Which angle is not to be changed while drill grinding?

The clearance angle, also known as the relief angle, should not be changed while drill grinding. This angle is crucial for allowing the cutting edges to clear the workpiece effectively and prevent binding. Maintaining the correct clearance angle ensures efficient cutting and enhances the lifespan of the drill bit. Adjusting other angles, such as the point angle or lip angle, can be beneficial for specific applications, but the clearance angle must remain constant.