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Don't know your spur wheel from your stone nut? This glossary explains the meaning of some of the windmill terms you will see.

Bed stone The bottom millstone, which doesn’t move

Bin Container for grain on the bin floor

Brake Lever-operated device working on a rim of the brake wheel to prevent the sails from turning

Brake wheel The first gearwheel in the power train. Attached to the windshaft, it drives the wallower. The brake, usually a ring of wood, grips the outside of this gearwheel to slow the mill

Cap Wooden structure that turns at the top of the tower and contains the brake

Common sail Earliest and most powerful type of sail. A sheet of cloth pulled, like a curtain, over a wooden frame. The same idea as sails on a ship.

Curb Metal rim that supports the cap on top of the tower. It is fitted with rollers so that the cap can turn more easily on the metal plates

Centring wheels Metal wheels that keep the cap centrally within the curb

Canister An iron device consisting of two open-ended boxes at right angles to each other, through which the main sail timbers are fastened and joined to the windshaft. Also called a poll end

Eye The central hole in the runner stone where the grain enters

French burrstone The best type of stone for grinding wheat, used throughout Europe.  Relatively expensive small segments of stone are set into plaster of Paris

Governors A set of spinning balls that use centrifugal force to act on levers to keep the gap between the grinding stones constant as the wind changes speed

Grist The name for any grain that is fed into the stones. It’s all grist to the mill

Hopper A large (usually) wooden funnel that stores the grain and then feeds it down into the stones

Meal The name for any grain that has been ground by the stones

Millstone grit Also known as peak, grey or gritsone, usually from the Derbyshire Peak District

Patent/Spring sails

Spring sails have shutters with a spring to enable each sail to be adjusted individually. The Patent sail system allows all sails to be adjusted without stopping the mill. Most popular design patented by William Cubitt of Norfolk in 1807

Post mill The earliest type of European mill, which was mounted on a post, around which the whole mill turned to turn the sails into wind

Provender mill A freestanding cast-iron mill first driven by steam and then by gas

Quant The shaft that turns the runner stone. Usually square to shake the grain in

Runner stone The top millstone, which turns

Sack hoist Wind-powered mechanism for lifting sacks of grain to the top of the mill

Shoe This feeds grain from the hopper into the eye of the runner stone

Smock mill Wooden mill, usually hexagonal or octagonal, with a cap that rotates to turn the sails into wind

Spilling the wind Opening the sail shutters to let wind through, usually as an automatic response to gusts

Spur wheel Large cog near the bottom of the upright shaft, which drives the stone nuts or other machinery gears. Also the name for any cog with teeth sticking out rather than up (crown wheel). Also called great spur wheel

Stone dressing The cutting of grooves on the grinding surface of the millstone

Stone nut Small cog at the top of the quant that transfers energy from the spur wheel to the stones

Tail-winded When the sails are facing the wrong way, and can be blown off!

Tentering gear Set of long levers which, with a turn of a screw, can lift or drop the heavy runner stone and so determine the fineness of the meal

Tower mill A tower of brick or stone containing mill machinery, with only the top (called the cap) and sails turning to face the wind

Under-driven A term meaning that the stones are driven by gears on the floor below 

Upright shaft The main shaft down the centre of the tower, taking power from the wallower at the top to the spur wheel near the stones

Vat The wooden casing enclosing the millstones

Wallower The first driven gear in a mill. It intersects with the brake wheel and transfers energy from the horizontal windshaft to the vertical upright shaft to drive the millstones

Windshaft The horizontal axle at the top of the mill, onto which the sails and the brake wheel are fastened by either a cross or a canister. The rod to control patent sails runs through the hollow centre