Daf Yomi - Moed Katan 10 - All About Millstones

The Mishna states: One may set up an oven or a stove or a millstone during Chol Hamoed. Rabbi Yehudah says: One may not groove a new millstone.

The Gemora explains the prohibition against grooving. Rav Yehudah says: It is referring to cutting grooves in the millstone (if the millstones are smooth, they will not grind the kernels properly – cutting grooves accomplishes that the surface will become rough). Rav Yechiel says: It is referring to cutting the eye-hole (the hole in the upper millstone through which the kernels enter).

Rabbi Yoseph Dov Karr did some terrific research on millstones - please scroll down (after the blank space, which I can't get rid of) and click the "read more" link and see. Yasherkoach Gadol!!!!!!!!!!
http://www.angelfire.com/journal/millrestoration/millstones.html

The Movement of the Millstones (Starting and stopping a pair of millstone)
The miller would open a sack of grain and pour it into the millstone hopper, or the grain would already be stored above the millstones in a bin on the floor above. The miller would simply reach over and open a gate that would fill the hopper with about 50 to 100 pounds depending upon the type of grain.

Now the miller was ready to start the mill. Then he must open the control gate on the mill's sluice box. There are several schools of thought about starting and stopping a mill. One is that the millstones should be together, the miller opens the control gate and the water begins filling the upper buckets of the water wheel. As the water fills the first bucket it over spills into the second and then third and so on. When the water is over flowing the water wheel the miller will slowly begin to raise the runner millstone. The water wheel would begin to turn as well as the gears and the millstones. The machinery in the mill would come alive and very quickly the mill will begin to turn at a fast speed. All the time the grain has been slowly fed into the millstones and the miller now lowers the runner stone closer to the stationary bed stone, and the material coming out from the millstones grows finer and finer. Then gradually the miller adjust the millstones for the desired grind.

The other method is the opposite, before turning on the water onto the wheel, the miller raises the top runner millstone as far as its adjustment will allow it to rise. Then the miller goes and gradually begins to open the control gate, and the water then begins to slowly fill the first bucket on top of the water wheel. When the water has filled the buckets so that the top of the water wheel is heavier than the rest of the wheel, the water wheel will begin to turn. As the water wheel begins to turn and gain in speed the miller then begins to slowly lower the upper runner stone downward and the material begins coming out of the millstones becomes finer. Then the miller adjust the millstones for the desired grind that he wants.

One method is about as good as long as it is not hard the machinery. There is also several different ways you can stop the mill. One method of stopping the mill is just to close the control gate, and when the water stops flowing the mill will stop. A variation on this method of stopping the mill is to close the control gate and when the machinery begins to slow down you gradually raise the runner millstone. When the weight of the water wheel equalizes or when the water empties from all of the buckets the machinery will stop. Both methods will work for gear and belt driven pairs of millstones. The problem is the lag time it takes once you close the control gate to when the machinery actually stops. This can be a very long time of part of the mill's machinery is broken or jammed, or especially if someone is caught in the turning parts of the mill.

Another method of stopping the millstones is to push an extra handful of grain into the millstones. The millstones with the added amount of grain will act like a car that has sudden gotten too much gasoline, it will be begin to stall. When this happens you gradually bring the two millstones together with the added cushion of grain between the millstones. The added weight of each millstone together should over take the weight of water and the mill suddenly stops as if you applied the breaks. This is a good method is something breaks or someone or something gets caught in the machinery. In a mill where the millstones are belt driven the drive belt turning the millstones may suddenly jump off or snap so this method works better with gear driven millstones. The problem is with the old style of wooden mill gearing is when the gear teeth are worn too much they may suddenly snap like match sticks but if someone is caught in the machinery you take that risk. A new problem or danger may arise when you have forgotten that the water wheel still contains kinetic energy or water enough to make the wheel turn wildly until it empties. What then may happen is if you forget about the water in the wheel and begin raising the runner millstone to clean between them after a days work using the millstone crane. The millstone will whip off the millstone spindle wildly when raised by the millstone crane. It will quickly screw itself off of the millstone spindle and stop once it has cleared the spindle. The millstone still may come loose from the bails and pins dropping through the floor going downward into the mill's basement.

