# Grain Mill - Not All Rollers Are The Same



## adama_bill (5/4/12)

Unless Ive missed it; Im surprised that there isnt more discussion about the difference in roller surface knurling from one mill to another. Most of what Ive seen written reads more like barracking than a discussion working through the designs on offer ~ this is especially the case for Monsters Mill vs. Crankandstein. Surely when you put aside the bling factor and get down to facts; the focus must be on 

1) roller diameter

2) knurling

3) rotation speed 

4) Metal hardness

5) feed chute arrangement 

6) (I guess you should/can also include Frame Rigidity, roller alignment method and_ heaps of other stuff as well_).

These toys are expensive and while Im sure they all do a good enough job, there has to be some reason why the (_for instance_) rollers on your homebrewing C&S have far more aggressive knurling than whats found on Monster Mill and MillMaster to name just a couple.

Ive seen it mentioned that the larger the diameter of the roller; the less the surface needs to be knurled because the rollers find it easier to squeeze open the grain. But generally speaking were talking about 1 inch vs. 2 inch diameter . . . can and inch make such a difference?

Admittedly I know nothing about this subject, but Im guessing that low profile knurling is a lot cheaper to manufacture than deep knurling . . . . hence thats why we see far more smooth bore rollers than otherwise? <_< 


Personally my main reason to get a mill is to make good beer; but I know that one day Ill also want to crack corn and other stuff to try and make some sour mash sippin juice .

If anyone can speak with authority about the above Id be more than happy to hear it. I have not found any back-to-back comparison that "weights up" the results achieved between strong knurling and mild knurling. I found one "commentator" that was prepared to say strong knurling (read C&S) is better but that's all. I'm not too swayed by seeing a particular brand showing in a lot of Brew Shop because for all I know, they could have had their mill heavily price discounted by the manufacture.


Currently all I can do is flip a coin to work out which way to go (and I sure as heck aint got enough coin to buy two mills).

Regards


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## Feldon (5/4/12)

Good strong post, Bill. You raise some interesting questions about the art and mystery of knurling. 
Can't help you myself, but I look forward to hearing what others might have to say. 
There's a lot of nous on this forum.


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## Online Brewing Supplies (5/4/12)

adama_bill said:


> Unless Ive missed it; Im surprised that there isnt more discussion about the difference in roller surface knurling from one mill to another. Most of what Ive seen written reads more like barracking than a discussion working through the designs on offer ~ this is especially the case for Monsters Mill vs. Crankandstein. Surely when you put aside the bling factor and get down to facts; the focus must be on
> 
> 1) roller diameter
> 
> ...


You raise some good points but ....Snip>"Admittedly I know nothing about this subject"," but I know that one day Ill also want to crack corn and other stuff to try and make some sour mash sippin juice" .<snip
Doh, you not approaching the subject in the right way. This is a brewing forum not a sippin juice chat show.
Ask the fitters on the forum what they think about knurling and they will probably tell you a good broom and a lump of ice.
Seriously, the engineering that goes into a good functional mill is more than you have mentioned.There are some good mills on the HB market, make your choice.
Nev


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## MHB (5/4/12)

There have been some good (if sometimes spirited) discussions about mill design threads here over the last couple of years. The theory that underpins crushing grain is called Nip Angle Theory, do all the numbers you like but what you end up concluding is:-
The bigger the rollers the better the crush
Two powered rollers is much better than one
The more wheels the better (the best mills have 6 rollers)
No 1 gap size is the right answer!
Knurling isnt really the best answer but fluting is too expensive 
The more wheels the better (the best mills have 6 rollers) but 2 will do for home brewers

For the money I think the best available is the Mash Master (dont have one nor do I sell them) the combination of decent sized and powered rollers should give the best possible crack for a small scale mill. To my mind the biggest improvements in this mill would come from getting the gears outside the mill body and making the gap adjustment easier; double ended eccentric really is the industry standard.
If I was buying a mill I would opt for the Stainless Steel version (I know its around $500) a once in a lifetime investment.
Mark


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## adama_bill (6/4/12)

> There are some good mills on the HB market, make your choice.
> Nev


*Well that's no help at all.*



> The bigger the rollers the better the crush
> Two powered rollers is much better than one
> The more wheels the better (the best mills have 6 rollers)
> No 1 gap size is the right answer!
> ...


