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of metal thickness into the die, as indicated at Figure 8-3b. This penetration occurs before fracturing starts and reduces the cross-sectional area of metal through which the cut is

being made. Fracture will start in the reduced area at both upper and lower cutting edges, as indicated at Figure 8-3c. If the clearance is suitable for the material being cut, these

fractures will spread toward each other and eventually meet, causing complete separation. Further travel of the punch will carry the cut portion through the stock and into the die opening.

4.Why is necessary for proper clearance in shearing or cutting?

Proper Clearances between cutting edges enable the fractures to meet. The fractured portion of the sheared edge will have a clean appearance. For optimum finish of a cut edge, proper clearance is necessary and is a function of the type, thickness, and temper of the work material.

5.When the contour to be blanked is irregularly shaped, why must the center of pressure be

calculated?

Such irregularity results in a bending moment in the press ram, and undesirable deflections and misalignment. It is therefore necessary to find a point about which the summation of shearing forces will be symmetrical.

Doing the reading materials after the class.

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