Many a miller may still use this method of starting and stopping the mill by gradually bringing the millstones together because he never has to close the control gate just raise and lower the runner millstone, and to then adjust the grind. Water will then fall over the stopped will and create an interesting effect for people passing by the mill. Some people passing by the mill may then be drawing into the mill by unusual effect of water cascading over the wheel.

The Action of the Millstones (A pair of millstones for producing fine flour)

Most people do not know the exact process at work underneath the millstone cover. All they may see is the millstone hopper which is an open upside down pyramid sitting on top of the millstone cover full of grain. Some millstone hoppers have a control gate to regulate the flow or the volume of grain moving out of the millstone hopper through the bottom approximate 4 by 4 inch hole or opening. If the millstone hopper has a gate to control the flow, it may just be a small wooden paddle, a single arm mounted in several straps also made of wood. The gate slides up or downward. Usually once it is adjusted the miller never has to touch it unless he wants to change the rate of the grinding or change the type of grain he is grinding on the same millstone.

The grain then falls into a device hung below the hopper with leather straps called a shoe. It is called a shoe because originally it looked like a wooden shoe but slowly over the years its design has changed. The shoe can be raised or lower at one end to allow more or less grain to fall into the millstones. To ensure that it is always a constant rate the shoe is vibrated back and forth a turning damsel. The damsel is mounted on the top of the balance rynd in pockets in the center hole of the upper turning millstone. The top end of the damsel is turning in a hole in the wooden horse frame that holds the shoe and millstone hopper. Some damsels are adjustable up or down a metal shaft so they can be used on different millstones. Some damsels are metal shafts with wooden blocks or strips screwed to the shaft while others are made of wood with large round wire staples placed around the shaft to create raised or fluted ridges. Some millers may have different damsels for different rates of feed. One damsel may have only 4 flutes while another may have 6 to a dozen fluted edges around the shaft.




Drawing "Millstone" by T.R. Hazen, 1984.
The damsel got it same back in the days of Chaucer's Canterbury Tales when some make chauvinist miller referred to the rapping sound the shoe made against the turning shaft as like a damsel singing her song. The mill was never silent as long as she would be singing her song. The damsel would be constantly singing her song and make the make work.

The ensure that the shoe always makes contact with the damsel some mills have a wooden spring or "miller willow," attached to the side of the horse frame on the side opposite of the long arm that wraps around one side of the damsel. A millers willow is a wooden spring made out of ash wood and a string is attached around a notch in the end of the spring to the end of the shoe, usually through the same hole that the crook string is looped.

The grain falls into the eye of the runner stone, and the flow of grain is controlled by the arrangement of the shoe and the damsel rather than by the size of the hole or "eye" of the stone. With the turning runner the balance rynd and below that the driver spread the grain evenly between the two stones as it falls and hits these two turning bars. The gap between the two stones is regulated by the miller to adjust the fineness of the flour. These working surfaces of the millstones is hidden from view when the mill is operating to create a down draft that cause the ground material to be carried down a chute. Most people only see the grain going in and where the flour comes out a chute, and what is in between it remains a mystery.


A bed stone and its runner stone
Around the edges of the millstones and to the inside of the millstone cover normally lays 20 to 25 pounds of ground material and the excess falls down the chute. Traditionally the miller would only lift the millstone cover to clean between the millstones. At that time it was usually tossed out or used for animal feed. A dishonest miller might lift the millstone cover after each batch of grain he ground taking that amount as an excess toll. Sometimes the millstone cover was much larger than the size of the millstones so the miller could take more or possibly instead of being round it had multiple corners to trap an excess amount. This was called the "miller's mite" the stuff that fell though the cracks or was trapped in the system belonged to the miller.

