How Commercial Flour Mills Work

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Flour milling is an essential part of the process for creating and mass-producing all varieties of flour. Since flour is the bedrock ingredient of a large majority of the foods eaten across the world, the ability to mill, mix, grind, and package flour must be undertaken by commercial flour mills in order to produce flour rapidly. From milling machines to disc separators, augers, and screens, how exactly do commercial flour mills work?

Commercial flour mills are is large centers that specialize in the breaking down of various types of wheat into various types of flour. The main machinery used in commercial flour mills are industrial flour mills. These machines grind flour into a fine, powdery substance that can then be used for baking purposes and recipes. 

You may already know how flour is made, but there are also some important and interesting details to keep in mind about the commercial flour mill process. Since flour is a cornerstone of dietary importance in the modern world, commercial flour mills are well-oiled, expertly run industries that mass produce flour to meet the demand and necessity of its need. Read on to find out all about commercial flour mills. 

How Commercial Flour Mills Work: Step by Step

Commercial flour mills have the process of creating flour down to a literal science, but even though the process is completed on a massive scale, with loads of equipment, it is still fundamentally the same; rather processing a bag of wheat or a large truckload. 

The first stage is to completely wash the wheat or other grain. Because foreign materials like little rocks, stones, seed or other material are usually always brought along with the harvest. If the wheat is not clean, it may cause damage to the flour mill machine. Then the washed product is passed through an aspirator to suck clean any substance that is less in weight than the wheat grain and could have escaped the first cleaning stage.

electrical mill machinery

Through physical and chemical grading analysis, sampling the cleaned wheat according to their protein content and those with the highest level mix together to produce high quality wheat flour.

After processing the wheat through the flour mill, we can get different classes of wheat flour. They are classified according to their protein content and usage.

In the flour mills production process great precautions are taken to ensure that the best flour grade is produced. Every process is conducted by a qualified team who ensures that high levels of hygienic measures are taken.

Here is a step-by-step process of how a mill works.

Analyzing the Chemical and Physical Grading

In this step, the samples are cleaned of what is used for chemical and physical grading analysis. Then, they are arranged as per their protein content. Later, the ones with the highest protein level are mixed to produce the top-grade wheat flour. 

Milling the Wheat Flour

The wheat grains are then milled by passing them through the flour milling machine’s two giant metal rollers, often known as the breaker rolls. The breaker rolls help open up the what grain by separating the outer layer from the inner components. The grinding stage of the flour milling process produces three levels of elements as an end result, they are:

  • The Farina, i.e., the finest substance
  • Semolina, i.e., the interior largest shreds
  • The parts attached to the bran.

These end products are sorted and milled again, following the same procedure to produce various flour grades. 

Every step in the flour mill production is administered and managed by a qualified team of professionals who ensure that the highest hygienic measures are followed. 

Moreover, these flour mill production processes help to ensure the finest grade of flour. 

So How Do Commercial Flour Mills Work?

In commercial flour mills, the grain is refined and then softened, which means that the grains are soaked in water to increase the moisture content to roll easier inside the machine. After tempering, the grain particles are passed through a series of rollers that break the grain into three different parts like bran, endosperm, and germ. Each section produces a distinct type of flour, varying in the matters of textures and properties. 

The Final Products Obtained

  • White Flour – This flour is obtained from the early rolls. In the later rolls, the amount of bran particles increases, making the flour less white. 
  • Brown Flour – This type of flour is a mixture of white flour and the other streams. 
  • Wholemeal Flour – When all the different streams are mixed in their original volumes to produce this type of flour. The leftover brans and materials are then usually used for fodder or breakfast cereals. 
  • All in all, the production of flour types is influenced by the quality of grain entering the flour milling machine. 

Take a look at this video to see the entire process in action:

Now, What Exactly Is the Function of a Flour Mill?

The function is essentially the same, but it does vary widely depending on the grain.

The most generally consumed types of grains are legumes and cereals. Legumes like beans, soybeans, peas, lentils, and peanuts are required to be processed to transform into consumable goods. However, they do not require to be broken down, unlike the cereal grains. Due to the physical composition of cereal grains like wheat, rye, barley, they need to be broken down by grinding machines to produce end products like flour. 

