Ok, got things figured out…I want to share it here so others that find this thread have an ‘end to end’ solution…
- If you select a tool change for things like a 'flat bit' when doing letters/wide carves...it doesn't necessarily mean that ESTLCAM will do a tool change. You can choose a bit, but have the paths screwed up (not wide enough or whatnot) and it'll happily ignore the bit change since it's not needed. To find out if you have a bit change, check the gcode.
- M0 (M zero) is the way to go with the default Marlin FW. It'll stop the bit cold...in Repetier...you won't know what happened though unless you have 'ack' selected for the log...then you'll see 'paused for user'
- Here's the kicker...I haven't found a way to continue from Repetier. Which is fine....The screen doesn't cost that much, and provides you with the 'click to continue' button on the jog dial. I didn't understand why the screen was required or preferred for tool changes, now I get it.
- Neat trick that I need to document further...you can use M300 to play a tone/tune. And you can put this in ESTLCAM for tool change and 'finished cut' and it'll insert the gcode for you. This should mean that we could play one tune for 'hey bit change needed' and another for 'done cutting'. I'm going to try to do a fun video game tune or something happy. Here's some gcode for guns and roses songs: https://www.thingiverse.com/thing:446853
Thanks all for helping me through this, I can’t wait to do some carves tomorrow and have my bit changing gcode all setup…I’m hoping I can get down to my 1/16" bits I got from this site for cleaning up cuts and really start honing things in