In Expanding, a precisely made multi-sided wedge shaped driver-drawbar is forced into a set of segmented master jaws to produce the radially outward acting expanding force. In Shrinking, an external drive ring is forced over segmented jaws to produce the inward die movement. The jaws are mounted on a heavy steel table and trained and guided by radial T-keys running in milled and gibbed slots, and carry interchangeable dies so that one basic machine can handle the widest varies of part sizes and shapes. The amount of die travel is absolutely repeatable, infinitely adjustable over the specific range, and easily and quickly readjustable to compensate for variations in spring back, varying part sizes, etc. The Driver Force is developed by one or more double acting hydraulic cylinders supplied from a high pressure hydraulic power unit. The work piece, placed over the dies, is circumferentially stretched and permanently set to the predetermined size and shape. When properly applied, using correctly developed tooling, this process does not appreciably thin the metal of the work piece as the necessary material to provide for the increase in part diameter is drawn from the total length of blank, which shortens accordingly.

These machines, while somewhat simple in principle, require most careful design and construction to insure absolute concentricity's, parallelism, proper compound angle relationships, sufficient force, die clearances, etc. while at the same time having the strength and rigidity to operate under extremely high tensile and compressive loads, and unusually high bearing pressures.

These diagrams graphically show how the method works. Angles and elements have been greatly exaggerated in order to more clearly show the action.

1. How It's Done
2. The Advantages
3. What Kind Of Part Can Be Made
4. Limitations
5. Tooling
6. Controls
7. Operation
8. Flexibility
9. Consultation/Analysis
10. Investigate