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Mill Terminology


Windmills may be based upon simple physics, but they are truly complicated machines.  Understandably, there are a number of terms and parts associated with windmills, and a few phrases that we now use in everyday conversation actually originated from milling.  


Air trunk (custom)

A passageway to the exterior of the mill, usually for blowing out trash particles from clean grain (present only on mills with smutters).


Anchor [Post] or Bollard (custom)

A metal or concrete block in which a chain or rope is looped around the neck of the anchor and, when taught, pulls the tail pole to luff the cap.  May also be used to tie down the sails when not in use.  These are found in ground-sailing mills or beltmolens, like De Immigrant.  

Anchor bolt (all)

1. A large, iron or steel eyebolt in which a chain or rope is threaded through the eye and, when taught, pulls the tail pole to luff the cap.  May also be used to tie down the sails when not in use.  These are found on tower-stage mills, like the Fischer Windmill.

2. Name for a bolt embedded in a foundation (usually of stone or concrete) used to fasten a structure (such as an engine or turbine tower) to it.


Anchor iron (custom)

An iron strap that secures the brake band to the cap structure.


Angle of weather (all)

The twist in the sails of a windmill, designed in such a way that the wind will cause the sails to turn in a certain direction.


Annular sails (all)

A series of thin, paddle-like sails fixed to a wheel of relative diameter.


Backing (custom)

The smooth face of a grinding stone, opposite to the grooved (dressed) side.


Bail Holes (custom)

Holes cut into the sides of grinding stones so that bails may be inserted.


Bails (custom)

A crane-like structure with iron tongs used to lift the mill stones.  Once fastened, a miller can turn the stone by hand to raise it along a threaded stud, then swing it out of position to perform maintenance.


Balance box (custom)

Name given to the holes on a runner stone that hold weights to perfectly balance the stone’s rotation.


Band brake (all)

The type of brake used to stop the turning of the sails.  When activated, friction blocks clamp the sides of the brake wheel, thus slowing the rotation of the wind shaft.


Beard (custom)

An ornamental wooden piece fixed to the front of the cap below the wind shaft indicating the year of construction (usually present on Dutch-built windmills only).


Beater (custom)

A metal piece inside a scourer that is designed to clean wheat by whipping wheat berries against the side of the scourer to centrifugally remove chaff, dirt, and other debris.


Bed stone (custom)

The lower grinding stone, which remains motionless.


Belt (custom)

Name given to the grain elevators within the windmill.



See Sails


Bolting machine (custom)

A machine that separates ground wheat products by passing them through a series of sieves for proper bagging and shipping.


Brake band (custom)

The metal band that squeezes friction blocks against the brake wheel.


Brake lever (custom)

An external lever located in the back of the cap used to active the brake.


Brake post (custom)

A hinge built inside the cap that connects the brake lever to the braking mechanisms.


Brake rope (custom)

The rope or chain that runs from the brake lever to the stage so that the miller may engage or disengage the internal brake


Brake shoe (all)

Term to describe the friction blocks that comprise a full brake.  On custom windmills, these are made of wood; on engines and turbines, usually metal.


Brake wheel (all)

A cogged wheel located on the wind shaft of any windmill.  Because the brake surrounds it, this wheel has the power to stop the windmill’s movement.


Bridge (custom)

A specially shaped metal piece located in the eye of the runner stone used to couple it to the quant


Canister (custom)

The head of a metal wind shaft where the sail stocks are bound, or a metal piece that aids to clamp the four timbers of a wooden wind shaft together.


Cant post (custom)

The name given to the main beams located at the corners of a wooden windmill tower (i.e., the eight main beams at each corner of an octagonal tower)


Canvas sails (custom)

See Common sails


Cap (custom)

The top floor of the windmill; it houses the wind shaft, brake, brake wheel, and brake lever.  The cap is able to rotate upon the tower thus allowing the sails to face into the wind no matter which direction it blows from.


Cap frame (custom)

The basic framework of the cap, specially designed so that it may rotate upon the tower and so that it can hold and balance the machinery.


Case boards (custom)

The wooden boards that enclose the grain elevator shaft.


Centering frame (custom)

The frame built at the top of the tower that holds the curb ring in place and balances the cap.


