Abstract: A system for fastening a head stack to a hard drive base assembly (HDBA) comprises a threaded head stack pivot (THSP) having a socket defined therein. The socket comprises a proximal portion defined by inner walls arranged parallel to a longitudinal axis of the socket and a distal portion having a width less than a width of the proximal portion and forming a ledge adjacent to the proximal portion. The system also comprises a bit for driving the THSP into an HDBA. The bit comprises a head comprising contact surfaces arranged parallel to a longitudinal axis of the bit and tapered surfaces extending from respective contact surfaces to a distal end of the bit. The bit is configured to engage the ledge at seams formed between adjacent tapered surfaces and to engage the inner walls with respective contact surfaces when driving the THSP into the HDBA.