An Unusual Plane Configuration

Chronicle of the Early American Industries Association, Inc., The, Mar 2004 by Cox, J B

Recently, I found an Ohio Tool Co. smoother that seemed unusual. The wedge prongs were not formed, although the wedge body itself seemed to have been professionally made, and there was an iron wear plate let into the sole directly in front of the mouth, also professionally made in appearance. The single uncut iron is stamped OHIO TOOL CO./ CAST STEEL/ WARKANTED, and the toe is imprinted OHIO TOOL CO. (Figure I). Assembled in the conventional configuration (Figure 2), the mouth is extraordinarily wide, given the apparent little wear the plane has had (Figure O).

I showed the plane to Art Kushlan at a recent tool meet, and am indebted to him for his inspired assembly of the plane - with the wedge under the iron (Figure 3). When I asked Roger Smith, author of his opinion Transitional and Metallic Planes in America, for his opinion, he diplomatically, but pointedly, suggested I consult page 21 of his book on my tool bookshelf for identification and a brief discussion of this configuration.1 Now, having followed his advice, I am not apt to forget that Roger's important work on patented transitional and metallic planes contains information on wooden planes as well.

In a conventional wooden plane, the wedge is placed on Lop of the iron. However, the inverse configuration, in which the wedge is placed under the iron (Figure 3), forms a critical element in U.S. patent no. 12234, issued January 16, 1855, to W.C. Hopper of Pittsburgh, Pennsylvania.2 A picture of one of Hopper's planes and an artist's sketch of a cut-away view are shown in Roger's hook. (Guess which page!) In Roger's example, the iron has no marks, and W.C. HOPPER'S/ PATENT/1855 is imprinted on the toe. Having now identified my plane as one patented by a Pittsburgh maker and not simply as an unfinished Ohio Tool curiosity, it was logical to consult Charles Prine's work on makers in that vicinity.3 Prine discusses Hopper's business life, which includes seventeen years as a cabinetmaker, five of which were prior to his patent. So it is logical for Chuck to conclude Hopper saw the need for his invention, based on his cabinetmaker's experience.4 Chuck's book also includes Hopper's patent drawings.

In his patent, Hopper claims his invention is suitable for "fine work, where great smoothness of finish is required." Hopper achieves this by forming the cast iron "mouth piece" (Hopper's term for my "wear plate") with two "arms," one on each side projecting into the mouth, against which the toe side of the bedded iron rests (Figures 4 and 5). The mouth piece is cast to be the same width as the iron. When the iron is in place against the arms of the mouth piece, a narrow mouth is formed whose width is the distance between mouth piece arms and whose thickness is determined by the length of the mouth piece arms. Hopper's patent claims this very small throat (my plane measures 0.005 inches) "prevent[s] the plane [from] ripping or splintering the wood, even in the slightest degree [and] may be used even for planing veneers..." (Figure O). Further, the iron is held firmly against the plane body cheeks and anus by locating the wedge behind the iron so as to hear against the iron's entire hack, as Art Kushlan so brilliantly deduced (Figure 3).

The mouth piece is leveled with respect to the plane's sole by bearing against three "ad]usting screws" (again, Hopper's terminology) screwed into the plane body; and the mouth piece is held against the adjusting screws by the "screw" (no adjective here in Hopper's patent) passing through the mouth piece and up into the plane body. (Sec Figure 8, which shows the three adjusting screws in place; the center hole is for the month piece "screw")

Hopper's patent also claims an ingenious arrangement for wear compensation. As the plane's sole wears, it is necessary to sink the mouth piece. Rut if the mouth piece is sunk perpendicularly to the sole, the distance from the mouth piece arms to the iron will increase-in effect, widening the mouth. To compensate for wear without widening the mouth, Hopper cuts three important components at the same angle with respect to the front edge of the bedded iron: the mouth piece cavity; the angle of the month piece arms that face into the cavity; and the angle at which the mouth piece screw enters the plane body (Figures 4 and 5). Then, to compensate for wear, it is only necessary to resurface the sole, level the mouth piece with the adjusting screws, and replace the mouth piece. "[A]s the edge of the mouth piece which rests against the wall of its recess, as well as the wall ... itself is beveled, the mouth piece in sinking into its recess, is pushed forward toward the bit, just as far as the bit lias receded, and their relative position is exactly maintained, so the sides of the bit will rest as before against the projecting anus of the mouth piece."5 (Hopper uses the term "bit" rather than the more modern "iron.")

Thus, the sketch of the Hopper patent shown in Roger's book takes "artistic license" from the patent in two important respects. First, three adjusting screws are needed (as the patent and logic require), rather than the two illustrated in Roger's hook. Secondly, the "screw" is angled into the body, as specified in the patent, and visible in Figure 5, not screwed in at right angles, as shown in that artistic depiction.