Abstract: Apparatus for localized radial expansion of a ductile metal tube into tight engagement with a tube support sheet, e.g., for deformable member which is axially compressed by hydraulic pressure to effect radial expansion of the deformable member and the tube. The hydraulic pressure is multiplied to provide a relatively high force in a small diameter by connecting a plurality of pistons in series by rigid connecting rods having axial and radial bores for flow of pressurized fluid. The apparatus carries a probe for locating the position of the tube support sheet and a support member carrying an eccentric cam. Rotation by an operator of the support member, by rotation of a rod passing therethrough, causes the cam to frictionally engage the tube wall and wedge the support member in position to provide an abutment surface for contact by a stop member on the rod, thereby positioning the deformable member at the desired axial location to effect radial expansion of the tube.