Print the file HalfInchReel.stl. This prints the base half of the reel including the hub. If you're running this horizontally, you don't really need the other half. For a complete reel, next print HalfInchReelTop.stl. Then glue the two pieces together, making sure the tape threading notches in the hub line up.
The scad source is provided for your modding pleasure. If you want to print a small sample to test the calibration of the critical central part, set the variable "basediameter" to 50. The source can also be easily modified to make a 7" reel, or a reel for 1/4" audio tape.