animating on local axis This could be a duplicate question, if so I do apologize for wasting your time. I did some research, but couldn't find the answer for my question. That's why I posted it here. 

I've modeled an Archimedes screw for my undergraduate project. Now i want to incline the setup at an angle of about 30 degrees and add a rotation for this crew. but when I animate the rotation after re positioning, it does not rotate the way I want. It rotates around the global axis, but i want it to rotate around like a screw. what should i do for this ? 

I want my setup to look like this, but when i progrramme the keyframes it does not rotate according to it's new position ( i want it to rotate like a screw)
The simpler method to achieve the result is to animate the screw in vertical position, set the screw to be child of an empty and then tilt the empty 30 degrees (in this way you can even animate the tilt angle).