Rigid tapping with simple encoder

Hello. One simple question - is it possible to tap on cnc mill having simple encoder. I did added it to phase A - it outputs correct rps of spindle if seen using hal meter. But index goes only positive if look into its parameter.

I did this also to make closed loop of rpm of spindle - i do have variator between motor and spindle.

Now i got 6.48 impulse per rotation - 18 magnets on lower gear intermediate pulley with 50 tooth, while pulley on spindle have 18 tooh too. I could make it quadrature, but i still have only one spare input pin on parport.

Thank you !

Typically you need both quadrature and an index input for rigid
tapping  because the Z axis motion needs to be synchronized
with spindle rotation even as the spindle reverses direction.

 

How does emc2 takes not rigid tapping ? Or it still needs all three signals ? I have some weird float tap holder.

Which extends telescopically. But does not have any spring to hold in middle position. Will make some photos.

I will ask a different.

Now, i do have encoder. 6.48 pulse per turn. Example. 10mm depth thread, 1mm pitch thread.

I go to reqested xyz coordinates, turn on spindle cw, and feed z at 100/648 each pulse till 65 pulses count. Then ccw till 66 pulses count. And feed z same as before.

Which shell work with float tapping.

Some more head scratching. I think i will go this way:

pico-systems.com/bridge_spindle.html

+ just add one sensor with missing tooth (hole drilled in tooth center/ centers)

Or one still need both Phases A + B and index for riggid tapping ?