1. Knife material must be fixed well, can not move, with the hole to a 90 degree angle 3. Do not be too hard up and down the screw, so as not to screw the screw 2. Just started drilling slowly contact with the material being drilled, can not impact the workpiece, at the same time for low speed (the larger the lower the speed of the hole opener) 4. If there is a condition, you can add coolant, when it is about to drill through, pay attention to into the speed, if abnormal or when poor chip removal, please stop working, the iron work clean up, Manufacturer: Akfldms