calculating a rough estimate for bearing dynamic/static load

I've read through the FAQs and can't seem to figure out how to calculate the static and dynamic load that my bearing assembly might experience. There are various calculators on the web, but I have NO idea how to figure out the various values. :confused: <= me

Here is the situation.. i've got a turned ballscrew, I have a ~17mm length of diameter 8mm, onto which I want to sandwich 2 angular contact bearings housed in a bearing block.

The problem is, I can find only one supplier that has bearings of this ID, which is alpinebearing. The static/dynamic load rating is 220/560 lbs, or 270/706. Wow, sounds like a decent amount?

Well maybe not, just for kicks I looked at their "Ball screw support" bearing ratings for the 17mm ID unit. the rating on those: 5600/5600. Furthermore, SKF has single AC bearings of 10mm ID with a static load rating of 11.2kN, which is around 2500lbs.

Any advice/suggestions? (other than to go back to school and study mechanical engineering)