The Relationship Between The Tightening Torque And The Clamp Force

Screw fasteners used in the assembly of microwave filters were subjected to tensile and torque tests to determine their yield strengths and the torque that can safely be applied during the assembly process. 2-56, 4-40, 6-32, and 8-32 screws with or without nylok and silver plate finish were tested in the project. Special holders were manufactured for the tensile tests. The torque tests utilized a rotary torque transducer attached to a display unit and a load cell washer. The results obtained show that the published yield and tensile strengths of the screws are quite conservative. The clamping forces generated in the screws were well below the yield strength of the screws. The nut factor in the torque formula decreased with the nylok and silver finish and thus increased the clamping force.