Although there are several types of die structures, explanations provided here is based on the widely used movable stripper structure.
HOLDER S400, S50C (S55C), FC250, A7075
The punch and die holder not only fix the die to the press machine but also supports the rigidity of the die. They also adjust the die height and provide the space for springs, etc.
Generally, the materials used for punch and die, holder, are SS400 or S50C. There is not much difference between the two. Among cast iron types, FC250 is used. When high rigidity is required SKS3 is used after heat treatment. When low weight is required, the aluminium alloy A7075 can be used.
BACKING PLATE SK3, SK5, SKS3, AND S50C
Backing plates are used to back up so as to prevent components from getting too deep inside the holder due to the force of press operation, to prevent the parts from getting detached, and to adjust the height of the die. They are used at three locations in a die.
SK material is used after heat treatment for back up. When high rigidity is required SKS material is used. S50C is used without heat treatment, for backing up or preventing the detachment of parts or for adjusting the height.
PUNCH PLATE SS400, S50C/SS55C, SKS3, SKD11
A punch plate is used to hold a small punch. Generally, SS400 and S50C are used without heat treatment. Pre-hardened steel having a certain amount of hardness, or heat-treated SKS3 or SKD11 is used for high volume production.
STRIPPER PLATE S50C, SKS3, SKD11, PRE-HARDENED STEEL
While the main function of a stripper is to remove scrap, very frequently it is made to have important secondary functions of pressing the material or guiding the tip of the punch.
S50C or pre-hardened steel is used for a stripper, which does not require heat treatment. However, when a punch guide or a material-pressing member is added, SKS3 or SKD11 is used after heat treatment.
DIE PLATE SK MATERIALS, SKS3, SKD11
SK materials or SKS3 is used in dies for small volume production. However, the standard material used for making die plates is SKD11.
In dies, nested type plates are very frequently used. In the case of small volume production, S50C without heat treatment is used at times for the main plate. For medium or higher volume production, SKS3 or SKD11 are used after heat treatment.
SKS3, SKD11, SKH51, powdered high-speed tool steel; cemented carbide, etc. are normally used for punches.
However, SKD11 is the standard material used for making of punches. If the volume production is small SKS3 is sometimes used. When the size is small, or when toughness is requiredSKH51 is used. Powdered high-speed tool steel or cemented carbide are used when wear resistance is required or for large volume production.