Using a Vertical Mill as a Chopsaw

A couple weeks back I mentioned the problem of cutting a small slice of an already too small piece of acetal on which to get a safe grip on the chopsaw.  This time, it was a piece of aluminum.  I simplified the process by using the clamps that typically hold the mill vise in place.  (Yes, they are a bit ugly. I made them myself and if I ever need to make another set, they will be prettier.). Fortunately, the piece that I need to hold down is 3/16" thick aluminum.

I aligned the edge of the sheet to the back of the mill table to get it square.  If that edge was not really as square as it should have been, I will fix that in the following step, where I expect to have at least one square edge.

Unlike last time where I was cutting in the Y-axis and had trouble holding it down securely, here I am using T-slot clamps on both sides and cutting on the X-axis where I have more space to move.  The X-axis has more travel than the Y-axis.  (I should have thought about that two weeks ago.)

I am using the smallest end mill that I have confidence (or at least hope) will not break as it cuts.  (5/16"?). I am cutting a .05" deep slice on each pass at .05 inches/minute.  I could perhaps go faster but I feel comfortable letting my robot run unattended at this rate.  It will obviously take several passes to get all the way through a 3/16" sheet of aluminum.

A little too optimistic.  At .005 inches/minute it still had enough resistance to pull the workpiece out of the clamps.  Trying again at .002 ipm.

I just went back to cutting at z=0.  Yes it is more of a scratch than a cut, but it goes .10 ipm.  It might take a lot of passes to do this.  Perhaps a better clamping approach might be a better solution.