Agrindstone, also known as grinding stone, is asharpening stone used forgrinding or sharpeningferrous tools, used since ancient times. Tools are sharpened by the stone's abrasive qualities that remove material from the tool through friction in order to create a fine edge. Similar tosandpaper, each stone has a different grit that will result in sharper or duller tools. In Australia,Aboriginal peoples createdgrinding grooves by repeated shaping ofstone axes againstoutcrops ofsandstone.
Grindstones have been used since ancient times, to sharpen tools made of metal. They are usually made fromsandstone.[1][2]
Aboriginal grinding grooves, or axe-grinding grooves, have been found across the Australian continent.[3] The working edge of the hatchet or axe was sharpened by rubbing it against an abrasive stone, eventually leading to the creation of a shallowoval-shaped groove over time,[4] The grooves vary in length from 80 mm (3.1 in) up to 500 mm (20 in), and can be up to 200 mm (7.9 in) wide and 100 mm (3.9 in) deep. They are often found near water, which was sprinkled on the stone during grinding to reduce dust.[3]
Grindstone machines work by spinning a circular piece of stone around its center point. These machines usually have pedals for speeding up and slowing down the stone to control the sharpening process. The earliest known representation of a rotary grindstone,[6] operated by a crank handle, is found in theCarolingian manuscript known as theUtrecht Psalter. This pen drawing from about 830 goes back to a late antique original.[7] TheLuttrell Psalter, dating to around 1340, describes a grindstone rotated by two cranks, one at each end of its axle.[8] Around 1480, the early medieval rotary grindstone was improved with atreadle andcrank mechanism.[9]
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