Nibbler assembly for punch press and method of forming elongated hole in sheet material

A method of forming an elongated hole in a sheet material, comprising the steps of:

• providing a die and a punch, the die including a through opening formed therein, the through opening having an oblong configuration as viewed along a vertical direction, the die including an upper surface formed with a recess extending from an upper peripheral portion of the through opening at an upstream side of the feed direction towards the upstream of the feed direction, the recess being dented downwardly relative to other portions of the upper surface, and the punch including a blade substantially matching in shape with the through opening and configured to enter the through opening, the blade including an upstream end portion in the feed direction provided with opposite corners each having an arcuate shape as viewed along the vertical direction;
• and
• driving the punch to punch in the sheet material successive holes such that the successive holes at least partially overlap with each other along the feed direction so as to perform a nibbling operation that forms the elongated hole in the sheet material.

A punch usable in combination with a die to punch in a sheet material successive holes that at least partially overlap with each other along a feed direction in which the sheet material is fed from an upstream to a downstream thereof, to perform a nibbling operation that forms an elongated hole in the sheet material, the die including a through opening formed therein, the through opening having an oblong configuration as viewed along a vertical direction, the punch comprising:

• a blade substantially matching in shape with the through opening and configured to enter the through opening, the blade including an upstream end portion in the feed direction provided with opposite corners each having an arcuate shape as viewed along the vertical direction.