Hi All,

I'm thinking about building a hand grinder to go with my Pavoni Mod (brew and boiler pressure gauges, PID temp control, plumbed-in). The idea is based on poking inside two Zassenhaus grinders and a few flour mills. Espressoparts.com has a bunch of replacement burrs available. My questions are:

1. what are the best burrs to get?
2. is there anything clever in the mechanical design? Or, do I just need a shaft, two sleeve or ball bearings, and maybe a thrust bearing for the adjustment plate.

I'm looking at the Mazzer Robur burrs because conical burrs are very forgiving mechanically and the pre-chop part on the burrs makes an augur unnecessary. Plus all the hype around the Robur. Anyone know if this is reasonable, or should I look at the plate burrs more closely? Anyone have a drawing of the guts of a Mazzer mill? Is there anything clever about the adjustment, or just a fine screw thread?

This is going to be a hand mill for pre-grind dose-on-demand (ie, <25g capacity) but other than that I'm open to any suggestions.

thanks in advance,
raj

matadero210 wrote:Anyone have a drawing of the guts of a Mazzer mill? Is there anything clever about the adjustment, or just a fine screw thread?

PM sent. Let me know when you make the second one. I got dibs!

Cool project idea. You know, one thing I've always disliked about Zass' and the like grinders is not being able to replace the burrs. And since you're doing the designing could make it so the burrs are easily replaced. Especially since using Robur burrs for low volume low speed hand grinding they will need to be replaced...someday...by your posterity in oh maybe the year 2525.
Hey, even if man isn't still alive that grinder probably will be!

Coffee Geek wrote:It [Mazzer Robur] is forgiving, has super low RPMs (420 under load), yet it is powerful, and it can do roughly 17 grams in around 5 or 6 seconds, and the grind is superb. The conical burr set is a huge 71mm.

420 rpm / 60 seconds = 7 revs per sec * 6 seconds = 42 revolutions.... sounds doable.

Now will you need a gearbox to do it for the mechanical advantage? Probably. Now how many handcranks?

Jeff,

that's a good calculation there. If the grinder is mounted to a bench, then a 1ft lever arm will probably give plenty of torque (total guess). For my flour mill, the flywheel is set up for a chain, so you can power with a stationary bike. I'm not sure I'll need to go that far for coffee: its a lot more friable than hard wheat.

I've also been wondering about roller mills, which are preferred at the industrial level (see mpechicago.com; they have a really good page of articles and whatnot: http://www.mpechicago.com/coffee/TechIn ... Center.htm). Have a look at the articles. I'm not above buying a few test sieves (I already have the 40 and 60 mesh) and making some crude particle-size-distribution charts. If MPE is right, and roller mills grind TOO precisely (see their comments on "plurimodal" grinding, their term for mixing streams from two different roller grinders to make a blend), this could be kinda fun.

To make a roller mill, I've contacted crankandstein.com. They are curious about how many of us there are willing to make our own hoppers, &c, to make it worth doing a batch of rollers. If they decide not, it can't be that hard to make crappy ones on a lathe. Somehow, I think the Robur handmill will do better....

I think a micrometer head or other well-marked tool for adjusting the gap would be cool, although I'm not sure how to do it yet. The Zass design just uses normal, plastic bearings and a tensioning nut on the main shaft. Anyone know how to make this more precise than the GROF FEIN marked on the Zass bench/grain grinder?

best,
raj

Looking at the parts diagrams for the Mazzer Mini and Super Jolly, it seems that the beans fall into the burr set with no augur or paddles to get them going. Am I seeing this correctly? The Mazzer Mini burrs might even fit in my existing Zass housing!

raj

If you're going to make your own, you might want to get the three-phase Robur burrs. They're 83mm in diameter. A bit more difficult to find, but; hey - if you're building your own you might as well use the best! I don't know how exactly you're going to go about this, but you might want to just buy the whole burr carrier mechanism ... if it's available as spare parts.

Cheers,

Luca

Luca,

I agree, but I haven't found anyplace where I can buy the 3-phase burrs. I've sent email to espressoparts.com in hopes that they can order it (they have the 110 on their website). I'm also worried that they'll cost more than the $170 of the 110v burrs. Would be a shame to pay more than Mini prices for just a set of burrs.... Anyone know where to get the 220v burrs?

raj

ps: Anyone think the LM Swift would be a better set of burrs to work from? I'm tempted because ceramic knives have been quite successful, but not sure.

All,

I ordered the burrs today. In looking over the design alternatives, its not clear to me how anal the design needs to be. In Zassenhaus mills, the shaft typically has only one bearing, so that the inner conical element has a degree of wobble. This seems unlikely to be a good idea, although Zass has a good reputation for espresso grinding. Assuming I use two bearings, the only question left is how to do the adjustments.

I'd like to use a micrometer screw in the bottom of the mill to do the adjusting. In this case, the outer burr would be fixed, while the inner burr would move up and down, along the shaft, held by the screw on one side and a spring on the other. With 10# of pre-load, maybe the wobble caused by hand grinding will not affect the burr, but that's my main concern. (basically, I don't want the grind to change as I change my handle grip).

Lastly, I'm not sure how to insure that both burrs are centered perfectly (other than being careful while milling and drilling).

Will try to post some design ideas soon,

raj