Flour mills are used to grind and break down the grains into smaller pieces and separate them. Depending on your requirements, you can choose from the wide range of sizes available in the market. For domestic uses, you can go for the table-top and kitchen flour mills. If you plan to start your own atta chakki or already own one, you have to choose from the commercial versions, which is something to be aware of when wanting exotic flours. 

The function of all these machines is similar, the significant difference being in their volume. 

Commercial flour mills play a very vital role, especially in the agricultural industry. Since they can perform the task of milling in a lesser time than the laborers and with more accuracy, the general public can easily access the grains at an affordable price. 

With the use of flour mills, the process of grinding the grains becomes much simpler and more accurate. All in all, the steps mentioned above are followed to grind grains like cereals and pulses using the flour mill machines. 

What are the Major Steps in Milling Flour?

As mentioned above, the milling process is the most important, but what exactly is involved in milling? Let’s take a deeper dive into this process. 

Milling of wheat is the process that turns whole grains into flours. The overall aims of the miller are to produce:

  • A consistent product
  • A range of flours suitable for a variety of functions
  • Flours with predictable performance

The very first mill operation is analyzing the grain, which determines criteria such as the gluten content and amylase activity. It is at this point that decisions about blending are made.

Following analysis, milling may be divided into three stages:

  • Cleaning and conditioning – ridding the grain of all impurities and readying it for milling
  • Crushing or breaking – breaking down the grain in successive stages to release its component parts
  • Reduction – progressive rollings and siftings to refine the flour and separate it into various categories, called streams
Agro-processing plant

Cleaning Explained

Wheat received at the mill contains weeds, seeds, chaff, and other foreign material. Strong drafts of air from the aspirator remove lighter impurities. The disc separator removes barley, oats, and other foreign materials. From there, the wheat goes to the scourers in which it is driven vigorously against perforated steel casings by metal beaters. 

In this way, much of the dirt lodged in the crease of the wheat berry is removed and carried away by a strong blast of air. Then the magnetic separator removes any iron or steel.

At this point, the wheat is moistened. Machines known as whizzers take off the surface moisture. 

The wheat is then tempered, or allowed to lie in bins for a short time while still damp, to toughen the bran coat, thus making possible a complete separation of the bran from the flour-producing portion of the wheat berry. After tempering, the wheat is warmed to a uniform temperature before the crushing process starts.

Crushing and Breaking Explained

The objectives at this stage of a commercial flour mill are twofold:

  • Separate as much bran and germ as possible from the endosperm
  • Maximize the flour from the resulting endosperm

Household grain mills create flour in one step — grain in one end, flour out the other — but the commercial mill breaks the grain down in a succession of very gradual steps, ensuring that little bran and germ are mixed with any endosperm.

Although the process is referred to as crushing, flour mills crack rather than crush the wheat with large steel rollers. The rollers at the beginning of the milling system are corrugated and break the wheat into coarse particles. The grain passes through screens of increasing fineness. Air currents draw off impurities from the middlings. Middlings is the name given to coarse fragments of endosperm, somewhere between the size of semolina and flour. 

Middlings occur after the “break” of the grain.

Bran and germ are sifted out, and the coarse particles are rolled, sifted, and purified again. This separation of germ and bran from the endosperm is an important goal of the miller. It is done to improve dough-making characteristics and color. As well, the germ contains oil and can affect the qualities of the flour.

Reduction Explained

In the reduction stage, the coarser particles go through a series of fine rollers and sieves. After the first crushing, the wheat is separated into five or six streams. This is accomplished by means of machines called plansifters that contain sieves, stacked vertically, with meshes of various sizes. The finest mesh is as fine as the finished flour, and some flour is created at an early stage of reduction.

Next, each of the divisions or streams passes through cleaning machines, known as purifiers, a series of sieves arranged horizontally and slightly angled. An upcurrent draught of air assists in eliminating dust. The product is crushed a little more, and each of the resulting streams is again divided into numerous portions by means of sifting. 

