Two issues, collet an air leak.
This is not the first time I’ve had these issues. so its something to be concerned about. So I do deep cutting jobs that ususally take 30min to 1.5 hours to complete. I’m taking off .25 of hardwood at each pass with the 3/8 or 1/2 in endmill or bullnose. (per manufacure recommendations.). What I see happening is the nut is coming lose and the bit slips down. If I catch it in time I can save the bit and the work piece. if I dont it breaks the bit and ruins the work piece.
I’m ordering a new collet, an maybe seeing if I can find a torc rench. But I swear I’m tightening down the nut hard. the only other thing I can think of is that after some use the nut heats up and that’s why it’s coming lose.
The other is an air leak after some time of use goes to change a tool and then their seems to be loss of air preasure. the only thing that fixes it is to reset the machine, which is bad if it happens the middle of your run. Charlie and I tried to find the leak but we suspect its a silinoid that gets stuck open. currently the cover is off the table under the tool rest. Carlie said it’s ok to run the machine while off. If you use the cnc and this happens try and find out where you hear the leak coming from and let someone know.