A clamp for connecting flanged tubes comprising a pair of tangs having a tampered groove around their insides to engage the flanges. One of the tangs is provided with a pivotally connected screw, which passes through an aperture in one end. A nut attached to the screw holds the tangs in position. To prevent rotation of the tang about the screw, the lower shaft of the screw is provided in a non-circular shape, with the aperture in the tang being provided in mating conformity.