Chaff (custom)

Unnecessary wheat berry debris.


Check valve (engine)

A valve that opens and closes based on water pressure to fill the pump chamber of a wind engine


Cloth sails (custom)

See Common sails


Cog [wheel] (all)

A driving wheel with teeth designed to drive other cogged wheels.


Collar (all)

The name given to the bearing attached to the front end of the wind shaft to keep it from wearing (located, ideally, on the “neck” of the wind shaft).


Common sails (custom)

Traditional lattice-structure sails requiring the miller to reef canvas (like on a sailing ship) to catch the wind.


Conveyor box (custom)

The wooden sides that contain the spiral conveyor.


Cracks (custom)

Grooves that are etched into the grinding stones.


Crane holes (custom)

See Bail holes


Crotch spindle (custom)

See Quant


Crown wheel (custom)

A wheel located on the upright shaft that drives the movement of grain elevators or a sack hoist.


Curb ring (custom)

The wooden ring atop the tower upon which the cap rotates.


Damsel (custom)

A device the taps the feed shoe so that grain will pour into the eye of the runner stone.


Date Board (custom)

See Beard


Dead curb (custom)

The name given to a greased wooden curb ring on which the cap rotates (as opposed to a Live curb)


Diagonal braces (custom)

Long pieces of timber that connect the front and rear ends of the cap to the tail pole so that the winch may rotate the cap.  This allows the weight of the cap to be evenly distributed without putting too much pressure on the tail pole alone.


Dress (custom)

[noun] The pattern of furrows or cracks etched into the grinding stones.

[verb] The act of etching furrows into the face of a grinding stone.


Dump bin (custom)

A hopper into which grains are poured upon delivery by the farmer (especially in mills with grain elevators).


Dust collector (custom)

Part of a separator machine where dust particles are gathered before they are expelled.


Dust floor (custom)

The floor in the tower immediately below the cap.


Eye (custom)

The center of a grinding stone


Eye [of the wind] (all)

The direction from which the wind is blowing


Face (custom)

The grooved side of a grinding stone.


Feed shoe (custom)

Allows grain to travel from the hopper into the grinding stones.


Flake (custom)

A verb meaning to disassemble and relocate a mill.  A common practice with the landowners of wooden mills in Europe.


Flight (custom)

The name given to a wooden paddle in a spiral conveyor.


Fly-ball governor (custom)

A metal device used in part to automatically tenter the stones based on wind speed.


Friction block (all)

One of several blocks that comprise one of the brake shoes, grooved (or unfinished) to provide stopping power to the brake.


Furrows (custom)

Flat channels cut into grinding stones.


Garner (custom)

Another name for a grain bin.


Gearbox (engine)

Part of a wind engine that houses the gears, pump rod, and oil reservoir.


Generator (turbine)

Part of a wind turbine that produces electricity from the rotation of the wind shaft.


Gorging (custom)

The term given when uneven amounts of grain are present in both runs of stone (this can be dangerous, as it may cause more friction in one set of stones than in another, which in turn adds pressure to the drive train).


Grain elevator (custom)

A belt fitted with cups enclosed within a wooden casing that sends prepped grain from the main floor to the upper floors of the mill, where it is dumped into hoppers for grinding.


Grain elevator legs (custom)

The inclined elevator shaft that usually runs from the first floor to the floor above the grinding stones.


Great spur wheel (custom)

The main cogged wheel in a windmill that directly drives the two (or more) quants for the grinding stones.


Grinding floor (custom)

See Stone floor


Grist (custom)

Prepared but yet-to-be-ground corn.


Half-bearing (all)

A block of stone (or metal) upon which the neck of the wind shaft rests and is balanced.


Heel (all)

The part of the sail closest to the wind shaft.


Hemlath (custom)

A wooden strip that runs most of the length of the sail’s outer edge.


Hopper (custom)

A storage unit that funnels grain into the grinding stones.


Horse (custom)

A frame that holds the hopper onto the vat.


Hub (turbine)

The “nose” of a wind turbine that holds the three sails in place


Lands (custom)

Flat surfaces between furrows on the face of a grinding stone.


Lighter staff (custom)

A lever located on the ceiling under the grinding stones used for tentering.


