To receive a cutting burr, which may include a loading and working position, the surgical device having a locking mechanism. The locking mechanism locks the cutting burr in place, the cutting burr, when in its loading position, to prevent falling out inadvertently from the surgical drill instrument carries a locking pawl and a detent pawl it may include a motor drive spindle. Diamond-shaped portion of the cutting burr may be formed in the six sides diamond configuration and vertical rear end surface. The ends of the cutting burr, meshes with a complementary surface formed on the receiving end of a spindle of the motor / locking mechanism may include another diamond-shaped portion formed by six sides diamond shaped surface. In one embodiment, the attachment of the cutting burrs, cutting burr is such as to accurately operate under operating conditions.