Tube clamping assembly

The present invention is directed to methods and apparatuses for clamping cylindrical workpieces, and more particularly, to methods and apparatuses for clamping and retaining cylindrical workpieces during orbital welding operations. A tube clamping assembly comprising a first portion having a base and a clamping device carried on the base, and a second portion having a base and a clamping device carried on the base. The first and second portions are coupled to each other such that the portions may be adjusted relative each other. In another embodiment, the invention is a tube clamping assembly comprising a base, and a first movable clamp arm and a first stationary clamp arm coupled to the base for gripping a cylindrical workpiece therebetween. The tube clamping assembly further comprises a second movable clamp arm and a second stationary clamp arm coupled to the base for gripping a cylindrical workpiece therebetween, wherein at least one of the stationary clamp arms is removably coupled to the base. In another embodiment, the invention is a tube clamping assembly comprising a base, a first clamping device carried on the base, a second clamping device carried oil the base, and locking means for limiting the outward axial movement of the first and second pair of clamping devices. In yet another embodiment, the invention is a collet for clamping a cylindrical workpiece, the collet comprising a pair of clamp parts each having a clamp surface adapted to engage opposing sides of the workpiece, each clamp surface being generally shaped as half a polygon in side view having at least six sides.