Live curb (all)

An iron or wooden curb ring that uses wheels or bearings to ease cap rotation (especially on mills with tail fans, or on mills where the winch is located within the cap rather than on the external tail pole).


Luffing (all)

The process of rotating the windmill so that the sails can face into the wind.  This work can be done by: hand (post mills); by winch or capstan wheel (smock mills); by tail fan (tower mills); by vane (wind engines); or by computer controls (turbines).


Meal floor (custom)

The floor in the tower where the product is bagged (almost always the floor directly beneath the stones).


Nacelle (turbine)

Name given to the top, pivoting section of a wind turbine (same as the cap of a custom windmill or the gearbox of a wind engine)


Neck (all)

The end of the wind shaft closer to the sails.


Outside winder (custom)

A windmill whose cap is turned externally by a tail pole.


Overdrift (custom)

The term given to grinding stones in which the runner stone is on top.


Patent sails (custom)

See Shutter sails


Pump rod (engine)

A long rod driven by the gearbox of the wind engine to pump water from an underground well.


Quant (custom)

(or Crotch spindle) runs from the stone-nut to the bridge in the runner stone.


Quartering (all)

The act of turning the cap ninety degrees against the direction of the wind during a severe storm to prevent wind damage to the sails (and to prevent extreme winds from turning the sails).


Runner stone (custom)

The stone that is turned by the quant.


Run of stone (custom)

A term referring to the number of complete stone sets a windmill has (usually two or three pair).


Sack hoist (custom)

Uses wind power (driven by a crown or friction wheel) to lift sacks of grain to the upper floors (as opposed to windmills with grain elevators).


Sail (all)

What all mills use to harness the wind and/or to support a canvas cloth also used to harness the wind.


Sail bar (custom)

A short wooden strip that is attached to the whip.


Sail stock (custom)

A heavy piece of timber that binds two whips to the wind shaft.


Saint Andrew’s cross (custom)

Leaving the sails locked in an “X” position, expressing that the miller is taking a long rest.


Saint George’s cross (custom)

Leaving the sails locked in a “+” position, expressing that the miller is taking a short rest.


Scourer (custom)

A machine used to separate usable grain from debris such as dirt, dust, and chaff.


Separator (custom)

A machine used to separate grain from other foreign objects, such as rocks, weeds, and sticks.


Sheer-tree (custom)

The name given to two beams that rest and balance the cap on the curb ring.


Sheller (custom)

A machine used to separate kernels of corn from the cob.


Shutter sails (custom)

Sails consisting of a series of shutters akin to blinds in a window that operate by opening or closing to allow or restrict air flow.


Sieve (custom)

A screen used to filter the finished product based on granularity.


Skirt (custom)

The bottom edge of a wooden Dutch tower mill, designed to protect the foundation beams from weathering, giving the name “smock mill”.


Smutter (custom)

A combination machine that acts as a Separator and a Scourer.


Spiral conveyor (custom)

Used to transport the finished product by means of wooden paddles arranged in a spiral.


Stage (custom)

The platform surrounding the tower from which the miller operates the windmill by winding the cap and releasing the brake to allow the sails to turn.


Stone floor (custom)

The floor of the tower where grain is ground.


Stone-nut (custom)

A wooden gear that engages the great spur wheel to turn the quants.


Stone spindle (custom)

The bearing the runner stone rotates upon.


Storm hatch (custom)

An opening in the cap, either at the front or the rear near the wind shaft, that allows the miller to access the cap and sails for repairs.


Sword iron (custom)

An iron strap that connects the brake lever to the brake itself.


Tail beam (custom)

A beam within the cap that supports the tail pole.


Tail-bearing beam (custom)

A beam within the cap for the bearing of the poll end of the wind shaft.


Tail fan (all)

A small set of sails, usually located behind the cap (or gearbox, or nacelle) that runs perpendicular to the main sails. When the wind blows from a different direction, the tail fan drives a gear to swing the main sails into the new direction of the wind.


Tail pole (custom)

A large piece of timber that runs the length of the tower from the cap to the stage.  It also supports the diagonal braces and has a winch or capstan wheel attached to it, all necessary for winding.


