Frequently Asked Questions
The column heading for NDS® (2001/2005) Table 11.2A states that diameter for determining withdrawal design values is the "unthreaded shank diameter, D." Should withdrawal design values for reduced body diameter lag screws (see NDS Appendix L) be based on the reduced body diameter or the outside thread diameter?
Reduced body and full-body diameter lag screws in accordance with ANSI/ASME B18.6.1 have the same thread dimensions and geometry, and the thread penetration will provide the same withdrawal strength from wood in pounds per inch of thread penetration. Therefore, withdrawal design values are applicable for reduced body and full-body diameter lag screws using the nominal lag screw diameter (outside thread diameter for both types).
Section: Wood Connections and Assemblies