[Rainman229]

Whats the reason for the red button on the Syil SX3 if it don't shut the cnc down as well as the spindle. Mine just shuts down the spindle and nothing else as i come to find out. And not in the pleasant way of finding out either. Just curious as to why they went this?

[neilw20]

There is a free 3 pin connector on the breakout board near the corner close to the ribbon cables.
If this connection is bridged, I believe (have not tested it) that the drivers will be disabled.

You would need to organize a safety relay driven from the E-Stop signal.
An opto coupler with driven via a 1K2 resistor from the e-stop line with the output to pins 1 and 2 of the 3 pin connector will probably work.

On a 6 pin opto. eg 4n35
Pin 1 opto via 1K2 resistor to E-Stop pin 2.
Pin 5 opto to Enable pin 2.
Pin 2 and 4 opto to pin 1 of enable connector. (0v)

Don't even go near the front panel E-stop wiring as you are ensured of creating smokey havoc.
Attached PDF shows the SX3 BOB circuit.

Problem with above, is that disabling the driver means when E-stop released, steppers will with 50% certainty be one step out, so you need to reference again.
But as you already panicked, you had already lost the plot any way.

Usually, in a timely manner, hitting the space bar on the PC pauses Mach3 and Alt-r will gracefully resume, (but test it first!!)

Some canned cycles like circles and drill cycles resume at next vector, so expect a crash on restart!.
The safest, most reliable way I have found, is to hit single step, and wait for it all to stop nicely. This does not stop the spindle. Hit F5 when movement stops.

I have only used the E-STOP once in 3 years. It is only for emergencies, and I have even seen big machines, that kill the spindle, and keep feeding. Really dumb stuff.

[ataxy]

yeah big machine tend to do big mess some time, i remember seeing a big machine at a place i used to work, it simply decided to take a vacation for no appearent reason just wam straight in the table the endmill it had was reduced to dust and actually most of the tip of the sindle was to since it sort of melted into the vise

[Al_The_Man]

With 'Big Machines' the likes of Mits/mazak/Fanuc etc controllers, it all depends on who programs the machine control side (ladder) as to how functions are going to react in an emergency.
Anyone worth their salt is at least going to implement a feed hold on a spindle fault detection or if feeding with a spindle Not-Up-To-Speed signal.
Most have servo fault detection on following error detection that will shut the servo's down or issue an E-stop.
The Fanuc and Mitsubishi controller itself will shut the machine down if the servo feedback signal is lost or not valid.
Al.