... the principium form donkey turn a millstone , a donkey or a horse and a cattle,s strength to bolt ... 35-45cm, in center drilled a hole aout 10-12cm to install a vertical axis.stone roller,It's ... frame that closer outside ( outer box) drilled a hole of horizontal direction(main jack), the diameter ... inside centre part of two thick frame both install iron conical groove to corresponding stone roller,s ...