[midgetracer]

Tap the inside of the tube with a 5/8 inch fine thread tap. No need to drill the shaft as a 5/8 inch tap will work with no further sizing. Then use a 5/8 fine thread grade 8 bolt and a stack of washers, and with the tube securely clamped in a vise, use an impact wrench to force the worm unto the shaft. Of course, you must align the worm splines with the grooves on the shaft. I have done many this way and it avoids bending the shaft. To remove the worm without damage to the shaft, I use a bearing puller and put the device in the press and push the shaft off with a properly sized bolt on the end of the shaft with the worm attached. Good Luck