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Maxi-Bolt Anchor

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.

  • Quick Reference Load, Spacing and Torque Tables from ICC ESR 3029

  • Building Code & Engineering Approvals

  • 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.

  • ICC ESR 3029

  • Calculating Projected Concrete Area to Determine Concrete Pullout Capacity.

  • Appendix B of ACI 349, "Steel Embedments"

  • Test Data and Reports


  • Available materials


  • Maxi-Bolt installation videos.

  • Animated installation sequence.

  • 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

  • Case Study in the Use of Very Large Diameter Maxi-Bolts

See a few examples from the hundreds of demanding applications in which the Maxi-Bolt has been used.

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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