Features: This is a manual hydraulic metalworking hole punch used to open holes on steel plate. Dies are made from high quality 40 chromium steel for high hardness and long service life. Comes with 10 dies of 16mm, 20mm, 26.2mm, 32.6mm, 39mm, 51mm, 63mm, 76mm, 89mm, 101mm that can open different size of holes. Well packed and assorted in a metal box for well protection, convenient storage and carry. Drill a hole on steel plate first, make sure the screw rod can pass the hole then you can use this hole punch tool. Use small screw rod for opening 16mm, 20mm and 26.2mm holes, and large one for others. Specifications: Die Materiel: 40 chromium steel Dies: 16mm, 20mm, 26.2mm, 32.6mm, 39mm, 51mm, 63mm, 76mm, 89mm, 101mm Stroke: 20mm Suitable Steel Plate Thickness: ≤4mm Suitable Stainless Steel Thickness: ≤2mm Item Weight: 22kg Package Includes: 1 set x Hole Punch Tool & Dies Problem and Solution: P: Piston can not be opened; it is not moving and looks like stuck. S: Tighten oil return switch, and knock a few times on the middle part of oil return switch with a small hammer. Then press handle quickly for more than ten times. Try this solution a few times till the air inside is empty and problem will be solved. .