Thank you for taking the time to list the pertinent design priorities; that's exactly what I'm wanting to read. Some back-to-back evidence would be great if anyone has any.
​*Summary of choices in standard mode:*

*MM2-2.0*($171 + $50 postage )

Has the bigger 2inch rollers ~ only one powered
Has broad gap range: 

"0 to 4.06mm; more than double our standard range"
"that should allow you to mill other grains like corn, as well as the conventional grist bills with barley"

*MillMaster MiniMill* ($249 + postage)

304 Stainless Steel Rollers as Standard ~ 1.5 inch diameter 
Gear Driven Rollers
adjustable gap is 0.1mm to 1.9mm
*C&S 3E* ($144 + $48 postage)

Has 3 rollers ~ 1.5 inch diameter 
"with grain-engaged gear teeth at ends on the upper rollers" ~ that sounds the same as "_Gear Driven Rollers_"
adjustable gap is 0.25mm to 1.77mm
I'll procrastinate on this for another couple of weeks (and pay my current bills).
The _biggest and the best_ would be great but I'm close to retirement and my children show little interest in the hobby . . . . so as always I'll try to make the best overall choice ~ I don't drink that much anyway.

Thanks for the grey-matter input; that's certainly better than rooting from the bleaches.

Regards


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## ekul (6/4/12)

I have a MM2, works great. Not sure if it would crush corn or not, never tried.


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## fraser_john (6/4/12)

adama_bill said:


> <snip>
> "with grain-engaged gear teeth at ends on the upper rollers" ~ that sounds the same as "_Gear Driven Rollers_"[/size]
> <snip>



No, this is not gear driven rollers. I have the 3D model. The "grain engaged gear teeth" are just a bit of different knurling (some fitter can attest to the type of knurling) at one end of the rollers that is parallel to the length of the roller, it gives the rollers an easier chance to get started as grain fits into the knurl easier.

Probably does not make one iota of difference really.


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## Sammus (6/4/12)

adama_bill said:


> [*]"with grain-engaged gear teeth at ends on the upper rollers" ~ that sounds the same as "_Gear Driven Rollers_"



Yep, as above, "grain driven roller" is the exact opposite to gear drive roller. Gear driven means both rollers spin at the same speed at the same time, all the time, even when it's empty. Think of two gears or cogs meshing with each other, and one turning; so does the other one. Grain driven is basically a fancy way to say they skimped on such a useful feature, and in fact only one roller is connected to the motor/crank, and the other free roller will be forced to spin once there is a piece of grain wedged between it and the driven one.


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## iralosavic (6/4/12)

It's great to be able to make a thorough specification comparison before making a purchase, but unless you're happy to take the manufacturer's marketing drivel as gospel or the testimonial of other home brewers as good enough, you may just have to accept that doing your own research will take considerable effort on your own part - and sometimes it's simply not feasable to expect to be able to fully comprehend every fascet of the more technical aspects behind product design.

My personal approach is to research to the point where I fully understand all the principals that within my ability to comprehend in a reasoanble time frame (ie I don't need to get a degree in engineering first) and then compare my results against what the far more experienced brewers around here use. After all, if a room full of blokes on here have crushed tonnes of grain each and can still recommend their mill in a heart beat, who am I kidding - that's good enough for me! It's just a matter of doing some ground-work first so you can narrow down the specific choices available.


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## MHB (6/4/12)

You would need a 4-5mm gap to crack corn as well as a shed load of power; you can buy cracked corn from any animal feed stockist for about the same price as whole corn, having said that it isnt beer brewing grade corn.
Same applies to malt, most HBS will crack for free and if your HBS is any good they should have a better mill than any most home brewers can afford and ideally should crack the malt the way you want it.


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## fraser_john (6/4/12)

A little :icon_offtopic: but.....

If planning on using cracked corn for brewing beers......corn contains a large amount of oil/fats. The flaked maize you buy already has this removed.

I used my own home grown corn in a CAP and it resulted in a massive ball of oil/fats in the fermenter, I'd guess taking up about 15% of the carboy volume, strangest thing I have ever seen. I ended up racking most of it out, but it resulted in a lower volume of beer as it was kind of emuslified with the wort.

I think I have a picture of it somewhere.....


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## QldKev (6/4/12)

I'll give you my opinions on these. 

Besides having a mm2 for a few years, and seeing a few other mills in use, I don't have any additional grain mill history.
I have seen these two mills, here , with the larger one in action many times. (the smaller 89mm roller one is yet to be used) (The pic comparing it to the mash master is a full size mashmaster, not the new mini model)
I did work in the sugar industry for a few years ad asked too many question about their mill setups, but they crush sugar cane not grain.


My responses will run into each other because they are inter-related

1) roller diameter

The larger the roller, the less the entry angle. This will help give a better crush. While 0.5" will make a difference I don't think it makes much of a real world difference.


