How important is running the grinder while adjusting? - Page 2

Grinders are one of the keys to exceptional espresso. Discuss them here.
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#11: Post by aecletec »

My grinder has jammed after adjusting finer by a single notch when it wasn't running... never jammed during use. I figured by the sound it made it had an auto cut out. It was easy to fix just by making a notch or two coarser and then running it.

Ben Z.

#12: Post by Ben Z. »

cafeIKE wrote:FWIW, I've adjusted 3 Macaps, conical and planar, finer by 1 click / 2 teeth for more than 6 years with nary a whimper. Ditto several Mazzers, conical and planar, and 1 Cimbali Max Hybrid conical / planar.

It's possible to crush a bean between thumb and forefinger. Coffee is just not that tough.
Would I grab a 1/3hp motor with 2" shaft and try to prevent it from starting? Not bleedin' likely.
A 1.2hp Robur w 3" shaft? Are you nuts?

Any grinder that could jam due to 0.02mm decrease in burr separation would be mighty susceptible to jamming in normal use. Any grinder that does probably has a defect either in motor, starting cap or wiring.
Agreed in general, but your measurements on shaft sizes are a little off.

mitch236 (original poster)
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#13: Post by mitch236 (original poster) »

I guess I should fess up what this thread's about. I've been on a quest to find out why my espresso always underextracts. The last place I would have looked was the grinder. It is a Robur after all and they are supposed to be rock solid performers. Well after eliminating every other suspect (except my technique of course), most every person I've consulted agrees the Robur is the culprit. I've only had it for 1.5 years so I can't see how I've worn out the burrs pulling 5-6 shots a day. That's what got me thinking that maybe I ruined the burrs with my habit of making minor adjustments without running the grinder. I have heard a rumor that places some blame on the burrs themselves and maybe I got one of the bad sets. After all, I have no frame of reference to know whether my Robur is as good as anyone else's. I upgraded from a Mini and even a bad Robur has to be better. And up until my visit to Chicago, I had no idea how good espresso could taste. My espresso was always better than what I tasted locally so I thought that's what it was supposed to taste like. I always wondered how people claimed to taste all these fruits though!

Team HB

#14: Post by samuellaw178 »

It's almost impossible to ruin the burrs by adjusting without the motor running. Why? Think of the hardness level of your burrs, and also the hardness of the beans. The steel on the burrs is many many times harder than of a bean. Even if you adjust the grinder by a whole lot finer, the grind adjustment and the motor would be the first thing to give out first. Doesn't apply to Robur here because it's so much more powerful and beefier. The burrs I imagine would be the last thing to be damaged this way. By adjusting finer, you're just crushing the beans with the burrs, which is almost what the burrs are designed to do. :P If anything, an escapee stone or two would do much more harm to the burrs than anything else. Did you taste any rockiness or 'earthiness' in your coffee? That might be it. :P

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#15: Post by HB »

mitch236 wrote:...most every person I've consulted agrees the Robur is the culprit.
You can easily solve this mystery by getting another Robur for other side of your two-group Strada. Think of all the interesting side-by-side comparisons you'd be able to do! At least that was how I rationalized it. :lol:
Dan Kehn

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#16: Post by cannonfodder »

You are not going to hurt the burrs of any grinder by adjusting the grind with it not running. You may jam the grinder, but you are not going to physically damage the burr set. Make your adjustment and grind your coffee. If it goes Hmmmmmm instead of WRRRRR when you turn it on, turn it back off and back your adjustment out. Then re adjust with it running. I have made a lot of grinder adjustments the past decade, never had a grinder jam from a small tuning adjustment.
Dave Stephens

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#17: Post by cafeIKE »

Ben Z. wrote:Agreed in general, but your measurements on shaft sizes are a little off.
Approximations of burr diameter

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#18: Post by civ »


FWIW, I have a Cimbali Max Junior and while practising some modifications on it measured the travel of the upper burr in relation to the turns of the worm gear to be ~1.0 mm in 44 'clicks'.

A 'click' is a 180° turn of the worm gear axis and 44 'clicks' represent a ~ 120° turn of the upper burr carrier.

Doing some math, it's 1.00/44, which comes to ~ 0.0227 mm per 'click'.

The routine I use with this grinder to adjust the burrs after cleaning up is ~+4 clicks from zero (burrs touching), which turns out to be about ~ + 0.091 mm travel and from that point on it's + 1 to 3 or 4 'clicks' as I try to get the right setting for the coffee beans I'm using.

All in all, I'm starting off at ~ + 0.091 mm and ending up with a max of twice that, ~ 0.182 mm., which means a +/- travel of ~ 0.091 mm., well below 1/10 mm.

Although these values may vary considerably from grinder to grinder, my guess is that unless there's something much harder than a roasted coffee bean between the burrs or some other motor related issue such as low starting torque, jamming would not be caused by moving the burrs without the grinder running.

And then, I could also be wrong.



Measurements posted are approximate and the math could well be off as it's it's rather early in the morning.

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#19: Post by benm5678 »

Cool, this thread convinced me to stop worrying about it too much. If need to go finer more than one notch, can just move it one, run motor a bit, and move again... but still so much easier and controlled than trying to run a Major continuously while adjusting.

Mitch - in your under-extraction tests, did u ever run the grinder with a full hopper, with significant amount of beans.... might be interesting to try.

mitch236 (original poster)
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#20: Post by mitch236 (original poster) »

benm5678 wrote:Mitch - in your under-extraction tests, did u ever run the grinder with a full hopper, with significant amount of beans.... might be interesting to try.
Yes, I tried every possible scenario I could think of except replacing the static screen which makes the grinder so impossible to run efficiently, if it were necessary, I would sell it. I may sell the grinder anyway. I expect to get a K10 delivered today and will run some test shots. I realize I may have to be patient until the burrs are seasoned. I also ordered new burrs for the Robur. I don't really have room to keep both (especially since the Strada is so big). Once I get both grinders up and running, I will decide which one I want to live with.