Abstract: The invention relates to a fixture that reduces the heat transfer between a thermally conductive work piece, such as a copper tube, and the fixture. In one embodiment, the fixture includes a pair of collet members, with each collet member having at least one work piece engaging protrusion, and a clamping mechanism that urges the collet members toward each other to engage and clamp the work piece between the collet members. The contact between the work piece and the protrusions of the collet members inhibit additional surface contract between the work piece and the fixture, reducing the heat transfer from the work piece to the fixture during welding.