Setting a Monster Mill Correctly

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wfred

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I have been getting consistently low efficiency since I began brewing all grain. I have a 10 gallon cooler setup and I fly sparge. I have tried every trick I have been recommended from lengthening my sparge time to batch sparging and haven't seen any significant changes.

Normally I buy my grain and build my own recipes but I wound up ordering a kit from Northern Brewer and had it crushed by mistake. When I brewed that batch, my efficiency went up closer to 78% from the 65% or so I have been getting. I fly sparged that batch for 60 minutes and did everything else essentially the same as what I would normally do except for the fact that this was a kit that was crushed at Northern Brewer.

Now I feel like I have isolated my problem, it appears that I am not getting the correct crush on my grain and therefore am not getting complete conversion and am getting low efficiency. I have a Monster Mill MM2 with the hopper. I use a 1/2" Milwaukee corded drill to power the grinder. I haven't adjusted this mill since I bought it earlier this year.

Am I on the right track and if so, how do I dial in my mill to get better efficiency without crushing my grain too far and causing new problems?

Thanks,

Fred
 
With only 2 rollers you'll want to mill it twice. Set the gap using feeler gauges to .040 inches and your efficiency should go up. I had a three roller monster and it was very unstable. Eventually sent it back for a cranken...
 
With only 2 rollers you'll want to mill it twice.

That is a completely false statement with a properly gapped 2 roller mill. Maybe because you're used to using an LHBS mill which are usually not very tight so milling twice helps. I've always used a 2 roller mill and when set with the right gap I've never had to mill twice. I average 80-85% batch sparging on all my beers.
 
I know I'm in the minority, but I set my gap as close as I can on the MM until it binds and then back it off just a bit. I crush as fine as I can get it. I've never used feeler gauges for setting it.
 
With only 2 rollers you'll want to mill it twice. Set the gap using feeler gauges to .040 inches and your efficiency should go up.

As Cmiyc stated, this is wrong. You don't need to mill it twice, simply tighten the gap. it's easy to do, you loosen the two set screws on the second (non-driven roller) side and adjust with the knurled knobs to move the roller closer. For now, if you don't have feeler gauges you can use an old credit card, I say old because the rollers will scratch the magnetic strip up. Tighten the knobs until they grip up against the card then tighten the screws. Be sure the rollers still move smoothly and look even. This gap setting will be right about 0.030 which I have my barley Crusher set to and I get 81% efficiency every single time I brew only barley based batches - being wheat is a much smaller kernel I've had varying efficiency and will be tightening my mill when I need to mill wheat.


Rev.
 
An interesting method for mill gap setting that I found on the Probrewers board.

Pass a short piece of brazing solder through the mill and then measure the total thickness of the deformed solder. The thickness values I've seen quoted from the pros that use this range from 1.6 to 1.9 mm. That reflects the depth of the valleys in the knurling as well as the roller offset.
 
mabrungard - that is probably a better way to measure anyways due to variations in knurling. Also, on some mills the knurling is more like spikes, that wear off over time.
 
Wow, thanks for all the help. There is no doubt that my mill is set incorrectly, I bet I could drop 2 credit cards between the rollers and they wouldn't even touch. I'm going to get a yeast starter up and running and brew sometime by the weekend to see how much these mill adjustments help my efficiency.

Thanks everybody,

Fred
 
Wfred - Good news/bad news:

Bad news is - there is no magic number for gap settting that works for everyone. Let's consider 3 different systems: barley crusher/rectangular cooler MLT w/braid; Corona Mill/keggle & false bottom; MM3 2.0 & blichmann 15 gallon button louvered false bottom.

Each of those systems will have different flow capacity (which drives husk integrity requirement) and each mill can only get so tight before it shreds the husks to oblivion. It's only logical that each system would need it's own gap setting.


Good news is, your mill is a piece of cake to adjust!

Id start with a credit card or feeler gauge if you have it. You need to get the rollers 100% parallel (each end of the rollers want to be the same space apart). If the rollers aren't aligned, it could lead to binding (esp at finer gaps) and uneven crush.

Once you have the rollers aligned, make tick marks on each side to mark this [starting] point. You can then loosen the thumb screws (these should never be more than finger tight) and begin the process of adjusting your mill.