Tail wind (all)

Winds that blow in a direction completely opposite to the way the sails are facing.  This can cause severe damage to the mill.


Tentering (custom)

The process of controlling the distance between the grinding stones.


Tip (all)

The part of the sail furthest from the wind shaft.


Toll spout (custom)

A chute used to collect the “toll”, the miller’s payment.


Tower (all)

The tall, bottom portion of any windmill


Underdrift (custom)

The term given to grinding stones in which the runner stone is on the



Uplong (custom)

A wooden strip that runs most of the length of the sail.


Upright shaft (custom)

The drive shaft that runs from the wallower to the great spur wheel and may also drive the crown wheel (or friction wheel).


Valley (custom)

The lower part of a hopper, named for its shape.


Vane (engine)

Name given to the tail of a wind engine, which keeps the annular sails faced into the eye of the wind.


Vat (custom)

A wooden drum that surrounds the grinding stones.


Wallower (custom)

A wooden nut that is driven by the brake wheel and delivers power to the main upright shaft.


Whip (custom)

The long piece of timber that contains the sail bars, uplongs, and hemlath of the sails.


Winch (custom)

A device located on the tail pole near the stage so that the miller can rotate the cap.  Turning the winch reels in a chain, secured by two anchor bolts, thus pivoting the cap upon its curb ring.


Wind board (custom)

Leading edge of the sail which may be covered by wooden boards to help the sails catch the wind.


Wind farm (turbine)

An area of land (or water) containing many wind turbines, usually supplying power to a single plant.


Wind shaft (all)

A long, inclined shaft that rotates the sails and holds them together.  Can be made of metal or from four large pieces of timber clamped together.


Wind wheel (all)

See Annular sails


Winding (all)

See Luffing


Yaw control (turbine)

An electric motor that turns the hub of a wind turbine into the wind (similar to the tail-fan in the cap of a custom windmill)


Yoke (custom)

On early post and tower mills, a wooden device built into the tail pole to support the shoulder of the miller as he turned the cap.



Milling-related Phrases


First come, first served

This was the law for millers in many countries.  Because it could take days for a farmer to have his grist ground, the law was designed to prevent impatient customers (or those receiving special treatment from the miller) from jumping ahead in line.


Wait [for] your turn

When referring to the rotation of a windmill’s sails, “turn” (not “spin”) is the correct term.  Farmers had to wait in line—sometimes for days—until the windmill would “turn” to grind his grain.


Grist for one’s mill

Since wheat and corn are ground by “teeth,” the grinding stones “chew” the grist into flour; thus to “chew” over something was applied to the act of thinking or pondering an issue.


The daily grind

This phrase had the same application then as it does now, only the job literally involved grinding.


Keep your nose to the grindstone

Millers had to keep to the stones to smell for flour burning; if the stones created too much friction from grinding close together, the flour could ignite (and, because most windmills are made of wood, could burn to the ground in a matter of minutes).


Come to a grinding halt

A sudden loss in wind power (and thus a loss in momentum) could cause the runner stone to drop and grind against the bed stone, causing the mill to suddenly stop (and cause a great screeching, grinding noise in the process).  The phrase now seems to apply to bad brakes on a car, or anything that stops both suddenly and awkwardly.


Rule of thumb

A miller could determine the fineness of the flour or cornmeal by rubbing it between his thumb and forefinger.  If the product was still to coarse, he may mill it again.


Put your shoulder to the wheel

Refers to winding a small post mill, in which the miller must put his weight into moving the tail pole (which has a wheel at its poll end) and pivoting the mill into the eye of the wind.


Three sheets [to the wind]

A [four-sailed] windmill with only three of its sails covered in “sheets” of canvas will turn clumsily because it is off balance.  Thus, the term is applied to drunks.


Tilting at windmills

Many people mistake the term for simply looking up at windmills, but the term “tilting” refers to the act of charging one’s lance at his opponent in jousting, as was the case in Cervantes’ Don Quixote.  Tilting at windmills, based on the story, means to battle an invisible or imagined enemy.



Milling Phrases
Annular Sails
Common Sails
Shutter Sails
Stone Floor
Wind shaft
Tail pole
Tail wind
Brake band
Runner Stone
Brake wheel
Grain elevator
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