Patent ID: 8052028

Claim:
A device for use with a welding apparatus, comprising: a housing component; a movable component being at least partially located in the housing component and having a discontinuous contact surface for contacting a work piece and a central opening for accommodating the welding apparatus, the discontinuous contact surface includes a plurality of separate surfaces that surround the central opening and are interrupted by intervening spaces such that the discontinuous contact surface does not circumferentially enclose the central opening; a biasing component being at least partially located in the housing component; and a two-piece back stop that includes a stationary annular component that is attached to the housing component, and an adjustable annular component that is connected to the housing component and can be adjusted to affect the force exerted by the biasing component, wherein during operation the welding apparatus is advanced towards the work piece so that the discontinuous contact surface contacts the work piece and urges the movable component into the housing component against the force of the biasing component.