I like to tighten the mill ever so slightly (the tick marks should barely deviate per each adjustment) and then tighten the thumb screws. Then I run about 1 cup of grain through and inspect the crush. Repeat this process until you can visually see that your husks are starting to lose their integrity.

You might want to have a pound or so of rice hulls on hand for your first session after the adjustment. If you went too fine, you might get a stuck mash and the rice hulls will be a life saver. If this is the case, simply go back to the mill and back it off a little - this adjustment will be very intuitive after your initial trial as you will be familiarized already.

People get so wrapped around the axle on some gap number as if someone else's setting is best for them. You have an adjustable mill - ADJUST IT! If there was a best number, mills would come pre-set that way haha.

Cheers,
~j
 
As Cmiyc stated, this is wrong. You don't need to mill it twice, simply tighten the gap. it's easy to do, you loosen the two set screws on the second (non-driven roller) side and adjust with the knurled knobs to move the roller closer. For now, if you don't have feeler gauges you can use an old credit card, I say old because the rollers will scratch the magnetic strip up. Tighten the knobs until they grip up against the card then tighten the screws. Be sure the rollers still move smoothly and look even. This gap setting will be right about 0.030 which I have my barley Crusher set to and I get 81% efficiency every single time I brew only barley based batches - being wheat is a much smaller kernel I've had varying efficiency and will be tightening my mill when I need to mill wheat.


Rev.

I was merely suggesting a quick fix to improve efficiency, I have used various mills of both two roller and 3 roller varieties and found the 3 roller crush to be more consistent over time, meaning that if your gap starts to spread you won't notice as much as you are basically milling twice already. Also .030 is probably too small a crush for some false bottoms, it's probably fine for kettle screens or manifolds but .040 is safer and you won't lose much efficiency.
 
PS: regarding that idea for passing solder through the mill. Don't use very large diameter solder since it could overload and damage the rollers. Use soft electrical solder and not silver solder since the electrical stuff is softer.
 
mabrungard said:
PS: regarding that idea for passing solder through the mill. Don't use very large diameter solder since it could overload and damage the rollers. Use soft electrical solder and not silver solder since the electrical stuff is softer.

And lead free solder, well unless you like heavy metals in your beer.
 
Keep tightening your gap until the husks don't look the way Kai says they should. Then loosen them back up until they do. This is probably going to be around .3 or the width of the pre-approved fake credit cards that barrage my mailbox,; but humidity, variation in grain size between years/maltsters/etc and other factors will change it a little for everyone.
 
FYI a credit card is .030. That's how I set my crusher. I use biab so I double crush. Last batch had 78% efficiency.

Here is my update:

I finally got a chance to brew, things got busy the last few days and I finally chiseled away 4 hours to brew.

I started out setting my mill using my costco card and crushed about a pound of grains. It looked like it was too fine, seemed to be very fine pieces in the bucket under the mill. I backed off the mill ever so little so the card would pass through without making a roller turn and then crushed the rest of the grains.

I followed my normal routine with a 60 mash, fly sparge, and 60 minute boil. The first few pitchers of wort and grain pieces in them but then it ran clear and I had no issues with the sparge sticking.

I brewed a vanilla porter that had a target OG of 1.055 at 70% efficiency. I took my OG reading and it was 1.076. It didn't appear to me that I over-crushed my grains and provided I don't have any off-flavors in my beer, I think I have my mill dialed in. The efficiency certainly responded the way I wanted it to.

Thanks again for all the help. I only hope that once I get to be a proficient enough brewer, I am able to repay the favor.

Fred
 
1.055 to 1.076 is a huge jump. I quickly tweaked my porter recipe in Beersmith to show 1.055 at 70% and to get a jump to 1.076, I'd have to hit 96-97% efficiency. Seems like you might have had something else going on also - like boiling it down for a lower volume (which increases OG).
 
1.055 to 1.076 is a huge jump. I quickly tweaked my porter recipe in Beersmith to show 1.055 at 70% and to get a jump to 1.076, I'd have to hit 96-97% efficiency. Seems like you might have had something else going on also - like boiling it down for a lower volume (which increases OG).

