Hi,

Are conical burrs inherently better for low retention?

Both the DF64 and Eureka Oro SD flat burrs grinders use bellows. The conical burrs Niche does not. Same for the end-game (unreasonably priced) grinders like Weber Key and MC4. Any counter examples?

I would prefer not to have bellows. Feels like a kludge. On the other hand, consensus seems to be that flat burrs is better for milk-based espresso drinks (flat white is my drink of choice).

Daniel

The MC4 does come with Mr Puff and it helps in getting more grounds out. I think there is a benefit to conical where the grounds can fall straight out of the burrs, vs flats when they go out the side of the burrs and need to be swept away.

Daniel_R wrote:Hi, Are conical burrs inherently better for low retention? Both the DF64 and Eureka Oro SD flat burrs grinders use bellows. The conical burrs Niche does not. Same for the end-game (unreasonably priced) grinders like Weber Key and MC4. Any counter examples? I would prefer not to have bellows. Feels like a kludge. On the other hand, consensus seems to be that flat burrs is better for milk-based espresso drinks (flat white is my drink of choice). Daniel

It's way more complicated than flat vs conical. The Sette grinders, which are conical, have a straight-through path to the portafilter. However, they also have a slotted grinds distributor. That distributor, especially for oily coffee, will retain some grinds. Admittedly, not much, and most folks consider the Sette grinders zero or low retention. On the other hand, some flat burrs grinders (maybe all?) have little sweeper arms to help the grinds to exit. My Feilei ZF64W grinder, for example, has these sweepers. I ordered it with the optional bellows for single dosing and to purge the grinder. To my astonishment, when I used it to purge the grinder, virtually nothing came out.

It seems that you need bellows with a lot of grinders including Levercraft Ultra even with its RPM profiling. Lagom seem to have gotten it good with the P100 however, with its auto RPM purge and knocker-chute, reports from owners say no WDT and still little retention (it's advertised as +/- 0.1 with and without RDT).

How's the retention on vertically mounted flats like the Bentwood or the Xeoleo? At least on paper they might mitigate retention with gravity.

Hi,

Just noticed that the Lagom P64 is a low retention flat burrs grinder without bellows or knocker.

Daniel

mikelipino wrote:How's the retention on vertically mounted flats like the Bentwood or the Xeoleo? At least on paper they might mitigate retention with gravity.

I thought flat burrs feed the grounds by centrifugal force. How would that work with vertical flats? Also, most low retention flats has them tilted. Why?

Edit: found this thread

How do vertically mounted flat burr grinders work?

but it doesn't really explain.

Daniel

Daniel_R wrote: The conical burrs Niche does not.

I found the Niche benefits from a small bellows as well although it doesnt come with one. Depends on humidify in your environment and if you rdt and if you rdt to much.

Bellows? That's seems like just getting out some dust.

Sweepers? Maybe a bit gets caked in there, but putting the grinder on a tilt or horizontally solves that.

Silicone Flaps/clump crushers? To me THAT is the thing I'd avoid on a true single dosing, low-to-zero retention flat. Some is going to get stuck behind those every shot and come out on the next shot. I took mine out on my F8 (sure, not a true single doser) but then you have to deal with static and probably won't get the grinds to fall so nicely in the basket (but, ironically, you will get more clumping, in my experience).

Do billows push enough air to clear that flap though? Then it would be very useful! Do they? Or is it really just clearing dust like I would think? If not, I wouldn't worry about bellows.