I have a 1" 3.0 CLR die. If i bend 180 degrees I end up with a 2" opening. See attached PDF for more info.
If you have a 3"
Center
Line
Radius Die and you bend a 180* hoop in 1" tube, then you will have an approximate inside measurement of 5" between the tubes.
3" CLR is a 6" diameter, so a 180* bend in the tube would be 6" on center, minus 1/2" on each side for the tube to get the inside measurement of 5", not 2".
BigJim is asking for a 1" tube on a 2" radius which would be a 4" diameter, on center, when bent to 180*. That would approximately leave a 3" opening.
You also have to take into account the calibrated radius for material stretch and any variances in the physical die size so you will probably end up with an opening around 3.25".