I collected 6 gallons of wort and boiled it for 60 minutes, i had a small amount of foam boil over, maybe a cup total. After I chilled it I added the wort to my primary fermenter and then added my 1L yeast starter and took my OG reading, that is how I take all my readings so I could compare to the dozens of other beers I have done. I had about a half inch short of 5 gallons in the primary so I added enough water to bring it up to 5 gallons. All said and done with 5 gallons, I probably was closer to 1.065 or 1.070.

Either way, I am stoked. Normally I would have had that beer around 1.045 if it was supposed to target and 1.055.

In another 4 or 5 months I will be able to know how it tastes.

Thanks again,

Fred
 
Once you have the rollers aligned, make tick marks on each side to mark this [starting] point. You can then loosen the thumb screws (these should never be more than finger tight) and begin the process of adjusting your mill.

Oddly enough, with my MM, i have to tighten the crap out of my thumbscrews. No matter how finger tight i get it the rollers will wander on me. Maybe I just need to dial it in better or something.
 
I dont have any issues with my mm-3 coming out of adjustment but I may have it cranked a little to tight since I set mine measuring peak to valley and have encountered a fair amount of binding which is a real pain.
 
Not to resurrect an old post, but does anyone have recommendations on mill speed? I use an MM2 as well and currently have the gap set to .035 but have been getting efficiency that is all over the board. Most of the time, my efficiency stays at 74%, but lately, my efficiency has been around 60-65%.

I power my mill with a corded drill that I run by attaching a clamp to the trigger. I try to run it at a fairly fast setting as I've heard the faster the mill, the finer the crush. Should I adjust my mill to a finer setting or slow down the drill?

It seems that most of my grain comes out cracked in half down the equator.
 
I run my MM-3 at about 250rpm and even with it gapped wide open I get a fine crush, perhaps a bit too fine as I see a fair amount of flour. Perhaps your variable efficiency is coming from somewhere else? Maybe the sparge would be a more likely culprit?
 
I power my mill with a corded drill that I run by attaching a clamp to the trigger. I try to run it at a fairly fast setting as I've heard the faster the mill, the finer the crush. Should I adjust my mill to a finer setting or slow down the drill?

Slow down the drill, ideally it should be running around 250 rpm, too fast can result in shredded husks.
 
I run my mill fast. After seeing how some breweries mill, I'm all about fast and fine. I've been consistently turning out 75-80% efficiencies.
 
I set the mill at the store using 3 NEW business cards. The gap when hit with feeler gages is always at .38 to .39 and I run a Faulk gearbox off an explosion proof 120VAC 1725 RPM motor. The mill is spinning at about 225 RPM. We have a great crush. 1 major complaint I do have about the MM2 is it is very hard to keep the gap set correctly. We check and adjust the gap every couple of days. Yes we are crushing tons of grain through it but I would think once "set" it should sit still!

Cheers
Jay
 
I had adjustment issues for a while now.
Last brew I cranked mine down until it wouldn't take grain into the mill rollers, (MM2). Then I backed the adjustable roller back out until grain started to run threw them. Then started to crank it back down to a finer crush. Got what I thought was a great crush and locked her down tight.

After reading this article, I check the spacing with a CC and it was a super snug fit. I'm totally tickled with this thread! :ban::ban:

I've got 2 x feeler gauges coming so I'm gonna be doing some checking. But so far I think the CC trick is cool for the .03 range.

Now just need some other handy shims for other thicknesses.

pb --- Where did I put my calipers?

Oh ya,... I ain't got any!!!
 
Anyone else have good information for a gap setting on a monster mill? I picked up a MM2 Pro and have it set at 0.036”. Also what I should look for as far as cracked grain.
 
I have an MM3 so my gap setting will be a different value than a two roller mill. I watched a video on YouTube that shows how to adjust the roller gap being mindful that the drive roller side adjustment is CC on my mill and the non-drive roller side adjustment is CCW (opposite) to tighten the gap. Once again, I watched a YouTube video that was helpful. Real feeler gauges are not expensive and help a lot to achieve the perfect setting. Interesting how folks will spend hundreds on a mill setup and wont spring for $5 on a feeler gauge to do it correctly.

If you BIAB you can grind finely, other AG process are not so grind flexible.
 
Anyone else have good information for a gap setting on a monster mill? I picked up a MM2 Pro and have it set at 0.036”. Also what I should look for as far as cracked grain.


What kind of brewhouse do you use?

