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The file blade has many wedge-shaped teeth. It is pressed onto the workpiece and pushed forward at the same time so that the teeth are penetrating into the material removing chips.
Figure 23 Action of the milled file
Milled files have very sharp teeth with a small angle of wedge (47 degrees) and work with positive rake angle - the teeth have a forward inclination. This results in a cutting action which is suitable for soft material.
Figure 24 Action of the chiseled file
Chiseled files have teeth with big angle of wedge (70 degrees) and work with negative rake angle. This results in a shaving action which is suitable for hard material.
Note:
For fine finishing of faces the file may be slightly chalked. The chalk will deposit in the tooth gullet reducing the depth of penetration of the teeth.Fine chips, which would otherwise destroy the smooth surface of the workpiece, settle in this chalk layer.
Figure 25 Chalked chiseled
file
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