Where as I typicall use the following definitions:
|R||Inside bend radius||inches|
|K||%/100 of T for neutral axis||unitless||t/T||0.33 is standard|
|BA||Bend allowance||inches||material around the bend|
|BD||Bend deduction||inches||material removed from flat for a bend|
|BD=2 SB -BA||14||0.0747|
Now to the real problem. Every combination of machine and material result in a different N and R.
You have to find out how your machine works and the pressure settings used.
Most of the time N=1/3 or 0.33 is good enough. But as you go from 14 gage to 10 gage carbon steel, N moves from 0,33 to 0.4