[Illustration: Figure 58.--1827: THE BENCH PLANES exhibited at Philadelphia in 1876 were a radical departure from the traditional. In 1827 H. Knowles patented an iron-bodied bench plane that portended a change in form that would witness a substitution of steel for wood in all critical areas of the tool's construction, and easy adjustment of the cutting edge by a setscrew, and an increased flexibility that allowed one plane to be used for several purposes. (Wash drawing from the restored patent drawings, August 24, 1827, U.S. Patent Office, Record Group 241, the National Archives.)] [Illustration: Figure 59.--1857: THE ADDITION OF METALLIC PARTS to critical areas of wear as suggested by M.B. Tidey did not at first radically alter the design of the bench plane. (Wash drawing from U.S. Patent Office, March 24, 1857, Record Group 241, the National Archives.)] It is the plane, however, that best exemplifies the progress of tool design. In 1876, American planemakers were enthusiastically credited with having achieved "an important change in the structure of the tool."[16] Although change had been suggested by American patentees as early as the 1820's, mass production lagged until after the Civil War, and the use of this new tool form was not widespread outside of the United States. Hazard Knowles of Colchester, Connecticut, in 1827, patented a plane stock of cast iron which in many respects was a prototype of later Centennial models (fig. 58).[17] It is evident, even in its earliest manifestation, that the quest for improvement of the bench plane did not alter its sound design. In 1857, M.B. Tidey (fig. 59) listed several of the goals that motivated planemakers: First to simplify the manufacturing of planes; second to render them more durable; third to retain a uniform mouth; fourth to obviate their clogging; and fifth the retention of the essential part of the plane when the stock is worn out.[18] By far the greatest number of patents was concerned with perfecting an adjustable plane iron and methods of constructing the sole of a plane so that it would always be "true." Obviously the use of metal rather than the older medium, wood, was a natural step, but in the process of changing from the wood to the iron-bodied bench plane there were many transitional suggestions that combined both materials. Seth Howes of South Chatham, Massachusetts, in U.S. patent 37,694, specified: This invention relates to an improvement in that class of planes which are commonly termed "bench-planes," comprising the foreplane, smoothing plane, jack plane, jointer, &c.