Are ASSY self-tapping screws considered “full-body” fasteners?

Full body fasteners have a shank diameter that is equal to the outside thread diameter of the threaded portion.
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When self tapping screws are manufactured, the thread rolling process produces an outside thread diameter greater than the shank diameter, which in turn is greater than the minor (or “root”) diameter.

Since the outside thread diameter is larger than the shank diameter, holes in steel plates need to be sized to accommodate the outside thread diameter (while for full-body fasteners like lag screws, the hole is sized to the shank diameter). Kombi screws have a tapered shoulder underneath the head which is equal to the outside thread diameter to provide sufficient bearing against steel plates, which makes them especially suitable for steel to wood connections.

With regards to which diameter size to use in the Yield Limit Equations as specified in NDS 2018, (Cl., more information can be found in the technical article, Which Diameter Do I Enter in the Yield Model Equations?

Relevant Technical Resources

Gallery canadian screw design guide cover Canadian Structural Screw Design Guide
Gallery dg   assy fastener catalog cover American Structural Screw Design Guide

Products Covered in this Article

Gallery assy eco explosion resized ASSY Eco Countersunk Head
Gallery eco a2 ASSY Eco Stainless Steel
Gallery assy kombi explosion resized ASSY Kombi
Gallery kombi a2 ASSY Kombi Stainless Steel
Gallery sk a2 ASSY SK Stainless Steel
Gallery assy sk explosion resized ASSY SK Washer Head
Gallery assy vg csk explosion resized ASSY VG CSK Counter Sunk Head
Gallery assy vg cyl explosion resized ASSY VG CYL Cylinder Head
Gallery assy vg rh explosion ASSY VG RH Reverse Head

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