1. Knife material must be fixed well, can not move, with the hole to a 90 degree angle 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) 3. Do not be too hard up and down the screw, so as not to screw the screw 4. If there is a condition, you can add coolant, when it is about to drill through, pay attention to slow down into the speed, if abnormal or when poor chip removal, please stop working, the iron work clean up<br><br>Cutting Diameter:22mm Suitable for cutting material:Aluminum Doors & Windows Water Pump Drilling machines Sainless steel plate steel castings, aluminum alloy and other metal plate Colour:As Shown Material:Cemented Carbide<br><br>Package Contents: 6 x Metal Hole Opener 22mm<br><br>Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.