For what seemingly domestic purpose was the first American patent for a *steel* coil spring in 1857 initially used?

Answer

Chair seats

The shift to mass-producible, durable springs required the standardization of spring steel, driven by the Industrial Revolution. While Tradwell patented the coil concept earlier, the first patent in America for a true *steel* coil spring, intended for widespread manufacturing applications, arrived in 1857. Surprisingly, its initial designated use was for chair seats. This application highlighted the growing manufacturing capability that allowed for the mass production of consistent steel coils, moving away from the slow, manual process of winding springs on an arbor, and setting the stage for larger industrial uses.

For what seemingly domestic purpose was the first American patent for a *steel* coil spring in 1857 initially used?
inventionMetalspring