chlorox I just urge caution until things are proved based on considerable experience in the coffee area. I posted this about burrs on HB, hopefully you will find it interesting, especially @tompoland as I believe there was a post about expectations of 83mm Mazzer burrs performing the same in different grinders (also remember there are 2 variants of the 151B).
Sure I helped with the design, testing and specification of the Duo grinder and you may believe I have unconscious bias, however, I don’t make any money if you buy it, I don’t have a Patreon, I don’t monetize my channel even though I could and I have not put videos up to get clicks and views. I’m about as honest and knowledgeable as you are going to get and my past 20 year record speaks for itself. I don’t have to continually proclaim my honesty and depth of knowledge the moment I am butt hurt like some do. I don’t have hidden connections and I test properly. I don’t even call myself the “burr man”, I would be embarrassed to do that. I can only say, after many years, I know a little bit about burrs.
**maccompatible wrote:**I’ve heard the popular claim that slower RPM = less fines. A recent Lance Hedrick video claimed that RPM does NOT affect fines, but rather affects peak particle distribution. I haven’t really seen data either way, so this would be an interesting part of this discussion if anyone’s done it.
Do you have the link for that, I probably have not viewed it, but what is stated doesn’t match my own tests and results over more than 5 years. In fact, the EK43 results sound far more plausible with the types of burr sets being used and it doesn’t surprise me that the EK43 would produce more fines, it’s exactly what I would expect.
I suspect there may be reasons for the claims, specifically with the Sculptor only going as low as 800 rpm and severely torque limited at that RPM, as are many variable speed grinders at their minimum rpm. Other things apart from torque, such as burr geometry, carrier and sweep arm design etc.. all contribute to running at a low rpm being quite challenging, again something I have worked on for over 18 months.
by jfjj » Mon Apr 17, 2023 2:13 am
I saw that and kinda confused me a bit. I’d like to see the data on that. So faster RPM shifts to finer??
Faster RPM doesn’t produce finer particles because of speed per se. Rotational speed affects burr distance for any given grind, this burr distance dictates what I call “burr packing”. These things, plus geometry, affect feed rate, which together affect grind quality for any given burrset. It’s one of the reasons conical hand grinders work as well as they do and slow moving conical burr sets work better.
It’s a fairly complex area, but recent grinders I have played with which allow you to check the Micron distance between burrs support my views. I suspect as the grinder world moves forward, these effects will become far more important and “variable speed” will either be done right, especially as manufacturers aim for lower rotational burr speeds and overcome the challenges this poses. The challenges are, burr geometry, torque, feed rate and chamber clearance. There are certain rules that need to be followed and many burr types I have seen won’t properly support low speeds.