Hay knives aren't obsolete in the slightest, but are no longer made. I use one every few days for cutting portions from round bales. If you think that a chainsaw works better then you haven't used one in good operating condition. They work fast and with little effort. The "Lightning" or "Weymouth pattern" hey knife was most emphatically not an English invention, but rather an American one--specifically that of a George F. Weymouth March 7, 1871, of Maine. They were first made by the Hiram Holt Mfg. Co. of East Wilton, ME. The English pattern hay knife looks rather different, with a single canted handle and a blade resembling an overgrown chef's knife of sorts.
Here's a scan from an 1893 illustrated David Wadsworth & Son (of Auburn, NY) that shows both a Weymouth pattern hay knife and a few sizes of English pattern hay knives.
Hay knives were also often used for cutting straw, peat, and sod. The teeth of the Weymouth pattern were ground hollow on a grinding wheel and easily slice through even densely packed hay. It was not until roughly the 1980's that baling became the overwhelmingly dominant method of hay storage, and up until that point in time the hay knife remained in faithful service. Later on, hay knives were made with adjustable handles and replaceable blades, many of which used sickle bar mower blades for the purpose. They were still in manufacture at least up until the 1930's and references suggesting their use (in a non-historical perspective) abound up through the late 1950's and beyond.
I guess my understanding of it was off (thanks for giving repair to that). I had bought a hay knife a few years back at a yard sale (along with a hog nose cant hook) and didn't know what it was. So I talked to the curator at our local museum (san lorenzo valley museum) to get my info. Either I got some inaccurate information or this long removed from when I learned about this my recollection of the information was bad (probably a bit of both). I did end up selling it for $40 dollars. As well as the cant hook I picked up with it for another $40 (the two I had bought from that yard sale for the grand total of $4).
Any way I think it still counts as an obsolete blade. You said yourself that they are no longer manufactured and that the process they were used in has changed to where it no longer requires them. And a lot of people probably have not seen one before. Even the farmer I sold it to as wall art even said he had never heard of it until he saw my listing. And that he wanted it as a conversation piece relevant to his living.
