title_body: How to clean an Iberital MC2/Challenge grinder that is stuck?
upvoted_answer: A couple useful posts found in a thread linked below.  Text below is two user posts.  LeeWardles post seems to have been accepted by the original poster as being correct information, but you can check out the whole thread below.
  
  CoffeeForumsUK
  
  awlred posted:
  
  
    I have an MC2 and recently pulled it out after my newer grinder
    breaking down. You can pop the top bit off the grinder (The black
    plastic part) and unscrew the worm-drive mounting. Doing this makes it
    very easy to get access to the top burr plate and unscrew it until it
    comes away. After that use a stiff bristled toothbrush or small
    paintbrush to remove all the ground coffee etc and clean the housing
    out entirely. 
    
    Assembly is the opposite of dismantling. As a rule of thumb I tighten
    until the burrs meet (the lower burr moves with the upper) and then
    loosen off about 1/8th of a full turn.
    
    Point to note The wormdrive, while being annoyingly slow to adjust
    needs to be in place for the grinder to remain dialed at any setting.
    
    While on the subject, an easy hack to make adjustments quicker is a
    set of locking pliers (welders pliers) either around the knob or
    straight on the bar. Which makes the whole process a LOT quicker, if
    slightly less elegant.
  
  
  LeeWardle posted:
  
  
    just needs a strip down. From what you have said it sounds like the
    grind is set to course (after you wound it back) so the noise is bean
    fragments. Also could be that one if the screws has come loose so the
    blde is loose on its mount. 
    
    Hold the button down that holds the step ring and unscrew the ring.
    This will leave you with the plastic ring and an cast alu mount for
    the top blade. Use a wire brush and clean this blade. Remove it and
    clean the mount, put it back. Next remove the lower blade. To do this
    safely unplug from the mains. To stop the motor turning while you
    unscrew place a large flat blade driver next to one of the fins. Clean
    it all and put it all back together. 
    
    Next set the grind to the right courseness. Dose a little onto your
    hand and rub the grouds with your figer. The grouds should be uniform.
    If not you need new blades. These shouldnt cost you anymore than
    £15-20. Makesure you get the right blades as some are right handed &amp;
    some are left. Don't forget, this grinder is made by Cunill and
    re-badged iberital so you can get blades from anyone. If your having
    trouble sourcing new blades leave your number and i'll get a supplier
    to ring you ASAP.