In ancient mills the millstones turned in a round trough with a chute on one side but as time passed mills began to have more power so the millstones gradually became more covered to keep down the dust. The millers though that they needed small paddles of sweeps attached to the rim of the turning stone to keep the ground material at all times going down the chute. The added weight of these small paddles effected the balance of the millstone or got caught against the inside cover. Then in time the millers discovered they were not needed. Because air is drawn into the stones with the grain to keep them cool at long as the cover is over the millstones there is a down draft that is created that carries the grain down the chute beyond the amount that lays around the millstones.

A drawing from one of the HABS-HAER sheets


Most people have never been in a mill when it is operating let alone know what happens between the two millstones. Often people refer to the millstones as rocks and as far as they know the rocks mash up the grain up into flour. Many years ago the people who advocated using the modern roller milled flour began an old wives tale that says, "You don't want to eat stone ground flour because you might bite down on a piece of rock from the millstone." That is just not the case you don't get any stone particles in the flour normally when the mill is grinding because the millstones never touch. A pair of millstones need to be redressed every three or four week and in that time a pair of millstones can grind two to three hundred thousand pounds of grain.

There is a rare case that one may find stone chips in the flour but it does not come from the grinding action of the millstones but from the neglect of the miller or millstone dresser. After a pair of millstones have been dressed, no matter how well they have been swept or vacuumed they still contain small particles of stone. They need to be purged of the stone chips so that when you grind for the public the product is stone free of these chips. The amount of grain that you need to grind between the millstones to purge them after dressing is about one sack of grain (50 to 75 pounds). The miller may use an old sack of old grain that he would have tossed out normally. Once the grain is run through the millstones it should always be thrown out. The miller also uses this grain to see if the millstones have also been dressed properly. Sometimes he may have to take them apart again and do some more dressing.

The reason that the millstones should never touch are for the following reasons: (1) The stone of the millstone would be reduced into the flour or meal. (2) The millstones would wear out very quickly. (3) If the millstone actually touch they may stop or (4) most importantly they would create a shower of sparks. The dust from wheat, rye, barley and oats is more explosive than gunpowder and 35 time more explosive than coal dust. Corn and buckwheat do not contain explosive dust because corn is a different cereal grain and buckwheat is an herb. Buckwheat and rye produce the most dust of them all in the process of grinding. (5) Finally if they touch they would tend to stop.

Technically the millstones will do some grinding of the grain without anything on the grinding surface. Some say that porous opening in the French millstones are enough to create the grinding action between two millstones without dress. And then, of course, the rest is left up to the art of the miller how he maintains his mill and the millstones. The miller may or may not be forth coming with information about what happens between the millstones. Some millers will only goes as far as the grain gets ground up between the two rocks. This response that it is stone ground, may be your only answer in some cases. The good miller who knows that the millstones should have sharp surfaces furrows to provide more efficient grinding of the grain.
Furrows and Lands (The grinding surface of the millstones)

A pair of millstones lies hidden from view in a wooden case called a vat. The millstones work together in pairs with a revolving upper turning millstone called the "runner" stone, and the fixed stationary bottom stone called the "bed" stone. Many people have lived their whole lives taking sacks or turns of grain to the local mill to have it ground into flour or meal and have never seen the millstones apart to see their surface or the process of maintaining the grooves which is called "dressing."

A discarded millstone outside and removed from the mill may or not be laying on its back to reveal patterns of furrows and lands on the grinding surface. So that is this pattern of the "grinding beams" beams used for in the milling process some may ask.

