Machining Often Involves Making Jigs

One of the parts that I need to machine is a quarter circle, two of which will form the "ears" holding the polar axis assembly.   My goal was 1/4 of a 6" circle. 

Once I started machining the two 3" squares from which was going to cut these pieces, I discovered that because of an arithmetic error I had cut two 2.46" squares.  No matter.  The actual size matters less than roundness. 

I know how to cut half circles in gCode.  Cutting a quarter circle is easy.  But when I do the cut, I need the workpiece above the surface holding it in place to avoid collision.   So how?  Ordinarily, parallels raise a part in the vise but still require the vise to press on the edges of the workpiece.   That will not do because I have to cut through the workpiece. 

I drilled 6-32 screw through holes in the CFC squares, then tapped 6-32 holes in a flat of Delrin.   The screws lock the CFC to the Delrin quite solidly.  The mill vise clamps down rigidly on the Delrin, which lifts the workpiece just high enough above the vise to avoid collision. 

I only need one of these Delrin jigs.  I will each side separately.