2) knurling

Knurling is great for dragging grain into the mill, but from my understanding is actually bad for the crush itself. If you could get a smooth roller to efficiently draw grain, then it would reduce tearing. Smooth rollers do not want to draw grain nicely, and any grain slipping on the surface of the roller causes ripping/tearing of the husk, hence is bad. Larger rollers with the reduced entry angle require less knurling without slipping. 

3) rotation speed 

You want a consistent speed within the correct rev range for the mill. This is directly proportional to the mill roller diameter. The larger the diameter the higher the surface of the rollers is moving. I've been told anywhere from 250mm to 500mm is the best speed for the grain feed for the size rollers we use. Larger roller sizes although increase this grain speed, do have the lesser feed angle and can often be pushed faster. Also 3 rollers mills flatten the grain on the first set of rollers, and then crush on the second set of rollers; also allowing a faster mill speed. Unless you want to crush a lot of grain, there is no need to push it fast and staying in the lower end of the speed range I think is best. 


4) Metal hardness

I think all commercial mills are hard enough for what we use them for. The main advantage of the harder rollers is the life expectancy. I believe all mills mentioned should last many good years of crushing. I have put over a tonne of grain through my MM2, and it looks as good as the day I got it. 

S/S is an option on many mills. Some people complain of non s/s rollers rusting. I don't have a s/s roller setup, and know 3 brewers (including myself) who live close to the beach and are not having issues with rust on the rollers. I purposely leave the flour on the rollers at the end of crushing as a protective barrier. 


5) feed chute arrangement 

Some offer a option to purchase a ready to assemble setup. My setup was a real quick and dirty wooden feeder that was going to be a temporary setup. It holds a decent amount of grain, but I need to use a paint brush to push the last of the grain through. So far I'm happy, it does the job with it and have no short term plans of changing. To me as long as it has a reasonable capacity, and it not too restrictive feeding the grain, it's just a feed chute. (pics on my website under mill)



6) (I guess you should/can also include Frame Rigidity, roller alignment method and_ heaps of other stuff as well_).

Some mills have rollers mounted into a rigid frame, which makes mounting / aligning the rollers easier. Over the years I've read a few times where people complain about their mm* mill is not feeding grain, which normally comes back to the mounting. Either they are not mounted square, of the end plates are too far apart allowing grain to become wedged into the non-driven roller ends. It took me 2 attempts to get a nice perfect mount of mine, but it has since been in service for years with no dramas. The easy test is to try and spin the non-driven roller, if it spins freely all is ok. 


Another aspect is the driven second rollers. This helps by ensuring both rollers are twisting with equal force on the grain husk to help reduce tearing. While I do think it helps, especially when the grain is first fed, I don't think it is a necessity. Once you have commenced a a crush and the non-driven roller is up to speed it does not take much effort for it to continue at the speed. 

The 3 roller mills allow the first set of rollers to feed the grain under a slightly reduce gap size, this helps squeeze the grain and soften the husk. On some mills these feed and top rollers are fixed spacings so cannot be adjusted. It also provides a positive feed onto the third discharge roller, hence it allows the 3rd roller to be a smooth roller for the crushing (remember before I mentioned that is a good thing), but the 1st feed roller is still involved in the crush so you gain the full benefit. 

Finally question is how to power the mill. Hand crank, drill or motor. I've never hand cranked, but I imagine on the down stroke the use would exert more pressure then on the up stroke of the crank handle, giving a continuous change in torque resulting in a less even crush. I used a drill for 18months in low it had a 0-350rpm range, I found it hard to keep in the correct rev range all the time, especially with the larger sized crushes I do (15kg is normal in 1 crush). I'm now running a motor (ref my website) which I think has improved my crush quality from the drill due to a uniform torque output within the correct rev range. It's also a lot easier for me to fire up the mill and do other things. 


Overall I think any of the mills you picked should give many years of good crushing.


QldKev


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## Fish13 (6/4/12)

At The flour mill i used to work at they used two rollers with one spinning faster and fluted. They cut the grain lots better then crushing.


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## Online Brewing Supplies (6/4/12)

adama_bill said:


> *Well that's no help at all.*


My money is on the Mash Mater mill.
Nev


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## fraser_john (6/4/12)

:icon_offtopic: Continuing on the off topic, but somewhat related to crushing corn part of this thread



fraser_john said:


> I think I have a picture of it somewhere.....



Home grown corn in a CAP, note the "oil ball"

And here it is...


