Modifying the HXT12K Servo for Continuous Rotation
1. Remove the four screws holding the case together and take the top cover off.
2. Remove the mechanical stop (small metal pin) either by pulling it out or grinding it off.
3. Remove the bottom cover and pull out the circuit board. Remove the screw holding in the potentiometer and pull it out, then tighten the screw back in place.
4. Plug the servo into a receiver (with transmitter on and trims centered) and adjust the potentiometer's shaft until the motor stops spinning. Glue the shaft in place with hot glue, silicone, or similar. If your servo ever starts turning without being commanded (and adjusting the trims on the radio doesn't help) then you will have to open the servo and recenter this shaft.
5. Push the potentiometer back into the case but not all the way. Make sure it doesn't come past the top of the servo case. Screw the top and bottom covers back on. If you ever need to reverse this modification, simply un-glue the potentiometer and push it back up into the gear (using the screw to hold it in place). The mechanical stop is not required.