanical interlock - not chemical bonding.



Application Tip: In many cases the concrete in industrial plants has become soaked with oil. Adhesive and grouted anchors will not bond properly to this concrete. Maxi-Bolts, on the other hand, work fine in these situations.

Legal Disclaimer: The design information presented here applies only to Drillco Maxi-Bolts. Because dimensional characteristics particular to the Maxi-Bolt are hard-wired into the design calculations, Drillco can make no representation as to their validity when applied to other undercut or cast-in place anchors.

Notice: Unless otherwise noted, all load and design values presented herein are based on the provisions of ACI 349-97 or earlier. Design guidance based on ACI 318-05 and ACI 349-06 is being prepared and will appear here shortly. In the mean time you may wish to review the results of cracked concrete testing performed in accordance with ACI 355.2 as called for in the new codes.

  • Quick Reference Load, Spacing and Torque Tables from ICBO Evaluation Report 4133.
  • Tension and Shear Load Allowables and Embedment and Spacing Tables for all available materials.
  • An Undercut hole is the secret of the Maxi-Bolt's superior performance.
  • Features and advantages of the Maxi-Bolt
  • The Maxi-Bolt is manufactured under a rigorous quality assurance program.
  • General Design Considerations.
  • ICBO Evaluation Report 4133
  • Calculating Projected Concrete Area to Determine Concrete Pullout Capacity.
  • Appendix B of ACI 349, "Steel Embedments"
  • Test Data and Reports
  • Materials

  • Available materials
  • Installation

  • Maxi-Bolt installation videos.
  • Animated installation sequence. (610 kB)
  • Maxi-Bolt installation outline.
  • Detailed Maxi-Bolt installation procedure.
  • Detailed Maxi-Bolt installation procedure. Printable version in PDF Format
  • Stud-Type Anchor Installation. (Slide Show Format)
  • Flush-Type Anchor Installation. (Slide Show Format)
  • Flush Mount Maxi-Bolt

  • The Flush-Mount version of the Maxi-Bolt
  • Detailed Maxi-Bolt Flush-Mount installation procedure.
  • Anchor Bolt Removal

  • Anchor Bolt Removal System.
  • Part Numbers

  • Part Numbering System for Maxi-Bolt Anchors, Drill Bits, Tooling and Accessories
  • Calculating required bolt length when embedment depth and attachment thickness are known.
  • Part Numbers for Available Installation Kits
  • Large Diameter Maxi-Bolts

  • Drillco Now Makes Big Bolts - Up To 6" Diameter
  • Jobsite Photos

  • Examples of Maxi-Bolt use on Steam Generator Retrofits, Combined Cycle Plants, Electrical Generator Replacements, Electrical Substations, Moveable Bridges, Seismic Retrofits on Bridges, Can Forming Equipment and Petro-Chemical Sites.

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