Sun gear doesn't fit on shaft

I’m trying to fit http://www.andymark.com/product-p/am-0040.htm on http://www.andymark.com/product-p/am-0912.htm and it’s not working. We already went through a motor. It doesn’t fit smoothly. Am I doing something wrong?

These two items are designed to be pressed together. It takes even pressure directly along the motor shaft axis to do it. Many options are available to do this. An Arbor press or a vice make if fairly easy. The key is to keep everything in a perfectly straight line. Any off axis pressure is going to bend your motor shaft. Make sure you are supporting the back side of the motor shaft against the vice.

See this thread: