Grindstone 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 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.