LAND AND ANGULAR CLEARANCE
Land:
The inner walls of the die opening are not usually made straight through.
If they are straight,the blanks or slugs tend to get jammed inside the die opening.This may lead to the breakage of punch or die.
To avoid this,the die walls are kept straight only to a certain dimension from the cutting edge.The straight wall is called as land.
LAND=3mm for sheet thickness upto 3mm and for thicker material equal to the sheet thickness.
Angular clearance
The die walls below the land are relieved at an angle for the purpose of enabling blanks of slugs to clear the die.
Soft material require greater angular clearance than hard materials.
The normal value of angular clearance is 1.5 Degree per side.
Dies for materials like silicon steel and stainless steel are privided with angular clearance from the cutting edge.(no land is privided).These materials are abrasive in nature and tend to bell-mouth the die opening rapidly if land is provided.