Bolted Connections with Varied Hole Diameters

The effect of oversize holes on the slip resistance and ultimate strength of bolted joints is evaluated. Tests were performed on 47 different lap and butt joints. The average slip coefficient of the friction-type butt or lap joint using 3/4 in. and 7/8-in. A325 high-strength bolts was not signficantly reduced with an oversize up to 3/16 in. when a washer is placed under the turned element. When the oversize was increased to 1/4 in. the bolthead had very little contact with the plate and it was difficult to obtain the minimum tension in the bolt. The ultimate shear strength of the bearing-type butt or lap joint using 3/4 in. and 7/8-in. A325 high-strength bolts was not reduced by any significant amount with an oversize of upt o 3/16 in. Upon increasing hte oversize to 1/4 in., the boltheads cut into the plate to such a great extent that the heads almost pulled through the holes.