End of Travel limit switches.

I was working this week on upgrading a Lucas
horizontal boring mill to OpenCNC. This uses NC limit
switches for End of Travel of the X,Y, Z, and W axes.
These are all directional and drop out the E-Stop
relay which removes all power from the machine.
Cutting a wire in the circuit would also E-Stop the
machine. This is a fail safe mode.

I was always under the

> impression that NC was the switch of choice for
> limit switch's?