1. Touch test
Wipe the surface of the outer covering with a clean piece of gauze. ​Inspectors should wear contact gloves and touch the stamping part vertically, close to the stamping surface. This method of testing depends on the experience of the inspector. Suspected areas can be polished with a whetstone and verified if necessary, but this method can be an effective and rapid test.

2. Oil coating inspection
Wipe the surface of the outer covering with a clean gauze. Use a clean brush to spread the oil evenly over the entire outer surface of the stamping section in the same direction. Examine the oiled stamping parts under a strong light. It is recommended that the stamping parts be placed upright in the body position. With this method, it is easy to find tiny punctures, indentations, ponds, and ripples on the stamping site.

3. Polishing of flexible gauze.
Wipe the surface of the outer covering with a clean gauze. By grinding the surface of the stamp with a flexible mesh of sand all over the surface, any pits and indentations will be easily detected.

4. Whetstone polishing
1) First wipe the surface of the outer covering piece with clean gauze, and then polish the surface with whetstone (20×20×100mm or larger). Polish the areas with arcs and hard-to-reach areas with relatively small whetstone (for example: 8×100mm semi-circular whetstone).

2) The choice of whetstone particle size depends on the surface condition (such as roughness, galvanized, etc.). Fine-grained whetstone is recommended. The direction of the whetstone grinding is essentially longitudinal, and fits well on the surface of the stamping part. Some special spots can also complement the transverse grind.

5. Visual inspection
Visual inspection is mainly used to discover abnormal appearance and macroscopic defects in stamping parts.

6. Instrument testing
Insert the stamping part into the tool and check the stamping part against the operating requirements of the tool manual.