Lathe has an existing encoder with 4ppr, is there a way to configure as index?

The spindle has a tach on it with 4 pulses. I have rewired it so the tach is powered by the breakout board and I am reading the signal. Is there someway to use this as index for threading, maybe some way to scale 4 pulses down to one for indexing?

Also, I have a 600 ppr encoder and I am maxing out at about 350RPM like everyone else using parport. Is a 100PPR encoder a better solution for spindle encoding with parport for threading?

thanks.

Not entirely sure how to do it, but the encoder component has a counter mode that might help.  Count three pulses and on the 4th, reset the count and trigger the spindle index?

It may be easier to just hook up a proximity sensor or optical sensor (they're cheap) to your BOB and trigger a once-per-turn signal using a disk on the spindle (or even a plastic collar with a metallic set-screw).

As for encoder PPR, I think folks have gotten away with pretty low resolution encoders for threading.  Do the math based on your highest spindle speed and max parallel port input freq... maybe you can get away with a 200ppr encoder.

Thanks for the response. I was thinking of using a second encoder (or something) and piping some modulo into the index of the first but It should be pretty obvious I don't know what the heck I am doing and I am not sure of the timing of events anyway.

I lowered the base thread period to 45000 and I am getting up to about 550rpm now in counter mode. I ordered a 200ppr ABZ encoder from China, so that should be good for 1650 RPM. Should be good enough for anything I need an encoder for, for now. The lathe has max 2500RPM. 
 

Dont know if they will fit your lathe, but in looking for encoders for my servos I recently found th CUI AMT102-V encoders that have selectable PPR. They are cheap, like $25 or less per. I just ordered 4 as the 250PPR on my mill work out to 1000per rev in quadrature mode causing a big performance issue that I lived with a long time. They also have an index pulse they claim.

cncjerry wrote:

Dont know if they will fit your lathe, but in looking for encoders for my servos I recently found th CUI AMT102-V encoders that have selectable PPR. They are cheap, like $25 or less per. I just ordered 4 as the 250PPR on my mill work out to 1000per rev in quadrature mode causing a big performance issue that I lived with a long time. They also have an index pulse they claim.
 

Im using an AMT commutation encoder on my lathe servo spindle.  Yes it has an index.  And the ability to auto-phase the hall signal makes it really easy to use as a retrofit on servos or simple BLDC's with encoders or resolvers that you can't read for some reason.