My rough FEA model is shown below. I'm pushing on the tool in the x and z directions (y and z on the model coordinates - it got turned around a bit). The color shading shows deflection and the scale is in meters. I find it easier to work in metric units in fea but design everything in inches. The deflection is autoscaled which means that it's not to scale. It's exaggerated so you can see where it's moving. So in this design, the tip of the 1" endmill is moving about 0.008" under a 400lbf load and in both the y and -z directions plus the effect of gravity. I should also point out that this model uses symmetry, so while only half the machine is shown, there's a plane of symmetry included in the model so the results are the same as if the entire thing was there. This is done to make the model solve faster (or at all given the limitations of my computer). The limitation is that I can only apply loads that are symmetric or make sense as symmetric loads, so I can't apply a load in the x direction for example.