What kinds of stress and forces (axial, Radial, compression, etc.) do I need to keep in mind when designing a Mill?
Having recently designed and built a mill myself might I offer this... Design the mill around the spindle you choose. It's important to determine what you intend to do with the mill. That is, milling aluminum, wood, plastic will help you ascertain the power needed. Is it a desktop mill or freestanding floor model. I'll be more than happy to help in any way I can if you need any assistance.
There are many out there. Again, it boils down to what you prefer based on what you wish to do ...water cooled, air cooled, VFD a/c, PWM dc's. Bear in mind it's really easy to spend thousands when constructing a mill. I use a TB-650 from Wolfgang Engineering ($250) on my desktop mill, and 2.2kv water cooled w/ VFD ($700) on my shop mill. For my purpose, there have been no material limitations with either. I'm not boring engine blocks, but small mild steel parts on my desktop and facing large billet ingots is not out of the question in my shop.
Thank you very much sir! I have always custom designed my spindles but I also know that there are spindles you can buy. Which would you say is better?