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## adama_bill (6/4/12)

You may be interested in the text below about metal hardness; it was posted by *Irrenarzthttp://iam.homebrewtalk.com/Irrenarzt *on another forum on 11-14-2011, 04:57 PM 

>>>>>>>>>>>>>>>>>>>>
I'm not a metallugist by any means but I have a masters degree in Chemical Engineering so I suppose I'm close to qualified to answer.
303 Stainless is relatively soft. It's primarily used as a "machinable" grade of stainless as 304 and 316 give machinists a hard time to machine relative to 303. The real advantage of 303 SS is that it won't corrode. 
Otherwise _I think it will wear much faster than the 1144, especially if it is case hardened (heat treated). _
Here's a summary of each material from a site I found.

*STAINLESS TYPE 303*
Type 303 is highly corrosion resistant & non-magnetic.
It has non-galling & non-seizing qualities which allow for easy machining & is better for lighter equipment if welding is not required.
When cold worked - can become slightly magnetic.
Free machining for heavier cuts in automatic machining operations.
Corrosion resistant to atmospheric exposures, sterilizing solutions, most organic & many inorganic chemicals, most dyes, nitric acid & foods.
Machinability is 70% (1212 crs = 100% & 1018 crs= 78%.
Non magnetic.

*STRESSPROOF C1144*
C1144 is made by a patented process which consists of drawing the bar through a special die under heavy draft, then stress relieving it in a precisely controlled furnace.
Users can now get wearability without case hardening, strength without heat treating, plus excellent machinability & tool life.
Other benefits include resistance to fatigue & stress, balanced working & minimum warpage & distortion.

>>>>>>>>>>>>>>>>>>>>

Regards


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## Newts (3/11/13)

Hey, the search function worked! Just thought I'd ask if anyone actually had some results from this? Has anyone had a go at cracking corn with any of these mills and if so did it work? Have a friend that has horses and was looking at getting a grain mill to crush corn etc. Asked if he can use my Mashmaster Minimill but looks like it won't work anyway with the smallish gap. Not sure I'd want animal feed going through my mill but might not do any harm either.

Any thoughts?


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## tavas (3/11/13)

adama_bill said:


> You may be interested in the text below about metal hardness; it was posted by *Irrenarzthttp://iam.homebrewtalk.com/Irrenarzt *on another forum on 11-14-2011, 04:57 PM >>>>>>>>>>>>>>>>>>>>I'm not a metallugist by any means but I have a masters degree in Chemical Engineering so I suppose I'm close to qualified to answer.303 Stainless is relatively soft. It's primarily used as a "machinable" grade of stainless as 304 and 316 give machinists a hard time to machine relative to 303. The real advantage of 303 SS is that it won't corrode. Otherwise _I think it will wear much faster than the 1144, especially if it is case hardened (heat treated). _ Here's a summary of each material from a site I found. *STAINLESS TYPE 303* Type 303 is highly corrosion resistant & non-magnetic. It has non-galling & non-seizing qualities which allow for easy machining & is better for lighter equipment if welding is not required. When cold worked - can become slightly magnetic. Free machining for heavier cuts in automatic machining operations. Corrosion resistant to atmospheric exposures, sterilizing solutions, most organic & many inorganic chemicals, most dyes, nitric acid & foods. Machinability is 70% (1212 crs = 100% & 1018 crs= 78%. Non magnetic. *STRESSPROOF C1144* C1144 is made by a patented process which consists of drawing the bar through a special die under heavy draft, then stress relieving it in a precisely controlled furnace. Users can now get wearability without case hardening, strength without heat treating, plus excellent machinability & tool life. Other benefits include resistance to fatigue & stress, balanced working & minimum warpage & distortion.>>>>>>>>>>>>>>>>>>>>Regards


Hardness of both metals is about the same. Hardness for 303 stainless is 228 Brinell vs 217 for C1144. Within a nat's doodle of each other. Both will probably outlive most people's interest in the hobby.


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## browndog (3/11/13)

Newts said:


> Hey, the search function worked! Just thought I'd ask if anyone actually had some results from this? Has anyone had a go at cracking corn with any of these mills and if so did it work? Have a friend that has horses and was looking at getting a grain mill to crush corn etc. Asked if he can use my Mashmaster Minimill but looks like it won't work anyway with the smallish gap. Not sure I'd want animal feed going through my mill but might not do any harm either.
> 
> Any thoughts?


Don't put corn through your mill, it's not designed for it. Even unmalted wheat gives mills a hard time. I dread to think what corn would do it it if you could ge the gap wide enough.


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## [email protected] (5/11/13)

Hey Newts,

Most animal feed, and especially corn because of its size, is done in a hammer mill. I saw one on gumtree a few days ago was about the size of a cement mixer and would be ideal for what your friend wants.


Cheers,

Andrew.


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