Squeezing is a quick and widely used way of forming ductile metals. Of the different processes of squeezing, cold heading and rotary swaging are very common.
Cold heading. Cold heading is a cold forging process, used primarily for the manufacture of bolts, screws, rivets, nails, and similar items. Materials in bar form is fed into the machine, where it is cut to length, held in a pair of jaws, and subjected to two or three blows to rough form the head. For complex shapes, or greater accuracy, the part is then repositioned in another die for final shaping or sizing. Bolt making machines combine thread rolling with cold heading to produce a complete bolt. A material to be cold headed must be ductile.
Thread rolling is a mass-production method for producing threads. It is a cold-working process, and is usually designed for automatic operation. The rolls have the thread form cut on their surface. The rolls rotate and are fed into the blank under pressure ; metal flows into a die shape forming a thread. The threading dies may be in the form of flat plates. These have a reciprocating action, the blank being rolled between them to form the thread.
Rotary Swaging. Rotary swaging is the process used to reduce the cross-sectional area of rods and tubes. Swaging is often accepted of as a cold-forging operation, because the metal - forming takes place under the hammering blows of die sections. The swaging machine consists mainly of a hollow spindle which carries the die sections.
The die is inserted in the slot in a spindle, rotated, and forced together repeatedly by the rollers around the periphery, as much as several thousand times a minute, forming taper on the work.
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