Are they used for cutting the grain into flour and meal? Or are they used as "furrows" in the farmers field to move the farmers plow across the "land," but in this case it moves the grain across the land of the millstones. They could be "air-furrows" for the movement of air between the two millstones to keep the grain from over heating? Then they could be "pairs of furrows" used to transport the grain between each pair of crossing furrows create a cutting against each other like scissors.
Cutaway Drawing of Millstones in Use.
This cutaway shows the grinding action of two millstones with a right hand dress.
The furrows are used to cut the grain like a pair of scissors, as well as move the grain outward from the center of the millstones to the outer circumference and they are used to increase the air space between the millstone to keep the grind cooler. The condition of the pattern makes up for the "sharpness" of the millstones and for the fineness of the flour. A "dull" pair of millstones will not properly grind and separate the brain from the inner kernel and take more power to operate. A dull pair of millstones will not scrape off the bran in a large flake but with tare it into small particles which is then difficult to sift out from the flour. So a sharp pair of millstones will scrape off the bran in a nice large flake and then continue to reduce the inside endosperm into smaller particles.

The furrows do not radiate outwards from the center of the stone like many would think. Rather they are more or less set at a tangent to the eye of the stone. They are arranged in groups known as harps or quarters, each group consists of a "master furrow" which runs from the eye of the stone to the outer edge. The master furrow is the primary furrow on the surface of the millstone. There is a variable number of secondary furrows, perhaps three or four or five furrows. The first secondary furrow is called the "journeyman furrow," this is the second largest furrow in a quarter of a millstone with quarter dress pattern, parallel and immediately adjacent to the master furrow on one side and the next furrow or apprentice furrow on the other side. The "apprentice furrow" the third largest furrow in a quarter of a millstone with a quarter dress pattern, parallel and immediately adjacent to the journeyman furrow on one side and the butterfly furrow on the other side. "The "butterfly furrow," the smallest of the four millstone furrows in one quarter of a millstone in quarter dress. Sometimes this furrow is also called the fly furrow. If the millstone has a fifth furrow it may or may not have a name depending upon if the miller or millstone dresser gives it a pet name or not.

What happens when the grain falls into the eye of the millstones, it is moved outward between the two millstones by the turning motion of the upper runner millstone. The one method to discover what happens when the stone is grinding is to take the millstones apart after they have been doing some grinding of grain. As you look between the two millstones across the bottom millstone surface you will discover that the grain is in different phases of being reduced into flour or meal.

So beginning at the center or eye of the millstones where the grain is introduced between the two millstones you would find whole kernels of grain. A kernel of grain encounters large deep furrows that move it outward between the millstones. In this beginning process each kernel of grain would encounter 10 pairs of master furrows crossing each other and thus chopping the grain into small or broken bits of grain. In other works it makes cracked grains in the center of the millstones. If this were a roller milling process this would be the first break roller step.

At the grain spirals outward it will encounter a the second pair of additional furrows called the journeyman furrows and the grain will then become cut 20 times in this phase or like a second break roller step. The one difference beside twice as many furrows in this point of the millstone surface is that depth of the furrows is shallower than they it was at the millstone eye because the particle size is also getting smaller.


A standard text book (apprears to be English) illustration of a millstone.
The caption reads, "Common dress for a 4 ft. diameter millstone."
The old time millers who spoke about how many "quarters" a millstone had and how may furrows were in a quarter, it was also customary to speak about the millstone surface into three divisions. In the center was the "eye" or "bosom," in the middle is the "waist," and at the outer it is known as the "skirt." The bosom and waist is kept down more or less hidden below and behind the skirt so they cannot be seen.

The furrows at the leading edge of the eye are usually from one quarter to three quarters of an inch in depth, and this depth gradually is tapered off to come up to the surface of the stone at the skirt. The width of the furrows of a millstone are usually between one inch and one and a quarter inches in width.


Scissors cutting action of a pair of millstones as seen from the end view of two furrows.


The grinding surface of the millstones are divided between "furrows" and the "land." The furrows are grooves or channels cut out or into the face of the millstone. The furrows are deeper at the eye and become shallower as they move towards the skirt. Looking at a furrow from the side it has two separate edges. The "back edge" or bottom of the furrow is a sharp incline plane downward from the surface of the land. It culminates in what is known as a "front edge" or "feather edge." The feather edge tapers upward to meet the land, and it is the cutting edge of the furrow. The parts of a furrow are the back edge, heel, the bottom, and the feather edge. The lands are the portion of the face of the millstone left between the furrows and are in reality the true grinding surface of the millstones. This is because the grain is moved below the surface and when it returns it meets two surfaces or lands and it is sheared at this point by a constriction. The furrows purpose is then for distribution, ventilation and cutting because the grain is cut near where the feather edge meets the land.



