When cutting BSF threads there is a formula that allows one to derive the thread root diameter. This is very useful as it means you can turn a bit at the end of the tread to know when you are down to full depth.
It is Root Diameter = OD - (1.28066/TPI)
Where OD = Outside Diameter
and TPI = Threads Per Inch.
My question is , is there a similar formula to carry out the same operation on ISO Metric threads ?
My specific need being to know the root diameter of an 2 MM pitch thread on a 22 MM bar.
Dave.