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1) because of heat softening, tooling will wear down.
2) Because of mechanical friction, front surface of tooling with chips, back surface of tooling and workpiece, all these has a friction, then cause wear down.
Factors ,which will effect the wearing capacity
1) The higher the temperature, the bigger the wearing capacity.
2) The hardness of the tooling is high, material is fine and uniformly, the abrasion performance is good.
3) The strength of workpiece material, small heat conductivity and the surface is easy to harden, so the wearing capacity is big.
Wearing condition
1) there is a flashlight on the workpiece surface, the tooling is rough.
2) A small gap on the drill bit.
3) The hole diameter of the workpiece has a little change.
4) There is shakeness and noisy.
5) The shape of iron and color have changed.
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