Abstract: An object of this invention is to increase strength of the turret plate and to disclose new constitution of a cover portion, a grinding device is constituted of a rotate fly-wheel; a turret plate which is located face to face with the fly-wheel and rotates in synchronization with said fly-wheel, said turret plates being formed in a cross shape with a plurality of leg portions extending in a radial direction thereof; a plurality of grind tubs located rotatably or oscillatably between said fly-wheel and vicinities of front ends of said leg portions of said turret plate, each of which has an opening portion above thereof, a periphery portion of said opening portion in said grind tub provided on said leg portion at a position ending horizontally positioning above said leg portion at a horizontally extending position; a cover portion installable to said opening portion of said grind tub by sliding; a fix means provided between the cover portion and the grind tub; and a reinforcement means provided on the turret pl