Blanking, piercing and bending operations

As previously stated, blanking is the production of an external shape from sheet metal. In its simplest form, thus operation requires one punch and die. 

For simple blanking from strip fed by hand, the press tool consists of a die on top of which are attached the strip guides and the stripper plate. The punch is held in the punch plate. The arrangement is shown in section in Fig. 16.14. 

To assist in setting up and for subsequent operation, stops are required. For setting up, a sliding stop is pushed in and the strip of work material is pushed against it by hand. Fig. 16.15(a). The punch descends and blanks the first part, the blank falling 

Where the required workpiece is to have both an external and an internal shape - e.g. a washer - the two operations, i.e. blanking and piercing, can be done by the same press tool. This type of press tool is known as a follow-on tool. 

The principle Is the same as for simple blanking but the punch plate has two punches fitted - one for blanking and one for piercing - and there are two holes of the required shape in the die. Fig. 16.16. The work material Is again in the form of strip, fed by hand. 

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