Does anyone have any formulas that will calculate approximate side loads on a cutter i.e. given feed rate, rpm, chip load, and material etc.?
There are SOOOOO many variables......It is really more practical to follow manufacturer recommended feeds, DOC, chip loads, and speeds.
Just the helix angle alone can change the number by 50%.
If you wanted to be really ambitious, you could put a fish scale type force gage in your mill, linked between the spindle and table, gradually move the table with the pulse generator away and watch the gage display, meanwhile watching the load on the table's stepper. A series of measurements would give you an actual curve of force vs. stepper current.
Once you have that curve, you can put the mill in question in the spindle, and start taking some cuts in the mat'l in question with known variables and get some real empirical answers. You could even derive your own equations.
Me? I've just learned how to not break stuff. (at least not all the time)