Abstract: A cast iron piston characterized by a pearlitic matrix microstructure comprises a ring groove defined by opposed faces that are selectively hardened adjacent the piston side wall. The hardened surfaces are characterized by a martensitic matrix microstructure having a Knoop hardness of preferably at least 690. In a preferred embodiment, the groove faces are hardened by a stripe hardening process.

Abstract: An inflation valve gauge including a tubular stem having an inner end connected to a pressurized chamber such as formed by a tire, and an outer end provided with an inflation valve; the stem being surrounded by a special, helically wound Bourdon type pressure gauge tube, having an axially inner end penetrating a wall of the tubular stem and an outer end having a pointer overlying an axially directed scale plate; the gauge tube being surrounded by a sleeve which supports the scale plate and is joined to the stem axially inward from the gauge tube; the convolutions of the gauge tube being disposed in close proximity, the confronting wall surfaces of the stem and sleeve being in close proximity to the convolutions of the gauge tube to restrain the gauge tube against extreme mechanical forces tending to damage the gauge tube.