The final crushings are made by perfectly smooth steel rollers that reduce the middlings into flour. The flour is then bleached and put into bulk storage. From bulk storage, the flour is enriched (thiamine, niacin, riboflavin, and iron are added, which gives flour-based products extra nutritional value), and either bagged for home and bakery use or made ready for bulk delivery.

Extraction Rates: An Overview

If you are like me, you are not so great at mathematics. But the extraction rate for commercial flour milling is crucial to the product’s overall conditioning.

The extraction rate is a figure representing the percentage of flour produced from a given quantity of grain. For example, if 82 kg of flour is produced from 100 kg of grain, the extraction rate is 82% (82÷100×100). Extraction rates vary depending on the type of flour produced. 

A whole grain flour, which contains all of the germ, bran, and endosperm, can have an extraction rate of close to 100%, while white all-purpose flours generally have extraction rates of around 70%. Since many of the nutrients are found in the germ and bran, flours with a higher extraction rate have a higher nutritional value.

What Force Runs a Flour Mill?

In addition to basic gravity, there also has to be a “force” by which to mold the wheat or similar substance into a flour. Post-harvest activity can be critical in helping farmers increase their income. For activities like milling, pressing, cutting, and shredding, Improved water mills can have an 80–90% increase in power use and efficiency compared to a traditional water mill. 

They can also have multiple uses such as for both agro-processing and power generation, which can increase the load of the mill and make such installations more sustainable. The mill and its machinery are powered by the force of gravity as water pours over the water wheel and causes it to turn. 

The main shaft of the water wheel enters the mill in the basement, where a complex assortment of oaken gears and shafts mesh together to power machinery located on all four floors of the mill. Originally, about 60 to 70 percent of the power was used to turn the millstones that grind grain into flour; the rest of the energy went to the other grain- and flour-processing equipment positioned throughout the mill. 

Not all of that equipment has yet been restored to operating condition. The long-term goal of the Department of Agriculture is to see that the entire system can once again operate as it did when the mill’s first restoration occurred in the 1930s.  Originally, grain was brought into the mill on the first floor and dumped into the receiving hopper that stands just inside the front entrance. 

Flowing down to the basement through a wooden chute, the grain was then lifted by an elevator to the top (attic) floor of the mill. The mill’s elevators are narrow enclosed chutes that carry the grain in metal cups affixed to leather belts. In the attic, the grain then passed through a double-mesh grain cleaner, essentially a large sifter designed to remove sticks, pebbles, and other foreign matter, thus ensuring that only pure grain would continue on for grinding. 

That grain then descended through more chutes to storage bins on the second floor, where it waited to drop into hoppers positioned just above the millstones on the first floor. While the machinery for this process is in place, it is not currently operational. Until it is restored, the current miller bypasses the grain cleaning process by pouring already-clean grain directly into the hopper over the millstones. 

Grain is fed in at the center of the running stone, and the turning of the stone shears the grain without crushing it. Centrifugal force carries the cut grain, called meal, through chiseled grooves in the bed stone to the rim of the millstones, where it is collected in a vat and funneled down to the basement.

What Exactly Happens to Wheat During the Milling Process?

wheat grains

The wheat flour milling process begins after the wheat is harvested and is delivered to local elevators where it is graded and sold. The wheat is then delivered to the flour mill, where the first step is to remove the dirt and impurities. The wheat kernels pass through a series of rollers and sieves and are thoroughly cleaned. 

Additional rollers are used to break the kernels to expose the endosperm, which is the portion used for white flour. Another series of rollers crushes the endosperm and a set of sieves removes the residue (chaff) of the kernels. The crushed endosperm is sieved until it is in the form of a fine powder. Rolling and sieving continues to produce various types and textures of flour.

As mentioned, during the early days of commercial flour milling in the United States, wheat was milled with traditional heavy, flat stones (millstones), which were excellent tools for grinding grain, however the flour was usually discolored due to the buildup of heat from the millstones. In addition to this, particles of bran were distributed throughout the flour and the flour did not have a long shelf life.

