According to coffee geeks its imperative to spend as much money on a decent grinder than on the actual machine (not to mention on coffee). Looking at prices from professional grinders this seems easy enough and after upping the game with the Bacchi, it was time to upgrade the grinder too. My Porlex hand mill has served me well and so I decided to actually build something myself that combines more sophisticated burrs with a simple crank in a compact package for the home. This seems to be a niche in the market too, since you cannot actually buy such a grinder (maybe except the hand made grinders by Orphan Esspresso, the Pharos and Lido).
I found a long thread in a german coffee forum, which described how user yoursong had developed a hand grinder around conical burrs from Mazza, the Robur burrs. So, I took inspiration from this thread, made my own mistakes and built a Hand Robur Mill.
My design uses Mazza Robur burrs with 71mm diameter as the centre piece, 3 aluminium plates and some wood in between. The structure is a little different to the one above, using 3 metal plates, because I looked to simplify the woodworks and increase stability.
The main difficulty was getting the axle right. Using two bearings, one above and one below the burrs, the goal was to ensure the maxiumum precision and stability. Initially, I planned to use a standard, threaded pole as axle, bur ran into three major problems: firstly, all standard threaded poles (8mm) are actually smaller and wiggled in the bearings, no precision. Secondly, fixating and centring the burr on a threaded pole is not easy. I tried with a number of nuts and washers, but it was never really centred. And lastly, the momentum with the 71mm burrs grinding coffee is quite big for the standard metal used in these poles. So, it simply bent within 2 turns of the handle.
After getting a hardned axle with a milled fine thread on one end and a shaft-hub clamping set, the mill started working! I have dialed in a few coffees now and I slowly getting to know the grinder. It works great and produces amazingly nuanced shots. Worth the effort? Well, I guess there are more dangerous absurdities than going nuts over grinding beans, but its about the perfect espresso, right?
Some more details:
I guess I spent around €250 on everything, but I am sure you can save quite a bit by not ordering everything to Belgium...