servo motor selection, Jon Elson

>A dirty worst case cutting force calculation would show that
> the torque to turn the tool was .5 Hp x 550 Ft-Lb/Sec = 275 ft-Lb/sec
> A 1/2" end mill has a circumference of .5 X Pi = 1.571" or .131 Ft, and
> is turning 4300 times a minute, or 71.7 times a second.

Jon could you explain where the 550 Ft-Lb/Sec comes from in the sum above?
I'm not criticising you, you just didn't mention it and I was curious.

Thanks,
One of the many tens of Johns on here (John He)