Machinery's Handbook, 31st Edition
Cutoff and Parting
1409
Line of cutting
Blank
Strip
Line of cutting
Blank
Scrap
Strip
Blank
Line of cutting
Strip
Line of cutting
Blank
Scrap
Strip Fig. 5. Types of Cutoff
Parting.— Parting is a cutting operation of a sheet metal strip by a die with cutting edges on two opposite sides. During parting, some amount of scrap is produced, as shown in Fig. 6. This might be required when the blank outline is not a regular shape and is precluded from perfectly nesting on the strip. Thus, parting is not as efficient an operation as cutoff.
Line of cutting
Blank
Strip
Scrap Scrap
Blank
Line of cutting
Strip
Fig. 6. Types of Parting Blanking and Punching
Blanking and punching are fabricating processes used to cut materials into forms by the use of a die. Major variables in these processes are as follows: the punch force, the speed of the punch, the surface condition and materials of the punch and die, the condition of the blade edge of the punch and die, the lubricant, and the amount of clearance. In blanking, a workpiece is removed from the primary material strip or sheet when it is punched. The material that is removed is the new workpiece or blank. Punching is a fabri cating process that removes a scrap slug from the workpiece each time a punch enters the punching die. This process leaves a hole in the workpiece (Fig. 7).
Workpiece
Workpiece
Blanking
Punching
Fig. 7. Blanking and Punching
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