Grindstones have been used since ancient times, to sharpen tools made of metal. They are usually made from
sandstone.
Grinding grooves , New South Wales, Australia Aboriginal grinding grooves, or axe-grinding grooves, have been found across the Australian continent. The working edge of the hatchet or axe was sharpened by rubbing it against an abrasive stone, eventually leading to the creation of a shallow
oval-shaped groove over time, The grooves vary in length from up to , and can be up to wide and deep. They are often found near water, which was sprinkled on the stone during grinding to reduce dust. 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, operated by a crank handle, is found in the
Carolingian manuscript known as the
Utrecht Psalter. This pen drawing from about 830 goes back to a late antique original. The
Luttrell Psalter, dating to around 1340, describes a grindstone rotated by two cranks, one at each end of its axle. Around 1480, the early medieval rotary grindstone was improved with a
treadle and
crank mechanism. == See also ==