Hole Size


One of the main factors in perforation by turret punch press or perforator machine is the hole size. The hole size is determined by its diameter for a round hole. For other type of holes, the hole size is determined by the diameter of a circle drawn from the centre point of the hole to the outer edge of the hole shape.

There is a general rule that the hole size should be equal to or greater than the material’s thickness. Often, in fact, the ratio 1-to-1 between the hole size and material thickness is not adequate. The ratio 1-to-1 is probably true only for soft material such as mild steel or soft aluminum.

On the other hand, for harder material such as stainless steel, the hole size should be twice the material’s thickness or even larger. A bigger hole will result in safer, more accurate perforated sheet metal and it will be easier to manufacture. Moreover, the larger hole will reduce the risk of punching tool failure during the perforating process well as lengthen the tool life.

calculating hole size for different punching tool

The illustration above shows many common types of punching holes (standard and non-standard).
The black thick line identifies the shape of the hole and the blue circle identifies the outer edge of the hole. The red line identifies the hole size which will be evaluated against the material thickness