New techniques were developed that allowed the bran to be separated from the wheat kernel in order to produce cleaner, whiter, and finer textured flour. Chilled rollers, constructed of porcelain or iron, were used to grind the wheat so that heat did not build up. Because the nutrient-rich bran and germ are removed when producing white flour, it is often enriched with vitamins and minerals to replace the missing nutrients.

The use of steel grinding equipment for milling wheat is a common procedure for mills that produce large volumes of flour (known as steel-ground flour) for commercial use and retail sales. The wheat germ and bran are separated from the remaining portion of the kernel automatically, but are returned to the flour later in the milling process to produce the whole-wheat flour. 

Small quantities of bran and germ may be lost during the process, however when wheat is milled with the traditional method of cold grinding between heavy millstones, no part of the wheat kernel is lost or separated. Many people regard stone ground wheat flour as the most flavorful and nutritious.

Many types of wheat flour are available in bleached and unbleached varieties. Wheat flour becomes white (actually off-white) naturally through oxidation, which in earlier times was the method used by flour millers to create white flour. This eventually became impractical because of the time and space required for large quantities of flour to oxidize naturally so chemical bleaching was developed, which hastens the whitening process. 

The chemicals used for bleaching flour (usually chlorine, which evaporates after it is added to the flour) act as a preservative so that the flour will not develop an off flavor or spoil after a short period. The chemicals also prevent dough from becoming discolored and provide more consistent results when baking, however the chemicals affect the gluten strength of the flour, therefore bread makers often prefer unbleached flour.

“Kernel” is the wheat seed that is grown from the wheat plant. Most of the wheat plants grow up to two to four feet. The wheat head is harvested to produce food and each plant can yield 50-75 kernels. These kernels are small, dry, and suitable for storage and transportation. Then, they are milled into the floor, and this process is known as ‘wheat milling’.

What are the Steps Involved in Wheat Milling?

The wheat milling process involves separating the wheat grain into three constituents – germ, bran, and endosperm. It is a complex and intricate process. Once the wheat is prepared it is weighed, inspected, and graded. Then, the grain is separated by size, shape, and weight.

Step 1: Cleaning

sticks, stones and other such impurities are removed from the wheat. Then, the whole pure wheat is passed for further processing into the conditioning bins.

Step 2: Tempering and conditioning

At this stage, the wheat is soaked in water to easily remove the bran. Conditioning is done before milling to ensure moisture content is uniform throughout the grain. The moisture helps prevent the bran from breaking during the milling process.

Step 3: Gristing

This is a particularly important stage where the conditioned wheat and cleaned wheat are mixed to create the required type and quality of flour.

Step 4: Separating

The grist then goes through a series of rolls which rotate at various speed levels. The rolls only split the wheat grain open to separate the inner white portion from the bran.

Step 5: Milling

The wheat is grounded by a machine that crushes it into pieces. It is then put through sifters from which the meal obtained is processed further with repeated grinding and sifting. Then, the meal becomes fine flour, wheat germ and wheat bran.

Step 6: Blending

Here, constituents are mixed to produce different flours. For instance, a blend of wheat bran and white flour produces whole wheat flour.

The types of flour:

Early rolls produce white flour that becomes less white on the later stage, with the increased amount of bran particles. A mixture of white flour and other streams produces brown flour When all the other streams are mixed back in their original quantities you get wholemeal flour.

It should be noted that the flour types to be produced are affected by the different qualities of wheat going into the mill. 

While milling, one must ensure further feature variations such as flour color by mixing various streams of flour together.

Finally, the mill ends up with wheatgerm, or pollard which is fine bran and flour. Mills can then either package these products or sell them as bulk supplies. Mills can also add value to their product by making flour into self-raising flours, pastry flours,and premixes.

All these are produced by using flours from different parts of the system and in some cases adding additional ingredients.

