[Robert]

This article describes the ASBC method to adjust your mill in order to get the maximum extract.  For a 2 roller mill, all you need is a #14 seive, which costs $20 shipped.

When you crush, you want to be left with approximately 50% of the grain in the sieve and the other ~50% in the pan (where the total - 100%.) It's not difficult or expensive to set your mill correctly with this method.

If you trust someone who's apparently done it for you.... In their Water book, Palmer and Kaminski report that, taking the ASBC definition of coarse grind, 75% remaining on a No. 30 sieve, the closest approximation to this result on a two roller mill was found by Kai Troester to be had with a gap setting of 0.8 mm, ~0.32 in.  FWIW, at least as a point of reference.

[hopsindahood]

All mills are not alike, though.  This is why the gap number isn't always ideal.  My mill has knurled rollers and the gap I use is not the same as what I use on a smooth roller mill at my local homebrew shop.

[Robert]

All mills are not alike, though.  This is why the gap number isn't always ideal.  My mill has knurled rollers and the gap I use is not the same as what I use on a smooth roller mill at my local homebrew shop.

True.  Some day I may get a sieve set and see what I'm getting just for giggles.  But more important to me is the practical result, by which I've dialed mine in by trial and error.  Coincidentally, to 0.032 in.  Which as you rightly point out would not necessarily translate to everyone else.  I suspect that not only surface treatment of the rollers, but also roller diameter makes a difference.  My 2 in. rollers no doubt pass the grain through differently than the more typical 1.5 in. homebrew rollers, or 6 in. rollers on a pub brewery's mill.

[BrewBama]

Though it would be fun to run an assay, even with the information I wouldn’t change my gap gained thru [painful] trial and [lots of] error on my system using my mill, processes, volumes, pump flow setting, etc.  I would not adjust the mill gap because a textbook tells me this is the ‘proper’ mill setting and I’m doing it wrong.  Great starting points that weren’t optimized with me and my cobbled together system in mind.

Having said that, it makes me wonder how many homebrewers experience a stuck lauter because of excessive flow rate yet blame it on the mill setting.  Grain bed compaction is probably to blame for a stuck lauter more often than not as a result of high flow pumps not throttled back enough.  These pumps we use (Chugger, March, Riptide, etc) are way over rated for the task IMO. ...and a ball valve fitted as a throttle is pretty difficult to set repeatably for a desired flow.  I’ve resorted to a digital caliper to set my pump’s output linear flow valve (I have been using 5/32” but I’m planning on using 9/64” Fri).


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[Robert]

+ 1,000,000

BrewBama,  you first alerted me to a post on Dave Miller's website that helped me confirm, mathematically, that my velocity (NB: it's velocity, not flow rate, that matters) as empirically established was correct.  That rate, for me, and it's going to be in the ballpark for most homebrew systems, is around  0.25 in/min.  Which for me is about 0.67 qt/min.  (Depends on geometry and loading,  but it's all in a range.)  Almost all homebrewers running systems with a recirculating pump are so far exceeding this as to be absolutely terrifying.  There's no adjustment in crush that will save your @$$ if you're running your pump like that.   (No, I don't have a pump.  Gravity still works in my bit of spacetime.  And I still have to rely on my use of a simple bottling bucket spigot, not a 1/2" ball valve,  throttled almost to closed position, as the outlet on my lauter tun, to sufficiently restrict flow.)  Slow your roll, people.

[BrewBama]

I wish I had a manometer.


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[denny]

I have no idea what my mill is set to and I don't care.  I care about the grist, not the gap.  It will differ for everyone depending on their system.  20 years ago I set my mill as tight as it would go and I've never changed it.

[BrewBama]

I imagine size of barley corn may influence mill setting as well.




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[pproctor]

Here’s a great podcast that is counterintuitive and recommends going to higher gap settings. I’ve taken mine to .045” and seen my efficiency rise but also a bit less consistent.

http://masterbrewerspodcast.com/079-brewhouse-efficiency-for-the-small-brewer


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