A construction toy set includes a plurality of interconnectable toy set elements such as couplers for beams which define respective sockets or bores therein. A pin connector defines a generally cylindrical collar supporting a pair of outwardly extending oppositely directed generally cylindrical pins which are receivable within the bores and sockets of the construction toy elements. The pins of the pin connectors each define an elongated expansion groove and an elongated rib extending substantially the length of the pins. The expansion grooves and ribs deform due to the resilient plastic material of the pin during pin insertion into the cooperating bores and/or sockets of the construction toy elements to allow the pins to deform and provide a snug but pivotable fit therebetween.