The only reason we use 120% as the load limit is that the spindle can be run for 30 minutes continuous at this load before it times out. We do production work and time is money so we want to push things as far as is sensible. The load actually does go a bit above 120% because the feed drops in 10% increments and if that is not enough the keeps climbing a bit.
The reason I suggest using this feature even when you do not need to push things is that it protects your tools. If you stall the spindle it is nearly always bye bye tool. Also if you cram a holder into a vise or something the increased spindle load will back off the feed and reduce the chance of serious damage.
On a similar note I always start the spindle before doing the first rapid move into position. This way if you have goofed and rapid your spindle into the part or a vise jaw it hits spinning. Admittedly the spindle overload feature is not active in rapid so the feed does not slow down until the servo overloads or gives a following error. However, when the spindle hits turning there is much less chance of destroying your spindle bearings; if you cram a stationary spindle into something really solid you have a chance of 'brinelling' the ball races and that means bye bye bearings. Google 'brinelling ball races' to find out what I am talking about.
When you do this sequence to save time you have to turn on SPINDLE NO WAIT. This means that if the line immediately following the M03 command is a rapid move the machine does not wait for the spindle to come up to speed before it executes the rapid; it waits at the end of the rapid for the spindle to be at speed before a feed move.
I think SPINDLE NOWAIT is a parameter but I am not sure.
When you change Settings or Parameters the old value gets stored in the Alarm list but it is a good idea to record them for reference so you know where you are. I think the only way to set them back to the factory values is reload them from the memory stick you got. Which, incidentally I would back up onto another stick and reload from the back up just in case I fat fingered somethging and finished up saving the modified values onto the stick rather than reading the stick values into the machine...easy to do
