I found a way to get an accurate spindle tachometer reading from my LMS 3960 mill converted to CNC. I use Mach3 which accepts pulse input for spindle rpm. I used an infrared transducer mounted close to the spindle and reading the spindle lock hole. It remains accurate up to the maximum spindle rpm, 2500 and works with the LMS spindle control kit and Mach3 feedback loop. The transducer is about $25 plus shipping. If anyone is interested I will be happy to supply the details.
Bill
Bill