need to flip a piece of work
If you’re looking for advice on 2 side machining I would advise the following.
design in locator holes. These go all the way through your stock and match up with holes in your waste board. You can then line things up with a dowel or golf tee. When you flip the work the holes again line up as you machine the other side of the project.
be careful how you flip the work piece. Some designs are designed to flip top to bottom, others left to right. Be sure you flip the right way.
with two sided machining, the stock thickness is critical. It must match what the design software is set to use.
When I do two sided machining, I use Vectric V-Carve desktop. I start with an .STL file (the type used by 3D printers) and then I make Vectric create the tool paths. I often 3D print the design first to make sure that the .STL file makes what I want.
I’d make my part with a centerline down the middle and set up some fences on either sides and the ends to contain it. I’d make my X0 and Y0 on one end of the centerline.