A supply reel hub (16) for use on a computer tape drive (10) for assuring that a supply reel (12) is squarely locked down and properly aligned on the computer tape drive (10). The supply hub (16) comprises a locking means in the form of three L-shaped feet (20) for locking the supply reel (12) securely in place, a plurality of spaced apart sensing means (52) and a plurality of signalling means (56,58,60) which sense and signal to a control­ler (142) whether each of the three L-shaped feet (20) of the locking means (64,66,68) are properly in position. A centering knob (28) positioned on the top of the supply hub (16) has been provided so that a supply reel (12) may be easily centered over the supply hub (16). A groove is positioned on the base of the supply hub (16) to allow a write enable tab to slip off of the supply hub (16) and not hang up on the centering knob (28). Additional sensing means (62,78,86) are provided for sensing whether there is a write enable ring on the supply reel (12). Means for releasably attaching the shaft (24) of the drive motor (27) to the hub base which reduces tape edge damage is also provided. The positioning of the L-shaped feet (20) is checked on loading and unloading and in the event of improper positioning of the L-shaped feet (20), an error message is displayed on the computer tape drive (10) and may also be displayed on the computer. A method of assuring the locking and unlocking of the hub (16) is also disclosed.