A pencil for electrosurgical generators includes a push button switch structure useful in selectively bridging spaced printed circuit contacts in spite of oxidized film on the contact surface. A movable concave disk has a sharp peripheral edge that is forced against the contact surface during switch actuation to cut through the oxidized film and reliably bridge the contacts. The disk is carried by an axial projection forming part of a resilient dome surrounding the projection. The dome includes a radial flange which is compressed against the printed circuit board by an annular member projecting axially inwardly from the housing wall around the outside of the dome. The closed end of the dome is connected to the flange by a frusto-conical connecting wall adapted to flex to permit the closed dome end to be pushed toward the open dome end during switch actuation.