Dies are reground when the cutting edge part is worn out (increase in the number of burrs) thereby regenerating the cutting edge. The methods of regrinding a die are - the method of grinding the entire plate and the method of grinding only the insert part. In the method of grinding the entire plate, although the plate becomes thin every time it is ground, there is no particular problem because even the insert parts such as button dies change at the same level. In the method of grinding only the insert parts, it is necessary to adjust the level to which the grinding is made. If this adjustment is not good, undulations appear in the plate surface, and this will affect the product quality. Therefore, as shown in Fig. 1, it is made easy to carry out adjustment of the level of the button dies.

In a button die without a flange as in (a), there is no particular problem because it is possible to adjust by placing a spacer to the extent of grinding. In a button die with a flange as in (b), it is necessary to place a spacer above the flange. While the number of spacers increases as the number regrindings increases, it is not good when they become too many. The spacers should be only up to about 3 to 4, and when their number becomes large, their thicknesses are increased so that their number does not increase.

Next, we discuss the relationship between the hole diameter (d) and the height (L) of the button die. When the dimension L becomes too long compared to the hole diameter, it becomes easy for scrap clogging to occur. Since this problem is particularly easy to occur in the case of small hole diameters, it is good to make it as short as possible. Considering the relationship with other machinings, the plate becomes thick and the length of the button die becomes too long compared to the hole diameter. When it is felt that the balance between the hole diameter and the length of the button die is poor, it may be good to adjust the length of the button die by placing a collar behind the button die as shown in Fig. 2.

In hole punching using a button die, very often the hole shape is simple, and there is the trend of easy pulling up of scrap. As a countermeasure, there is a button die that prevents pulling up of scrap. This structure is shown in Fig. 3.

In hole punching operations, there is no effect on the operation even if there is slight change in the clearance of the straight part or curved part shape. Further, shape of the hole punching is that of the punch and the shape of the punched part is that of the die. The scrap pulling up preventing button die is one that has utilized this principle. The clearance is widened at a part of the die and a groove is prepared. This groove is made to be inclined. Many such grooves are prepared. The blanked shape is that of the die cutting edge shape. The blanking scrap moves vertically. Therefore, the projected shape of the inclined groove is a shape that climbs over the inclined groove, and hence increases the biting of the die. This biting force prevents the pulling up of the scrap. However, the effect is small in the case of hard materials such as SK materials or in the case of very thin materials.