Parts of the Milling Process Explained

commercial milling process

Let’s take a closer look at each part of the milling process and the materials used to produce flour into its final state:

  • Grain Cleaning / Vibrating Screen: Grain is removed of various types of impurities together with damaged, shrunken and broken kernels which are collectively known as screenings. This removes bits of straw and other coarse materials and the second screen removes foreign materials like seeds.
  • Aspirator: It lifts off lighter impurities in the wheat. The stream of grain is directed across screens while air sucks off the dust and lighter.
  • Disc separator: After the aspirator it moves into a disc separator consisting of discs revolving on a horizontal axis. The surface of the discs is intended to catch individual grains of wheat but reject larger or smaller material.
  • Scourer: The wheat then moves into the scourer, a machine in which beaters attached to a central shaft throw the wheat violently against the surrounding drum, buffing each kernel and breaking off the kernel hairs.
  • Magnetic Separator: The stream of wheat next passes over a magnetic separator that pulls out iron and steel particles contaminated during harvesting.
  • Washer stoner: high-speed rotators spin the wheat in the water bath. Excess water is thrown out by centrifugal force. Stones drop to the bottom and are removed. Lighter material floats off leaving only the clean wheat.
  • Tempering: Wheat is tempered, before the start of grinding, the process in which moisture is added. Tempering aids in separation of the bran from the endosperm and helps to provide a constant controlled amount of moisture and temperature throughout milling. The percentage of moisture, length of soaking, time and temperature are three important factors in tempering with different requirements in soft, medium and hard wheat.
  • Entoleter: Discs revolving at high speed in the scourer aspirator hurl the wheat against finger-like pins. The impact cracks down any unsound kernel which is rejected.
  • Grinding bin: The “first break” roles of a mill and are corrugated rather than smooth, break into coarse particles.
  • Sifter: The broken particles of wheat and bran go into a box like sifter where they are shaken through a series of cloth or screens to separate larger from the smaller particles. Larger particles are shaken off from the top by leaving the final flour to shift towards the bottom.
  • Purifier: The top fractions and particles of endosperm graded by size are carried to separate purifiers. In a purifier a controlled flow of air lifts off bran particles while cloth screen separates and grades coarse fractions by size and qualities.
  • The down purifier: Four or five additional break rolls with successively final corrugations and each followed by a sifter are usually used to rework the coarse stock from the sifter and reduce the wheat particles’ granular middling’s as free from bran as possible. Sifters, purifiers and rollers reduce wheat until the maximum amount of flour (72.0%) is separated.

How Do Flour Mills Grow Business?

Commercial flour mills constantly need to create new and efficient ideas in order to stay profitable and stand out amongst competition. 

One such recent process to achieve this is the use of the roller flour mill, which is a process industry to mill the grains and provide the endosperm as various fractions like maida, sooji, and atta. The skin or bran is separated from the endosperm and sold as cattle feed in this process.

These products have sufficient domestic demand. Additionally, there are export potentials also. Generally, atta, maida, suji, and corn flours are the basic ingredients for a wide range of processed foods. 

Commercial flour mills grow their business primarily in these ways. And the different business models demand different infrastructure and investment.

Cost of Setting Up Commercial Flour Mills

Flour milling business generally demands two different types of investments. One is a fixed capital investment. It includes land (if you purchase the land), building, machinery, registration, and licensing fees. If you start the business with a rental premise then fixed capital includes the security deposit amount for the area of land.

Another is the working capital investment. It includes raw materials, staffing, rent, transportation, marketing, distribution, and administration costs. There are different types of small business loans provided by companies in our country. And loan providers also offer various customized schemes for your specific requirements.

Flour Mill Profit Margin

You can earn an inspiring profit margin from a flour milling business. However, the percentage of profit depends on several aspects. For enhancing the profit, you will need to reduce the production cost.

Also, you must consider enhancing the sales volume and penetrating new areas. Always remember, you will only expect a good profit when you sell the product as a brand.

Flour Mill Business Plant Setup and Machinery

First of all, you have to secure a location for manufacturing operations. Check the available transportation facility, electricity, water, semi-skilled manpower, and drainage facility. For setting up a small scale unit with the entire product range, you will need to have 3000 square foot built-up areas at least.

The production process for each item is a little bit different. You can source the manufacturing technology from the Department of Agriculture in exchange for certain fees. 

