Abstract: A coupling member includes a rectangular socket disposed at one end thereof and engaged snugly with the rectangular end of the rotatable rod of a pneumatic tool body, an externally threaded portion disposed at the other end of the coupling member and engaged with the large threaded hole of a drilling head, and a small threaded hole formed in the end surface of the externally threaded portion. When a bolt is passed through the fastener hole of the drilling head to engage with the small threaded hole of the coupling member, the drilling head is secured to the pneumatic tool body. When the assembly of the drilling head and the coupling member is removed from the pneumatic tool body, the rectangular socket of a rotating head can be engaged with the rectangular end of the rotatable rod of the pneumatic tool body, thereby forming a pneumatic wrench.