This spring loaded welding clamp from Strong Hand Tools can be easily operated with one hand and the magnetic v pad will adjust to fit almost any shape.
The MagSpring is available in 75mm (3") and 115mm (4 1/2") options.
Model: UDV45M
Capacity: 75mm (3")
Clamping pressure: 227kg
Weight: 0.4kg
Model: UDV65M
Capacity: 115mm (4 1/2")
Clamping pressure: 227kg
Weight 0.5kg
