The joint of formed U-stiffener should be finished thru holes on it.

welding machine

Drilling of U-stiffener

The joint of formed U-stiffener should be finished thru holes on it. For this reason, the U-stiffener should be fixed onto drilling fixture and drilled with the tool of radial driller. Upon finish of one side, the stiffener should be flipped to the side and drilled. It has high productivity and good accuracy.