60s plastic parts

This is part of the action for one note from a 1969 piano action. This was relatively early days in the use of plastics for piano action parts. This action had become stiff and sluggish. Examination showed the cause to be tight centres. The parts in a piano action move in little “hinges” called flanges. A metal centre pin (generally nickeled bronze) rotates in a hole bushed with special cloth. In this piano the jacks (the upright part in the middle) rotated freely, but all other centres were tight. The jack centres rotate in wood flanges, and all the others in plastic.
Discussion online brought to light that these early plastic parts are undergoing some continuing “curing” process that is causing them to swell. Other technicians working with the same type of action from the same period report a similar phenomenon.

In this instance, use of a special lubricant designed for piano action centres, was sufficient to get the action playing again reasonably well. But if this swelling process continues, the bushings will get too tight. The best solution in that event, is to replace all the plastic flanges with modern ones, probably wooden. (Modern plastic materials, however, are much superior to their early counterparts, and are found in some very classy piano actions).