Position the ball nut on the ball screw shaft.
Using wooden dowels that have an O.D. comparable to the diameter of the ball bearings, center the ball nut grooves with the shaft grooves by inserting dowels into each of the ball nut return circuit holes.
Remove the second dowel from one end, having the ball return holes up, then fill the circuit with ball bearings.
Then turning the screw in the ball nut will aid in feeding the ball bearings into the groove.
When the circuit(s) is full, the balls will begin to lift the end dowel from its position.
To ensure the circuit is full, lightly tap the top ball bearing and check to see if the end dowel moves.
Fill the return tubes with ball bearings until there is a 4 or 5 ball space in the return tube.
Replace top of return tube.