A surgical device for applying a plurality of surgical staples is provided. The device includes a staple fastening assembly attached to a surgical instrument. The staple fastening assembly includes a pair of cooperating jaws, a jaw operating mechanism, and a gap sensor. A staple magazine having a plurality of staples and an anvil member having a plurality of staple pockets are attached to the jaws. The staple magazine includes a staple crimping cam and a staple dimpling cam that are operatively coupled to the surgical instrument. The jaw operating mechanism is operatively connected to a drive assembly in the surgical instrument for moving the jaws for automatically setting a tissue gap between the cooperating jaws. The gap sensor cooperates with the jaw operating mechanism for controlling staple formation.