Welding Rules of Thumb

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Fillet Welds

A 5/16" fillet is the maximum size for a single pass weld.[1]

The maximum strength of weld is the following:

  • ASD Strength of weld = 0.9 X (# of 1/16ths of throat) X Length
  • LRFD Strength of weld = 1.3 X (# of 1/16ths of throat) X Length

Where: Length is in inches

Weld Sizes

"Typical shop practices have generated a general rule of thumb suggesting that fillet welds are the most cost-effective details for connections requiring throats of 1/2 in. or less, which equates to a leg size of 3/4 in. PJP groove welds are generally the best choice for throat sizes of 3/4 in. or greater. This would roughly equate to a 1-in. fillet weld. In general, fillet welds should not exceed 1-in., nor should PJP groove welds be specified for throat dimensions less than 1/2 in. Between these boundaries, specific shop practices will determine the most economical approach."

- O.W. Blodgett and D. K. Miller[2]

Force Transfer

"...transfer of force takes place from one member, through the weld, to the member that lies parallel to the force that is applied."

- O.W. Blodgett and D. K. Miller (see References)

When joining two steel members: "Provide a path for the force to enter into the member (section) that lies parallel"

- O.W. Blodgett and D. K. Miller[3]


  1. AISC 360-05. pp16.1-331
  2. O.W. Blodgett & D. K. Miller. Structural Engineering Handbook (2001). CRC Press, Inc.
  3. 2008 NASCC Presentation by D. K. Miller


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