One of the downsides of a CNC mill: when the toolbit gets hung up it is easy to snap it off. That is exactly what happened to me today while cutting a 3/16″ slot 3/8″ deep in aluminum.

The debris doesn’t clear very well from such a slot so I was periodically brushing the chips away. What I didn’t realize is that the chips need to be cleaned more frequently as the slot gets deeper. This would have been obvious if I’d been doing it by hand, but of course when I’m sitting back watching the machine work I had no idea of the stress that was building up. It was on the last pass when I heard the steppers start to whine as they were working much, much harder. I quickly hit the emergency stop button but it was too late. The picture here shows the result.

Fortunately the Sherline end mills are double-ended so I’ve got another one to work with. I’ll have to order a replacement though, and next time I’ll be much more cautious about this.

On a similar topic, I have been using SheetCam for generating g-code and EMC2 for running the mill today and I really quite like the combination. I’ve been frustated with the DXF generation from Inkscape but that is a different story altogether. As soon as I get everything set up again I’ll capture some video of the process and pictures of the results.