Wooden Plane Throat Geometry

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6 thoughts on “Wooden Plane Throat Geometry

  1. Hey Bob,
    A nice breakdown of the geometry of planes. I think there might be another explanation though, for why 19th century American planemakers used such wide mouths.
    When we look at the double iron planes in the Seaton chest, we see tight mouths and nearly vertical wears. I’ve seen photos of a couple other early English planes that are made the same way, and my own experience is that this design affords the best shaving escapement. But to make a plane this way, the abutments have to be stopped cuts that end in the middle of the wear. It takes a lot of labor-intensive hand work.
    On the later wide-mouthed planes, however, the abutment is a through-cut that comes out of the mouth. This can be done by machine, which obviously speeds up production a lot. And I think that’s the main reason for the later design. Now, if the mouth is really wide, the wear needs to be at a lower angle, otherwise the opening at the top of the plane will be unusually large; on a small smoother, it would not leave much room to grab the front of the plane.
    Anyway, that’s my theory. I like your new(ish) wordpress site and am glad to see you blogging more frequently these days.

    – Steve

    • Thanks for chiming in Steve! This is exactly how my largest smoother (the one whose mouth is pictured above) was done. The wear on that plane is 80 degrees and the abutments dead end into the wear, just as you describe. It is an English common pitch (47 ½ degree) plane. When I got it the mouth was about half as wide as it is now (i.e. about 1/16″). However, because the wear is so steep, it has opened up about 1/16″ with just a minor amount of routine maintenance. I’m not sure the mouth on this plane was ever any tighter than 1/16″. However, even with a ⅛” wide mouth, it still works fine.

      I agree with you on the later planes as well. The English tended to resist industrialization and hold on to the quality hand work longer than Americans did. But as industrialization took hold the tools were modified to make them easier to mass produce by machine. Shame really.

      I’ve yet to decide how I’ll handle the double iron smoother I’m going to make. I’ll probably raise the wear to 80 degrees like the Seaton planes and my English double iron smoother. My shop is climate controlled so my plane soles don’t require re-truing very often. If they did I might decide on a lower wear angle. For the single iron I’ll likely try about 62 degrees for the wear like my little single iron English smoother has.

        • I don’t know who made it. The plane is unmarked. The iron is marked Aaron Hildick, Diamic (the same “Diamic” inside of a diamond mark used by Henry Taylor today). My guess is that it’s from the late 1800s. There were pencil marks on the bed and back of the wedge when I got it. I think they were the maker’s original # marks to keep the body and wedge together. Other than that there are no other marks on the body.

  2. Beautiful article Bob!! I hope you will film the whole process about building a smoother plane.I ‘m looking for beech , maple and oak in order to build my future planes…. so i need your instructions.

  3. Great insights! Now all I have to do is get to work on that lump of red beech I have sitting in the shop, only I haven’t really decided whether to do classic german or english – maybe even a Krenow. I guess the drawing board will be first stop. Keep it up!

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