It looks like my 0.4mm nozzle has been damaged from repeatedly printing on warped sections. The hole is now 0.34mm and a strange shape. The nozzle is also no longer perfectly flat.
I was going to attach some sandpaper to the bed and move the head around over it to remove the warped section.
Thoughts?
In thinking it would be better to buy a drill bit on eBay for the correct size. Rubbing the tip over sandpaper will most likely drag burrs into the hole. Are you sure it’s not just burnt debris? On a makerbot at work, the nozzle gets clogged and the filament comes out all curly. I pull the nozzle off and hit it with a torch to burn the filament. Then I push a very fine piece of wire into the outside hole and gently floss out the debris. I use a microscope to do this which is very helpful. How did you measure the hole? If it is in fact oblong, the drill is the best bet. Good luck
@Eric_Moy I did the sandpaper method anyway using the finest paper I could find. There appears to be no burring, the hole is now the right size and the nozzle is level.
I re-drilled the holes in my drill press, snapping 2 bits in the process… 
I have ordered a new nozzle regardless. I only need to get through the next couple of days with this one.
@Eric_Moy to answer the burned in debris question… nope. The end of the brass nozzle was completely pummled, warping the hole.
Thanks for the input dude!
Glad to hear the sand paper worked. As for drilling, i was thinking using a pin vise and drilling by hand, but I’ve honestly never tried, only read. I have an eventorbot at home that I’m currently/continuously upgrading. I have my fingers crossed that my nozzle stays clear because it is custom, and terribly difficult to remove. If it ever does break, I’ll probably replace it with a more standard hotend. Glad it worked out
I’ve been using a little scrap of polarfleece and a binder clip to dust the filament. Have not had a nozzle jam in over a year. It seems to collect even the tiniest of particles, it’s very durable and lint free.
@scott_maher , awesome idea, I’m gonna have to steal that
yeah me too! so stolen