But if it can be used with thick walls. It is not necessary to use the space, but less less.If the task can use the thick tube is 0.014 ", it is possible to manufacture the coil fins as FPI away stage 12.
You can use pipes with wall thickness up. It does not require the space of a little less if they will be able to use a pipe thickness 0.014 ", it is possible to produce a coil spacing is 12 FPI.