Manufacturing

Diverse methodologies are employed to fabricate anchor bolts to suit various requirements. Engineers assess factors such as application and external forces to determine the optimal grade, dimensions, and design swedged anchor rod

The following outlines the different manufacturing processes involved in the manufacture of swedged anchor bolts.

  1. Material Preparation/Cutting:
    Steel round bars, typically 20’ – 40’ long, are cut either by shearing or band sawing. Shearing involves efficient guillotine-like chopping, whereas band saws utilize toothed blades. While shears have diameter and length limitations, band saws offer more versatility.
  2. Thread Formation:
    All galvanized anchor bolts necessitate threaded ends for concrete embedding. Threads can be either cut using chasers or formed through extrusion by two dies. Additionally, straight anchor rods may have threads on the embedded end for pull-out resistance, often accompanied by nuts and/or plates.
  3. Head Formation:
    Some anchor bolts feature forged heads on the embedded end, enhancing pull-out resistance. This process involves heating the unthreaded end to around 2,000 degrees Fahrenheit and shaping it into hexagonal, heavy hexagonal, or square heads.
  4. Bending:
    Galvanized anchor bolts, particularly in smaller, standard sizes, may undergo bending to form a 90-degree hook for embedding in concrete, providing additional pull-out resistance.
  5. Swedging:
    Large dimples or indentations (known as swedging patterns) are pressed into the embedded end of anchor rods, aiding in concrete adhesion and preventing pull-out.
  6. Chamfering:
    A slight bevel is applied to the threaded end to facilitate nut installation, while also removing the first thread to prevent installation issues.
  7. Welding:
    Steel plates and/or pipe sleeves may be welded to anchor rods for various applications, enhancing their functionality and structural integrity.
  8. Plate Fabrication:
    Anchor plates of square, round, or rectangular shapes are often affixed to anchor rods to provide additional pull-out resistance. Steel templates assist in proper anchor bolt spacing during installation.
  9. Heat Treatment:
    Many grades of anchor bolts undergo heat treatment processes to attain specified strength characteristics. Mechanical testing follows to ensure compliance with ASTM specifications.
  10. Galvanizing:
    Hot-dip galvanizing involves immersing anchor bolts in molten zinc to apply a corrosion-resistant coating. Proper zinc removal from threads is crucial, with experienced galvanizers using centrifugal force to spin out excess zinc without affecting the threads.

Swedging Patterns

Portland Bolt offers a “standard pattern” where the space between the dimples is 3” apart if a pattern has not been specified to us. We also offer a spiral pattern where the space between the dimples is 1-1/2” apart. The size and depth of the dimples are listed below.

Standard and Spiral Pattern

Rod DiameterIndentation Size
Under 3/4″As required
3/4″ – 7/8″1/2″ wide x 1/8″ deep
1″ – 3″5/8″ wide x 1/8″ deep

Space between dimples for standard pattern: 3″ Typ.
Space between dimples for spiral pattern: 1-1/2″ Typ. The standard configuration of a swedged anchor rod has thread only on the top protruding from the concrete. A less common configuration is a rod with threads on each end and swedging in the middle