Can You Grind Your Own Flour?

Commercial flour mills are not the only way to attain flour as you can certainly grind your own flour at home.

Flour milled at home is healthier and fresher, plus it can have a much more distinctive and immediate taste when compared to packaged flour from a mill.

Do you ever wonder about the flour you purchase from the store? I frequently used to wonder about this. While I’ve been baking my own bread for almost a year and a half now, I’ve been using store bought flour. I know my bread is now preservative free, but what about the flour, the main ingredient.

When you grind it at home, you’re leaving in all the nutrition. It will store for one to two weeks, or you can store the ground flour in the freezer. Just be sure to remove the flour and use it before it turns six months old in the freezer.

When you grind a whole wheat berry (it looks like a piece of grain, not a berry), you are grinding the bran and germ into your flour. Because the germ has oil in it, the flour can turn rancid, so it’s removed in commercial flour. But most of your fiber, vitamins, minerals, and antioxidants are in the bran and germ.

The At-Home Process Explained

manual grain mill

Now to get down to business. Grinding wheat berries is no different from grinding coffee beans.  Easy as can be.  Pour your grain into the top of your grinder, called the hopper, set how fine or coarse you want your flour to be, put some ear muffs on, and turn it on.

That’s the grinding portion of the adventure. However, before you get to the grinding, you have to know what to grind. I found this a bit daunting when I did this the other day to prepare for this guide. Thankfully, once over the initial overwhelm, it is completely painless and straightforward.  

When it comes to wheat, there are basically five different options (not including durum wheat): hard winter red wheat, hard spring red wheat, soft winter red wheat, hard winter white wheat, and soft spring white wheat.

White wheat is not the same as what is colloquially known as white flour or all-purpose flour aka “devil flour” from the perspective of most diet books. White wheat berries are 100% whole grain. What is often referred to as white flour is not related to white wheat berries; they just happen to both be referred to as “white.” White flour, all-purpose flour or refined flour has had both the bran and the germ removed from the wheat berry.

Now, I ask you…why call them both white?  There isn’t enough confusion surrounding whole grains already?  Between the germ and the bran, and the fact that the hulled wheat is referred to as berries wasn’t confusing enough?  They had to add in this very confusing duplicated taxonomy? For the record: White whole grain flour is a real thing and it has nothing to do with all-purpose, processed flour.

I have to admit I was a bit slow on the uptake when it came to figuring out what wheat to buy for my first grinding endeavor.  I found myself googling “where do you buy whole grain grains?”  Then it dawned on me: if you are buying the WHOLE grain, it is therefore “whole grain.”

Embarrassing light bulb moment! I had been hearing “whole grain” as a type of flour, bread, etc… But I had not connected what the words actually meant. Whole grain means the WHOLE grain is ground to make the flour.  I know, really obvious, but hey, what can I say?

The best, and in my opinion only way to learn the taste/textural difference between all the different types of wheat is to bake with them. What is nutty to me might taste completely different to you. Don’t rely on another’s description, test it out for yourself.

How Did the Earliest American Flour Mills Work?

vintage old mill

Mills of early America were small, often one or two stories, but there was little need for tall structures (that came later with the Oliver Evans mill). Mills of this time period of early America contained the mill machine, consisting of the water wheel, gears and millstones. The millstones were often separated on a platform or a level separate from the first floor. 

The miller spent all of his time in the mill’s basement where he suffered from problems of cold, dampness, dirt, fungus, mold, mildew, and poor light. This is why the “miller’s thumb” was developed so the miller could judge the quality of the flour by using his hands and fingers without the benefit of much light to see by. 

The miller would only travel to the millstone level to fill the millstone hopper or dress the millstones. The millers or boys helpers did the rest. layers of old flour and meal covered the floors, corners, and cobwebs throughout the mill.

The grain gets to the millstone by being taken by a sack hoist to the top of the mill. When it is needed to be ground it then is poured through a chute down to the millstone hopper which dribbles it into the eye of the stone. The damsel is attached to the runner stone and spins around with it at about 125 r.p.m. The effect of this is to vibrate the shoe causing the corn to run down the slope. 

