Homemade milling spindle

[rayh__]

Thanks, I am definitely working on the camera work. About the square shaft: I have done a 3D CAD-simulation with torque applied to the shaft, up to 30 Nm of torque the shaft shows no problems at all. I calculated the (350 Watts)motor torque to be 2,4Nm, nominal. A 1:3 transmision results in 7,2Nm at the shaft, not including startup torque (which will be low as the milling cutter normally doesn't touch the work on startup). Conclusion: a safety factor of aproximately 4. The included image shows the simulation with 30Nm of torque on the shaft.

The issue is not whether or not the square shaft will handle the torque. The issue is that the light interference fit between the lower quill and the upper stub (square) shaft will not. Your FEA is looking at the wrong area. The problem will become obvious once you attempt to drill 1/2" diameter hole through 1/2" thick steel.