Scissors action of a pair of millstones.
As the upper millstone moves across the surface of the lower millstone the large kernels of grain are trapped in side of the two back edges but as the millstone rotates a the grain is carried up the slop or incline where it meets the land or surface of the millstone. The sharp leading edges of the lands, passing over corresponding edges in the other stone, act rather like the blades in a pair of scissors, shearing or cutting the grains into fragments. The crossing feather edges constrict the grain within a smaller space and a shearing action occurs. If you take apart a pair of scissors a single blade is the same basic shape as a single furrow.

If the furrows did not answer their purpose of distribution, ventilation and cutting or breaking and there was no furrows on the millstone surface then the grain might be crushed. The problem with crushing the grain or applying too much pressure upon the grain as it is being ground is it that the oil is released from the germ in to the flour and will quickly cause it to turn rancid. As the grain is passed through the millstones it passes outward in two and one half revolutions. So as it is cut into four or five pieces and would continue to discharge it in a normal manor when every thing is fine and correct. But if it is tends to move outwards and be crowed and clog, then the draft is too severe. If it discharges too quickly with out being properly being ground, then the draft is too shallow. If the crowding occurred in the eye or the bosom of the stone then the grain will tend to lift the runner stone over coming the weight and pressure of the millstones and create great friction resistance, building up heat and moisture in the passing of the grain through the stone. The angle of the furrows is such that as they sweep across each other the grain and flour is forced outwards towards the edge of the stones. A rare type of millstone dress occurs when the furrow reached the outer last 6 to 8 to 10 inches of the millstone it will suddenly change direction and thus give the material a rapid movement outward which tends to distribute and discharge the material after reaching this point. This type of millstone dress is found in the 1764 Stillwater Mill in middle of the village of Stillwater, New Jersey.

When the millstones are normally grinding the weight of the turning upper millstone is transferred to the grinding action. So none of the weight of the stone is upon the bottom millstone spindle bearing. This is one reason that the millstone never should run empty it that the weight of the upper turning stone would quickly destroy that bearing.

When the material reaches this portion of the millstone the last 6 to 8 to 10 inches of the millstone they become vary close together. If you take a pair of millstones apart and lay a straight edge across the eye of the stone from one skirt to another. The millstones are not flat but each stone has a slight dishing to the surface. This is so as the grain moves outward in its two and one half revolutions the the particle size becomes smaller and the millstones become closer together. So as they reach the outer edge they may be only a paper thickness apart This area is called "the flouring of the stone" is the outer section of the grinding surface of the millstones where they come close together and the actual grain is turned into flour. Here the cracking lines are located and the are more furrows reducing the grain into flour. The flouring of the stone is like the reduction rollers and the cracking is like the germ rollers in a roller system.

The flat surfaces of the lands, which are roughened with small parallel grooves called stitching or cracking, they also pass across each other, grinding the fragments into still finer flour. In the process of dressing a millstone it is done in several steps. Facing is done to the surface painted on the lands, dressing is done to the furrows and cracking is done to the lands. The process is called "cracking" which means the laying in of "cracks" and leaving a space between the cracks. A cracking lines is just made with the sharp point or cutting edge of the mill bill. So if you looked at them closely from the side they would be V-shaped. The cracks extend across the land of the flouring of the stones and are varied in fineness as the occasion requires. A skillful stone dresser could put in 10 to 12 or perhaps 20 to 35, or even 50 cracks per inch with a full width of the pick or bill. The cracks are a series of parallel lines land across the land between the furrows. Some millers or millstone dressers see the need for cracking in a millstone while other say that it makes no difference. Usually millstones used for corn have no cracking and it is only found on millstones used to grind wheat and producing white flour.