As the grain travels out from the center of the stone to the edge, it is ground up into meal. The meal collects in the wooden vat which surrounds the stones and falls through a small hole in the floor down a meal spout to the ground floor. Sometimes the miller would sift the flour or meal by hand using a hand sifter or the miller would collect the meal in a sack or tub and send it up to the top of the mill again on the sack hoist. 

After a time it would be poured down another chute into the boulting (later term bolting) machines which sieve the bran out of the meal, leaving the flour to fall into the flour bin. The bran or offals would be tossed out often by pouring it into the mill stream. A miller’s horse could always be easily identified because it would have rickets because it had too much bran in his diet.

Often the mill’s most complicated piece of machinery other than the millstones would be a windlass barrel hoist. A type of hoist that a rope is wound up around a barrel used to lift sacks, barrels, tubs on the inside of the mill (through trap doors) or on the outside of the front of the mill vertically up past a series of Dutch doors on each floor of the mills. 

Candles were used for lighting either sitting on barrels or on candle holders forged by the blacksmith with long spikes on the end that would either stick into barrel heads or beams.

One old expression is: “Don’t put out the miller’s eye.” The particular phrase has no reference to the eye of the miller. However people in Michigan have taken it to mean that only a good miller would have one eye, that he would keep his nose so close to the grindstone that he would poke out one eye in dressing the millstones. 

The original phrase has no reference to the eye of the miller, but probably to that part of the machinery of the mill known as the mill eye or eye of the millstones. If by the inattention of the miller, the grain flows too freely from the hopper through the shoe and fills the eye or the aperture of the revolving millstone and brings the machinery to a stand still. 

Another use is to “put out the miller’s eye,” in other words for the miller or one of his helpers to dump a large amount of grain to fill the mill’s eye and choke the millstones and machinery down to a sudden stop. To put out the miller’s eye with good whiskey (rather than grain) they would drown before they could ever put out the miller’s eye. 

The folks of Michigan have taken the old expression “keep your noise to the grindstone.” It means if you keep your noise literally always pointed towards the grindstone, your ears are also in that direction. The expression means pay attention to your work, by using your senses of sound, sight and touch to operate the mill.

The phrase “dusty miller” means the last child born in a family and should be really “dusty milder.” “It’s mildering” means that it is pouring rain. The Irish never say ‘pouring with rain.” Milder is a milling term that means the quantity of grain ground at any one time. So milder means a great amount, a flow, quantity, a deluge. 

The “melder, ” flour or meal fell into a great wooden tub, then the miller’s helper would have raised the tub to a flour bin or loft area. St. Mullins or anglicized to the name of St. Mulling. 

An Irish monk who lived from 614-696, and is remembered as having succeeded in milling (a mixture of non-grain stuff such as apples, nuts and other particles, fibers, perhaps belly button fuzz, etc.) into rye flour after a disastrous harvest. He is the famous miller who may be the source word for “Molinology.” 

His mill race and remains of his mill can still be seen. He is supposed to be the earliest person who was named a “miller.” So is the study of milling meaning “Molinology ” comes from the study of St. Mulling. The Dutch word for milling is “molin.”

Dutch and German mills constructed in America tend to use German millstones. These millstones are quarried at Nieder Menting in the Mayen district of the Rhineland, and were used by the Romans who went through a great deal of effort to haul stones to their mills from the Rhine River. The stones are known as “Cullin” stones, a corruption of Koln, the German name for the city called Cologne in English. 

The millstones are made of a bluish-gray lava and they tend to use a sickle millstone dress pattern on the grinding surface. The English settlers in the New World favored millstones from their motherland. So English mills and millers use stones cut from quarries in the Peak District of southwest Yorkshire and the northeastern perimeter of Derbyshire. 

This millstone material is known as Millstone Grit. The British millers refer to these millstones as “Peak” or “Gray” stones. Grist mills constructed by the English more than likely had a pair of English millstones and looked much like a traditional English Country mill.

I highly recommend this insightful video for more about the origins of commercial flour mills: