IT IS A MUST TO TAKE THE TOOL OUT OF THE HOLE FOR EVEN IF YOU POUR WATER, THE WATER WON'T REACH THE FRONT-MOST PART WHICH MAY BE OVERHEATED! Show this video to teach workers how to operate. Though the speed of flex rotation is higher, the drilling technology is essentially the same. We recommend to use a flex with adjustable rotation and to operate between 4000 and 6000 rotations.