Mill gap setting is a compromise between efficiency and your brewing set up. If you sparge you'll want it a bit more coarse if your BIAB you'll want a fine to very fine crush.
 
Although gap related, I am about to go off topic so I'll apologize to the OP upfront. :off: On the other hand, this is probably good info for the OP to see about mill settings.

If I set my gap on the MM3 for my typical BIAB grind with strictly barley malts, I'll get predictable efficiency results. If the combined grain bill contains a significant amount of wheat malts (with barley malts) and is run together, the efficiency drops like a rock due to the hardness and smaller size of the wheat kernel.

Do most brewers run the grains separately and adjust the gap differently (wheat tighter), or it is simply easier to add more wheat to the grain bill compensating for the efficiency loss you know you'll have by grinding together?
 
Off topic No. 2, and I am sorry, but hearing of these adjustment issues makes me question whether I should go to the MM at all....was going to pair it with the AAW 180 HP motor. 20 years ago I put tons of grain through a simple fixed JSP and drill and got excellent crushes. KISS?...
 
[...] If the combined grain bill contains a significant amount of wheat malts (with barley malts) and is run together, the efficiency drops like a rock due to the hardness and smaller size of the wheat kernel.

Do most brewers run the grains separately and adjust the gap differently (wheat tighter), or it is simply easier to add more wheat to the grain bill compensating for the efficiency loss you know you'll have by grinding together?

Yes, I mill small kernel grain (wheat, rye, flaked adjuncts, etc.) with a tighter gap. ~0.026" for those, vs. 0.034" for barley. That's on an MM2 (1.5" regular rollers).

That means I usually have to reset the mill gap once during a milling session.
[Edit] From what I understand on a 3-roller mill the gaps work a little differently, and isn't as simple to adjust.

If the small kernel grain doesn't get crushed well enough, their contribution will obviously lack.

Anecdote:
A few years ago during a beer judging class I had a wheat ale from a homebrewing couple. It tasted like no wheat was used! They were going to re-brew it, and when they returned from the LHBS' grain room, I asked for a peek in their bag of milled grain. Tons of whole wheat kernels! That explains it! I told them to remill it at least, or let's see if we can tighten that gap. Sadly, they ignored my advice and left with the bag as it was...
 
Last edited:
Off topic No. 2, and I am sorry, but hearing of these adjustment issues makes me question whether I should go to the MM at all....was going to pair it with the AAW 180 HP motor. 20 years ago I put tons of grain through a simple fixed JSP and drill and got excellent crushes. KISS?...

Honestly, I don't consider my situation an issue, rather it is more or less the nature of the beast grinding wheat along with barley. These grains are dissimilar in size and hardness which makes one "universal" grinding gap very difficult.

I built a motorized setup for my MM3 with the AAW 180 rpm motor and cannot be happier. You are well on the right track in my opinion.

FWIW, these mills can have a bit of learning curve understanding how achieve the optimal adjustment. I have used a cereal killer, a Kegco 3 roller and an MM3. I have picked these mills up along the way when I see a deal and it may come as part of a package from a brewer throwing in the towel.

But once you learn to set the mill correctly after some trial and error, it is not as intimidating as it sounds. Don't be discouraged as a properly dialed in mill makes your brewing experience most rewarding.
 
Yes, I mill small kernel grain (wheat, rye, flaked adjuncts, etc.) with a tighter gap. ~0.026" for those, vs. 0.034" for barley. That's on an MM2 (1.5" regular rollers).

That means I usually have to reset the mill gap once during a milling session.

If the small kernel grain doesn't get crushed well enough, their contribution will obviously lack.

Anecdote:
A few years ago during a beer judging class I had a wheat ale from a homebrewing couple. It tasted like no wheat was used! They were going to re-brew it, and when they returned from the LHBS' grain room, I asked for a peek in their bag of milled grain. Tons of whole wheat kernels! That explains it! I told them to remill it at least, or let's see if we can tighten that gap. Sadly, they ignored my advice and left with the bag as it was...

Gap setting can be painfully obvious when efficiency drops 15-20% as a result of grinding wheat (and other adjuncts) alongside barley. I'd say this 15-20% loss is a direct result of the wheat portion of the grain bill being poorly crushed. I plan to try resetting my gap and running the wheat separately to keep my efficiency percentages consistent.
 
