The following questions should be asked when selecting the correct steel to use:
What is the thickness of the material and how many layers are to be cut?
The thickness of the material and the number of the layers to be cut determine the height and the thickness of the exact punching tool steel required. A tool height of 19 mm is used on a single-layered press, as upper leather is mostly pressed in single layers. Therefore, mis-punched parts can be spared and it also limits an "open" design of tool.
When determining a suitable cutting tool height, it is to be considered if, and in which height, the stay bars are welded on the tooling.
When the stay bars are welded, the remaining space must therefore be higher than the layers of material to be cut. Normally, up to 15mm of material can be cut with a tool height of 32mm. Tool heights of up to 50mm are used for thicker material.
Do the moulds have many corners? Is the mould very complicated?
The smaller and more complicated a cutting mould is, therefore the thinner the steel should be. An advantage is: a mould which has more flexion when cutting is more stabile than a mould with less flexion.
Should symmetrical parts be cut?
If a right and left part are to be cut with a mould (shoes, gloves,....), double edged punching tool steel is used. Only one mould needs to be produced, as two parts with the same mould can be cut.
Should the finished parts be automatically ejected?
If an ejection rubber needs to be mounted on a mould, the tool height must be appropriately selected so that there is enough space available for the ejection rubber and material to be cut during cutting. Otherwise, the material to be cut and the ejection rubber could possibly move sideways when compressed. The pressure on the material to be cut could subsequently be so strong that the welding points break or the mould will be warped. Stay bars must be welded in such a way that they are completely on the non-cutting edge. Therefore, the ejection rubber can be mounted above them.
What is the thickness of the material based on?
The cutting mould and the material to be cut are the deciding factors for the thickness of the profile. The thickness of the profile must be defined before every use.