The emphasis is more on the manufacture of scythes than of plane irons, but the patent drawing does show a plane iron, and the patent title - as published in the annual patent-office report - mentions plane irons. The rather incoherent specification reads as follows. “Specification of a method of Making Scythes, Hay Knives and many other thin plate tools &c. discovered by me, Daniel Pettibone, as follows. Viz. - I weld the best of iron & tool steel together as usual in the common way, (less iron will be found to answer the purpose) and then make it to an exact thickness of plate by means of a tilt or hand hammer or a rolling mill - except a small reserve at one end and for the hook or crank to fasten it to the handles. How the plate is made - the back is formed (so as to give it near double the strength) with mould stamps, swages, or any other method to give impression and form a double back as the model.” The drawings - which are detailed and were made from the model after the 1836 fire - are more easily understood. The iron plate is rolled, using a special eccentrically shaped pair of rollers to a cross-section that is a sort of longitudinally-stretched sawtooth form. Each “tooth” is cut off to form the stock for one scythe or tapered plane iron. The detailed nature of the drawing, and the degree to which they depart from the written specification, suggests that this patent was important and well known to the patent examiners.

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USPTO pdf