Jesse Engineering Overhead Clamp
On traditional swing arm benders the clamp die is mounted on a carrier which, in turn, rests on a slide built into the top of a "swing-arm". (The arm assembly "swings" with the bend die's rotation.) In a swing arm bender, the clamp die, upon closure inherently induces a massive offset load onto the bend die. This can produce a tilt of the bend die. As the bend die rotates, this tilt will result in a continuously varying out-of-plane- relationship between the bend die and both the pressure die and wiper die. the older and the more worn the machine and/or its tooling, the worse the condition becomes.
When the bend die tilts under clamp loads, the upper portions of the clamp surface can actually pull away from the workpiece, resulting in a reduced clamping grip.
Because of the extremely high clamping and bending forces required in bending large and/or "critical" workpieces, this tilting phenomenon has long necessitated the use of such devices as overhead tie bars, center-posts, multiple hold-down bolt patterns, and flange mounted bend dies on swing arm benders.
The toggle type clamp closure mechanism used on most swing arm benders necessarily generates an indeterminate excessive clamping force at its dead-center position before it reaches its over-dead-center locked-up position.
Because it is only an hydraulically actuated mechanical device, it is not possible to use hydraulic pressure gauges to measure the true clamping forces imposed by this device.