Manual Grinder Effort and Burr Geometry

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

This is going off topic, but I would think that larger diameter burrs=larger cutting surface=more beans ground at any given point=faster grind times with fewer turns. It's very odd to me that Pharos 68mm is faster than HG one 71mm.


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drgary
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#2: Post by drgary »

pacificmanitou wrote:This is going off topic, but I would think that larger diameter burrs=larger cutting surface=more beans ground at any given point=faster grind times with fewer turns. It's very odd to me that Pharos 68mm is faster than HG one 71mm.
Actually a photo thread last year showed the inner surfaces of the 68mm and 71mm burrs to be identical.
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fivethirty
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#3: Post by fivethirty »

pacificmanitou wrote:This is going off topic, but I would think that larger diameter burrs=larger cutting surface=more beans ground at any given point=faster grind times with fewer turns. It's very odd to me that Pharos 68mm is faster than HG one 71mm.
Still off topic but I have a first run 83mm HG and I reckon that I grind one gram for each turn of the handle, and that has been the same since the outset.

I can't be sure, but in later runs of this grinder I seem to remember that Craig and Paul elected to coat the burrs for longer life (?)...

Perhaps this has the effect of somehow requiring a more protracted running in period, that amount of turns at the outset must be a little disconcerting.

pacificmanitou (original poster)
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#4: Post by pacificmanitou (original poster) »

That's what I thought. My Pharos does about the same rate, which is a moderate improvement in a month of use, starting at 27. I would expect the large conicals of equal size to perform equally, with the 71mm matching 68mm. I'm guessing there is something else at play within the burrs that allows lower force turns rather than fewer hard turns. Perhaps the top channels of the burrs are different, feeding a different quantity of beans at a time.
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FotonDrv
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#5: Post by FotonDrv »

I think the grinding effort has very much to do with the age and surface coatings of the burrs. I have a Pharos, an HG-One with both the 71mm & 83mm burr sets, and I tried the 83mm "Aftermarket TiN Coated Burrs"

I did not keep the TiN coated burrs because it took so much longer to grind the same amount of beans. Granted, I did not break them in but I was not sure who or what was going to break in first, them or me! They had about the same cranking effort as the well used 71mm burrs.

The 71mm burrs of the HG-1 had about the same cranking effort as the Pharos, maybe slightly more. The differences were offset by the ergonomics of the 2 different grinders in favor of the HG-One.

As far speed of grinding goes for grams/turn? Not sure because I was more concerned with effort.

Here are the 2 burr sets of the HG-1, I do not have photos of the Pharos burrs.





Sorry for the crappy photo quality!
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pacificmanitou (original poster)
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#6: Post by pacificmanitou (original poster) »

FotonDrv wrote:Here are the 2 burr sets of the HG-1, I do not have photos of the Pharos burrs.
Pharos inner burrs look remarkably similar to the 71mm

I wonder what abou the TiN coating makes grinding so much more laborious. It seems like the head blasting ought to speed up the break in process rather than have the opposite effect.
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sanzrobinson
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#7: Post by sanzrobinson »

This is the same mystery as the Vario which has 54 mm flat burrs, but apparently tastes like a grinder with larger burrs.

This highlights how burr design is a black art, which depends on much more than just the size. Rather geometry, materials, cutting pattern etc. play a big role. However, this information is not available to the consumer... we can judge the results in the coffee we drink, but have very little knowledge of the extensive engineering that I'm sure goes into developing a burr. I imagine most of this information is trade secret, although some of it is patented and available (e.g. http://www.google.com/patents?hl=en&lr= ... rs&f=false).

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pacificmanitou (original poster)
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#8: Post by pacificmanitou (original poster) »

That patent looks to be for the kind of bulk burrs in grindmaster brew grinders. There is a design that I never understood...
Its certainly true that the black magic involved in burr manufacturing has a lot to do with performance, the details make the difference it seems.
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