This should hopefully aid anyone who has purchased a old (or new, they haven’t changed much at all) Rancilio MD 50, or Rancilio MD 40, or perhaps even a Rancilio Rocky - as i would imagine that they are somewhat similar in design. I purchased my grinder, the Rancilio MD 50, from a popular auction site, then went to collect it. It was made in 1994, but had been left unused for at least 5 years. Most of the parts were present, but it was very dirty and the burrs had seized during their time of storage.
Steps to disassemble
First remove the top hopper, this is simple, remove the four visible screws within the hopper, there is a bit of plastic which sits within the hopper which has a magnet on the underside - i guess to catch any screws which might fall deeper into the machine, or to stop any magnetic metals which might find themselves in your beans. This is the first indicator of how well made this machine is.
Scoop out any remaining beans from the grinding mechanism - this should reveil the brass top burr housing complete with arrows directing you in the direction in which you should unscrew this top burr, before taking off the top burr you will need to remove the circlip from the grinder ajustment wheel and pop that off. The top burr housing was completely fused due to heavy usage then dormancy for a few years prior to the grinder coming into my ownership - i found a quick tap with a plastic hammer jolted it free.
Note: The top burr unscrews in a normal anti-clockwise way, not, as i”m led to believe clockwise which is normal in the Mazzer grinders.
Once you have this top burr off you will now be able to see the extent of the grinding mechanism - when i peered down into this i knew that a deeper clean would be needed. If you are just replacing the burrs you are nearly done. The next step is to remove the large nut which secures the lower burr, this is made slightly difficult as the botton burr is free to rotate, i found that by placing a screwdriver into the mechanism into the exit chute you could jam the grinder from turning, and therefore loosen the nut and washer. Once the nut is removed the lower burr and housing should come out.
Note: At this stage if you are just performing a burr replacement then this is all you need to do. Simply unscrew the bottom and top burrs from their housing and replace them. I found that it is worth clearing the screw heads of muck before trying to unscrew the burrs as not to risk rounding off the heads.
At this point we”ve got the burrs off - for most this will be enough to service the machine, and replace the burrs. You will be able to see three alan key type bolts now that you have the burr housings out. These secure the motor - leave these bolts for now, we will remove them later. For now flip the machine so that the bottom is exposed.
Unscrew the mesh which protects the machine innards. Two screws are visible, and two are joint use, securing the rear rubber feet.
At this point you will be able to see four threaded rods. These rods are how the whole machine fits together. The electrics are secured to a metal plate, this is threaded onto two of the rods and bolted down, remove these two bolts next.
I used a camera at this stage to take photographs of any wires which i disconnected. I managed to leave most of the wiring in tact however i did detach the mains input into the machine, this is three wires: the earth, ground and live. Disconnect these wires next and remember how the connect them back to the connector.
There are four switches used: In the doser at the top there is a paddle which when pushed stops the grinder, this is used to stop the machine when the doser is full. In the bottom of the doser there is a microswitch which starts the grinder every six doses. The manual rocker switch - this starts the grinder going, on mine is it orange on the left on the front of the grinder body. The main power switch, this is on the right side of the grinder.
To remove the casing, which is the next step, you need to disconnect the wires from the orange rocker switch, make sure that you take a photograph of how the wires connect into this before taking them out.
The next switch to disconnect is the one in the bottom of the doser, i found it best to disconnect the wires inside of the unit rather than at the other end in the doser. To do this i had to trace the wires back, then unscrew a crimp style connector, this released one wire, and simply unplug the second from a connector.
With all this disconnected it should be possible to, unscrew the mains power switch from the base of the unit and remove the base, and then slide the cover off, gently feeding in the wiring loom and doser switching wire through the holes in the casing. You should now be able to see the motor and attached wiring.
With the casing off you can unscrew the motor mounts on the top casing, these are alan type bolts.
Hopefully these steps will have given you enough information to disassemble enough of the grinder that the rest becomes obvious. What struck me was how well made the whole unit is, and how large and heavy the motor was. I reassembled mine and it”s grinding coffee with haste and consistency.
Conclusion I’ll give the grinder 10⁄10
It should be noted, it is big, it is heavy, and it is tall (so tall in fact it wont fit under a standard kitchen cabinets). However if you want and absolutely fantastic grinder which will last for years then you can do a lot worse than the Rancilio MD 50, and for the price i paid it was cheaper than a new Rancilio Rocky, albeit a little more work to get into a usable condition.