In the accompanying illustration 1, 2 and 3 represent twist-drills of three sizes and the corresponding reamers for the manufacture of bone nails; 4 is a chuck to receive the drills, and 5 the spindle which receives not only the chuck but the reamer as well. These reamers have a slightly wider diameter on the inner side at the base than they have at the cutting end; preventing any binding or twisting of the nail. In obtaining the nails it is advisable to utilize the bones removed from the groove, or at least to make them in the long diameter of the bone if no groove is made. When made in this manner the nail is far stronger than when made transversely.
Of course, these instruments are operated by means of an electric motor and we find one with a friction-driven shaft less apt to bind and more even in