Rigid Tapping on my PM-25

[ronster]

I'm wanting to do rigid tapping on my Acorn equipped PM-25. I have an 2000 per encoder to install and I am presently using the KBSI-240 for my spindle control, which works fairly well for most of my milling.
My confusion surfaces when I consider the alternatives if there are any to do rigid tapping on this machine. I've been told to just settle for standard tapping without motor upgrade to AC and a VDF. Ideas?

Thanks for help insight.

[cncsnw]

You do not need "exact" RPM control to do rigid tapping. Anything within 10% or so it close enough.

What kind of motor is your spindle motor?

I thought the KBSI-240 was a signal isolator (used with another drive, often also from KB Electronics). Are you sure you don't have another device powering your spindle motor?

[ronster]

Thank for the response. Yes, the KBSI is a signal isolator. I have a stock DC 750w motor and the KBSI-240 takes power from the Acorn 10v output, which is tweaked from 0vdc to 5vdc. The Acorn relays are wired for the forward and reverse direction.

[cnckeith]

Thank for the response. Yes, the KBSI is a signal isolator. I have a stock DC 750w motor and the KBSI-240 takes power from the Acorn 10v output, which is tweaked from 0vdc to 5vdc. The Acorn relays are wired for the forward and reverse direction.

see viewtopic.php?p=8876#p8876

and https://www.centroidcnc.com/dealersuppo ... ds/304.pdf

during rigid tapping the Z axis follows/chases the spindle encoder so it works even if the commanded speed isn't the actual speed of the spindle, it just doesn't matter see the video in the post above for the basics

[cnckeith]

also Uwe has a bunch of nice Rigid Tap videos.
https://www.youtube.com/@TheSuntravel/search?query=tap