Mach issue with my mill

[Rich05]

A new problem has appeared. When the spindle is running the keyboard and mouse become scrambled. They give random inputs when I press on the keys. This does not happen if the spindle is not turning. It clears up as soon as spindle stops turning. Any ideas? thanks R.

[Al_The_Man]

Most likely a Grounding issue, if your PC is desktop or tower, the PC power supply common is at the same potential as your spindle (neutral), if it is an AC motor or DC SCR controlled from the 120v mains supply.
I would guess that the majority of 'noise' problems is the lack of proper grounding of the parallel port and the service ground to a common point in order to create zero potential difference between the two.
Al.

[Rich05]

thanks Al. As allways you are a great help. Any suggestions on how to beat the grounding issue?

[Al_The_Man]

First off I would not rely on the MB ground screws, I would take the common where it leaves the Parallel port and take it to a common ground point where the service ground is also connected.
The spindle motor frame ground would also go back to this point.
Al.