The worn bit can be tested by template test after grinding, but visual inspection is often used in many factories for convenience.

So how do you test it visually?

First of all, the cutting part of the bit is erected upward with two eyes at eye level. Since the two main cutting edges of the bit will produce parallax in front of each other, it is often felt that the two cutting edges will look higher and lower. Rotate the drill 180 degrees more times when looking at the head, if the results are the same, the symmetry will be shown. Same thing for the lip relief angle, same angle of inclination. Since the bit is grinded by hand, it needs to be inspected after it is polished.

If the drill bit grinding machine is used, the grinding bit will be more accurate and the grinding bit will be more standard. The grinded bit shall be tested and used after qualified.