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3 Fundamentals of press design

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348 Sheet metal forming and blanking<br />

Table 4.7.2: Achieveable tolerances in fine blanking<br />

Sheet metal<br />

thickness [mm]<br />

Tensile strength up to 500 N/mm 2<br />

Inside<br />

contours<br />

ISO<br />

quality<br />

Outside<br />

contours<br />

ISO<br />

quality<br />

Hole<br />

distance<br />

tolerances<br />

[mm]<br />

Tensile strength over 500 N/mm 2<br />

Inside<br />

contours<br />

ISO<br />

quality<br />

Outside<br />

contours<br />

ISO<br />

quality<br />

Hole<br />

distance<br />

tolerances<br />

[mm]<br />

0.5 to 1 6 to 7 7 ± 0.01 7 8 ± 0.01<br />

1 to 2 7 7 ± 0.015 7 to 8 8 ± 0.015<br />

2 to 3 7 7 ± 0.02 8 8 ± 0.02<br />

3 to 4 7 8 ± 0.02 8 9 ± 0.03<br />

4 to 5 7 to 8 8 ± 0.03 8 9 ± 0.03<br />

5 to 6 8 9 ± 0.03 8 to 9 9 ± 0.03<br />

> 6 8 to 9 9 ± 0.03 9 9 ± 0.03<br />

The die-roll with its width b E and height h E depends on a variety <strong>of</strong><br />

blank and material-related factors (Fig. 4.7.8, 4.7.16 and 4.7.18). The<br />

angle and radius <strong>of</strong> inward and outward pointing corners, the material<br />

and the microstructure, strength and sheet metal thickness, for instance,<br />

exert a considerable influence. Also important in determining the dieroll<br />

amount is the edge preparation <strong>of</strong> the blanking plate and inner form<br />

Fig. 4.7.17 Example dimensions for a fine blanked part in accordance with VDI 3345<br />

Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998

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