20) For a bolt of diameter d and length > 150 mm, its thread length is calculated as

21) The type of rivet mostly used in shipbuilding is

22) For a given thickness t of plates in a single rivet butt joint, the thickness of single cover plate is calculated as

23) The type of screw thread form used for motion and power transmission is

24) The joint used to connect the rods of square or rectangular cross-sections, subjected to axial forces is called