It is documented that for spindle control one can connect a spindle quadrature signal + index.
My question is: Is it sufficient to only use a single channel + index?  That is use channel A & I  rather than A, B & I
The primary purpose of a quadrature signal is to get both position and direction, however I am not interested in direction so the B channel is unnecessary theoretically but whether that applies in practice depends on the Mach3/Galil/plugin requirements and that is what I don't know.  I have a single spindle pulse string already and I do not want to change that for full quadrature unless I really have to.

A related question.  I have read that Mach3 only uses a single spindle index pulse to set the feed for threading.  If you use multiple pulses/rev, and tell mach3 how many, will it adjust the threading feed multiple times per spindle rev?  If not, is there any reason not to trick it like;
Say we have 4 pulses/rev and specify a 0.25 mm pitch thread, will we get a 1 mm pitch thread?
For the record I want to make some accurate pitch threads and adjusting feed once per rev seems very coarse.

Thanks in advance for knowledgeable replies.