This question was posed by a Japanese customer who was experiencing some chipping on the cutting edges of his dies. We asked that he submit some pictures via email so we could evaluate the issues.
Here's what we found out:
1. The customer was using a gang of four ASTM D-624-C Tear Test Specimen Dies mounted to a plate with minimal space between the dies so he could get good yield on his material
2. The dies were used on a "clicker" press; i.e., a swing arm cantilevered head that pushes the dies through the sample material and into a plastic cutting surface
3. Close examination of the die pictures clearly showed marks on the side wall of the dies indicating the material was pushed nearly �" up the edges of the dies. Pictures of the plastic cutting pad showed deep die penetration into the pad
4. Subsequent correspondence with the customer to discuss our findings confirmed
a. They were trying to cut three layers of a fairly dense material
b. The pressure setting on the press was set too high, causing the dies to drive too deeply into the cutting pad
5. WE RECOMMENDED that the customer restrict the technician to cutting only ONE LAYER of material because
a. Multiple plies of material will distort and no two pieces will be exactly the same
b. Multiple plies may give multiple Tensile and/or Tear Test results/readings
6. WE RECOMMENDED that the pressure setting on the press be adjusted
a. To "just" cut the material
b. Make as little impression on the cutting pad as possible
c. Maintain the cutting pad in a level and clean condition