The ideal situation would be to go through both sides in one setup, both to save time and to retain concentricity, but sometimes the tooling required isn’t available, or the rather small and/or not very rigid routers most teams have are the limiting factor. I would guess the minimum to make this happen without too much chatter and flexing of the tool would be a 3/8" endmill. A larger diameter would be better, but most relevant routers can’t reasonably hold a tool of that diameter safely anyway.
This is an application where end-stops can be absolutely fantastic:
The intention of these is to create a repeatable X (or Y) axis stop to prevent the need for indicating during each setup. We used almost identical setups with ±0.0005 repeatability for reference standards and aeronautical components at a few of my previous jobs. They save countless hours of setup time over the years because once you do the setup once you know when you run the next part against the stops it will be in (almost) the exact same place.
Here is the process I have used in the past with various parts, both for work and robotics, that works very well:
- Mill flat the ends of the tubing you intend to use to size
- Place the stock in the fixture (vice/tubemagic/whatever) up against the end stop
- Indicate your part on the edges that are against the end-stops (typically back left corner)
- Run your first setup operations on the first side. We usually run this as one program, separate from the other, but you can simply put an op-stop in the program and tell the operator to flip the part
- Flip the part and run your second setup operations on the second side.
IMPORTANT: The axis you flip the part about is CRITICAL and completely dependent on how it was CAMmed. If you are rotating the part about the X axis, in CAM you need to set the origin of each setup in the correct location. I made a quick example below.
Fusion 360 Example Setups:
The original part:
I’ve added the 1 and 2 to better represent where the part is in space. Our first setup will be when the 1 is upright, indicated off the back left corner.
First setup (Part up against back and end stop):
Second Setup (Part rotated 180 deg about X axis and up against stops):
Notice how this is opposite from the model origin on the bottom of the part. We essentially changed the reference frame for the machine for this specific setup.
The below screen grab and beautiful artwork shows how the part will be rotated and how the setup coordinate axis change.