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RyanJE wrote:Jim, just curious, what RPM was the flat used at?

After all that quoting; that's the question? Not sure; Dominick did say he experiment with it and didn't get much difference.

Re ease of adjusting conicals: as has no doubt been pointed out before, the conical geometry causes the burr gap to change less per increment of burr adjustment, so if the same threads were used, conicals would indeed need more adjustment rotation per unit of grind change than a flat.

another_jim wrote:After all that quoting; that's the question? Not sure; Dominick did say he experiment with it and didn't get much difference.

All that quoting? I don't quite understand, but I was wondering because it certainly affects grind speed and flow rate.

RapidCoffee wrote:Both flat and conical burrs produce bimodal espresso grinds. The finer the grind setting, the more fines are generated. It is possible that conical burrs produce more fines than flat burrs, but experimental evidence seems pretty weak on this score.

Can you explain what you mean by "cluster closer together"?

My statement was not based on empirical data by me but compiled through observation and feedback by me and from other users experience. Observation: Conical grinds through their shape appear to adhere closer together within a greater range of time and less affected by changes to the bean such as aging and moisture.

cpreston wrote:Re ease of adjusting conicals: as has no doubt been pointed out before, the conical geometry causes the burr gap to change less per increment of burr adjustment, so if the same threads were used, conicals would indeed need more adjustment rotation per unit of grind change than a flat.

When I bought my Kafatek Flat, I recall Denis saying somewhere that adjustments of the Flat are half-as great as the Conical for the same result.

Makes sense, that is exactly how my flat compares to the conical I had (and the K10 notches as well).

The size of adjustment steps is a red herring; since the question is about how often adjustments are needed. The overwhelming consensus is that once you have a dose and grind setting on a conical, you can use that **unchanged** for longer and with more coffees than a fixed dose and grind setting on a flat burr.

There is no mystery on why this is -- coffees vary in brittleness and frangibility by bean type, roast, and age; and the output of conicals varies less with these input variations than does the output of flats. There is a big mystery on how this is -- what exactly is it about flats that makes them more sensitive to bean variations?

Well, the requirement of twice the mechanical/structural stability for the same grind stability might be a factor. Not sure of course.

another_jim wrote:There is no mystery on why this is -- coffees vary in brittleness and frangibility by bean type, roast, and age; and the output of conicals varies less with these input variations than does the output of flats. There is a big mystery on how this is -- what exactly is it about flats that makes them more sensitive to bean variations?

Jim, you may already have hinted at one reason:

The grinder artisans producing large flat burr hobbyist grinders need to experiment with well designed augurs. Conicals do not need them, flats do.

Beans may feed more smoothly into the vertical geometry of conicals, but "popcorn" more with the horizontal geometry of flats. This could even be a factor with a bean load.

redbone wrote:My statement was not based on empirical data by me but compiled through observation and feedback by me and from other users experience. Observation: Conical grinds through their shape appear to adhere closer together within a greater range of time and less affected by changes to the bean such as aging and moisture.

Robert, I'm not trying to harp upon this. But I'm still having difficulty understanding these claims. What is meant by "adhere closer together"? What studies/observations show a difference in shape between conical and flat burr grinds?