Oh sorry, Morrey - I should have been clearer. I fully get the notion of different grains' needs. I was obviously being too lazy in reading the thread. I was talking of reading some things about adjustment drift and needing to re-calibrate every few days, much like a pH meter requiring same.

Off day, brain might as well be set to "steady state," so ignore this poster....:confused:

Thanks for your post however, - does help. OP, apologies.
 
Oh sorry, Morrey - I should have been clearer. I fully get the notion of different grains' needs. I was obviously being too lazy in reading the thread. I was talking of reading some things about adjustment drift and needing to re-calibrate every few days, much like a pH meter requiring same.

Off day, brain might as well be set to "steady state," so ignore this poster....:confused:

Thanks for your post however, - does help. OP, apologies.

Heck, no need to apologize as we are all in this together. The more we share our thoughts and process, the better we all become.

I haven't noted my MM3 being bad about coming off calibration. I have a sneaking suspicion folks may be grinding dissimilar grains together just as we are discussing now, then blaming the mill for gap drifting. The tough part of analysis is narrowing down the real fault and making the proper adjustment.

If a ph meter was made that never needed to be calibrated, I'd buy one today before the sun went down. LOL All good!
 
What kind of brewhouse do you use?

Mill gap setting is a compromise between efficiency and your brewing set up. If you sparge you'll want it a bit more coarse if your BIAB you'll want a fine to very fine crush.



Igloo cooler. Batch sparge.
 
[...] If I set my gap on the MM3 for my typical BIAB grind with strictly barley malts [...]

What is your "typical BIAB" gap?

I'm asking because BIAB grinds are usually quite a bit finer already than say, fly sparge grinds or even batch sparge grinds. At a BIAB gap I'm surprised that wheat not getting a decent crush. Do you see whole wheat kernels or large chunks of it?

Is that a 15-20% efficiency drop in recipes containing 40-50% wheat malt? If so, maybe a slightly tighter overall crush (and/or run through 2x) and a bit longer mash (add 15-20 mins) can fix that.
 
Ah, just thought of something, how do you sparge that bag?
Wheat (and rye, etc.) are very gummy. They make the grist hang on to a lot of wort and prevent thorough draining out.
 
What is your "typical BIAB" gap?

I'm asking because BIAB grinds are usually quite a bit finer already than say, fly sparge grinds or even batch sparge grinds. At a BIAB gap I'm surprised that wheat not getting a decent crush. Do you see whole wheat kernels or large chunks of it?

Is that a 15-20% efficiency drop in recipes containing 40-50% wheat malt? If so, maybe a slightly tighter overall crush (and/or run through 2x) and a bit longer mash (add 15-20 mins) can fix that.

Good questions. I set the gap between the top roller and bottom roller (MM3) to .037. The instructions suggest to start over .040 maybe up to .045 and evaluate the crush. I backed mine down slowly watching efficiency and feel .037 is a nicely fine BIAB grind for barley malts. Last beer used 40% wheat and the efficiency went way down which surprised me. Ph was stable at 5.30 15 min into the mash, I mashed at 150F on the money, even went 70 min vs 60 min mash. I think I am so familiar with the process I didn't really look closely at the grind....my bad. But for the sake of argument, I plan to keep the wheat separate and reduce my gap but keep the barley gap at .037. The wheat may be my first place to reevaluate.

***Let me add that I have established efficiency numbers with multiple lagers containing no adjuncts

Ah, just thought of something, how do you sparge that bag?
Wheat (and rye, etc.) are very gummy. They make the grist hang on to a lot of wort and prevent thorough draining out.

My sparges are pretty thorough. I have an Arbor Fab 400 uM basket with a press plate to fit. I'll pull the basket (pulley/chain) and press hard with the plate, then rough up the grain bed and pour 1/2 G of warm RO water over the grains to rinse sparge them. After pressing again, I am only absorbing 1/2 gallon of water in a 10# grain bill.

I know what you mean about wheat and rye sparges...they make a gummy mess. I honestly believe your original advice to mill the wheat separately with a reduced roller gap is going to bump my efficiency back where it belongs. I'll report back after my next beer (Hoppy Wheat w/Lemongrass) this weekend which is 50% wheat and 50% two row.
 

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