NOTE: This is a living document and will see continued updates and adjustments as time permits.
A Calabria and Velvicut axe with the handles altered for ideal offset.
A beautiful ice blue scythe stone made for us in the USA to our specifications. 400 grit aluminum oxide with a medium-hard bond, this stone produces a finer edge than one might expect for its grit rating. Cuts fast, holds water well, resists glazing, is hard enough to bear down to realign rolled edges, and produces a very keen edge that easily dry shaves while retaining the “sticky” bite of a medium or coarse stone. Finer than any of our other scythe stones, yet no slower to hone with. We’re very impressed, and it’s exceeded our expectations for performance.
With stock crisp edges:
With dressed edges:
Note: This work is a living document and will continue to see updates as we have the opportunity to write them.
In cutting tools today the most common topics stem around steels, heat treatment, and (in folding knives) locking mechanisms. If you’re lucky, you might see some discussion around cross-sectional geometry and its impact on cutting performance. However, one aspect of edged tool design that seems to almost never be discussed is the impact of the profile of the tool on its optimum stroke pattern, or even how strokes themselves behave. This is a fundamental and profoundly important aspect of edged tool design, and culturing a deep understanding of it can greatly assist in matching the correct tools to their best functional contexts.
Any stroke of a rigid object consists of two variables: the path and the presentation. In the following diagrams, the path is shown as a red line, and for clarity’s sake the heel of the blade is bound to it, riding along it as if affixed to a track.
Presentation is the orientation of the blade relative to the path. A green line is used to represent the path traced by the toe of the blade and the depth of the swath made by the total stroke, though the red line is considered the dominant path of the two. In this case there is no path (just a single point at the heel) and the presentation of the blade is being altered by pivoting it at that point.
You can see how an object presented as a target to the blade would only be cut by this motion if it existed in the space between the first and second frames of the animation, after which the spine begins to precede the edge, and the edge is pulled away from the target instead of moving into it. This brings us to the subject of edge engagement and stroke optimization.
To begin, let’s demonstrate using this straight-edged knife cutting a target against a flat anvil surface. As before, the red line represents the path of the stroke, while the green line described by the toe helps visualize how the presentation of the blade is affecting the depth of the swath (the area the edge actively passes through during the stroke.) The act of cutting consists of a combination of pushing and sliding forces, in varied degrees. Here we see an isolation of sliding force, without any pushing.
As you can see, no green line is visible because the edge is running perfectly on top of the path itself, and as a result, there is no depth to the swath. In order for the knife to cut the target, the path and presentation need to be altered to add depth to the swath and place the target within its boundaries. However, the edge can be considered as fully engaged because its full length is sliding along the surface of the target, albeit with no penetration at all. This unusual situation will become important later as we delve into more complicated aspects of cutting strokes, and will be referred to as a “neutral slice” from this point onward.
Shifting from a neutral slice, let’s switch to the opposite extreme by rotating the path 90°. This happens to switch this blade to what is, from here on out, referred to as a “fully open” presentation, in that the depth of the swath cannot be increased any further. Rotating the blade in either direction would result in the depth of the swath narrowing, but would cause either the toe of the blade or the heel of the blade to be leading the stroke depending on the direction of rotation. Regardless of the shape of the edge itself, the fully open presentation will always create a swath as deep as the straight-line distance between the heel and the most distal point of the edge.
The problem here is that only a small part of the blade is doing all of the work, which–in addition to causing more wear on one region of the blade in repeated cuts–is less efficient than spreading out the work over more edge length. As an edge is effectively a slope, this is much like how climbers tackle otherwise unscalable inclines by zig-zagging up them. It stretches elevation over a longer distance, effectively making it like climbing a longer ramp to the same elevation. So let’s see what happens by altering the presentation of the blade to narrow the swath, bringing more edge to bear on the target.
This angled pushing cut is the same principle employed by the infamous guillotine, spreading the cutting force required over a longer length of edge than possible in a perpendicular cut. However, it obviously produces a notable limitation: you need to have empty space for the tool to pass into. This cut works fine if a target were hanging off the edge of a table, but if cutting in the middle of a broad, flat surface like a cutting board, you cannot force the handle through the board. A different approach would have to be used.
Let’s try “opening” the presentation of the blade relative to the path and trying a pure slice again.
Now we’re getting somewhere. We’re now able to engage the full length of the edge in the stroke. However, you may notice that there’s now little room for the hand, and if the edge didn’t sit so far forward of the handle we would have to lift the heel of the blade instead of the toe and make a drawing cut to provide this effect. Additionally, the anvil surface is no longer opposing the direction of force, and so isn’t lending a helping hand in immobilizing the target as we cut into it. Let’s try a combination of slicing and pushing forces instead.
The edge is now fully engaged with good clearance for the hand and the anvil surface is opposing the applied force from the cut, helping to immobilize the target as we cut into it. Chances are that this resembles the action of how you already use a knife in the kitchen, because it’s what you’ve found to provide the best results. Now you know why!
[To Be Continued]
A short story on scythe mowing prowess appearing in “The Industrial Enterprise” volume 16, 1909.
You’ve discovered that it has a few significant problems with it, right? Chances are the taper is noticeably irregular, the neck is as thick as a baseball bat, and you can’t get the nibs to loosen up despite knowing that they’re a left-handed thread because they were cranked on too tight at the factory. But here’s the good news: all of those issues are fixable.
The irregular taper and thick neck of the snath can be fixed with a little time with a spoke shave and rasp, and the nibs can be loosened by using some rubber vise jaw pads to hold the grips of the nibs tightly without marring or cracking them and using the shaft of the snath for leverage to break them loose. There’s one major flaw, however, that’s not as easy to correct…the collar is installed a whopping 20° out of alignment, and when the loop bolt is perpendicular to the ground like it should be, the arch of the snath is pointing right towards you.
It’s not a perfect fix, but you can correct for this by introducing a twist to the tang of your blade much like is commonly seen on European pattern blades. Heat the shank of the tang in same manner you would if you were adjusting its pitch, but instead, lock the tang in a sturdy vise and pull on the blade while the shank is still at heat to introduce a matching 20° twist to the tang. This will correct for the crooked collar to bring the arch of the snath back to vertical. The downside of this is that when adjusting the hang of your blade you’ll now be pivoting the length of the blade along a path that resembles an inverted cone instead of in a nice flat circle like you would with a snath that had the collar correctly mounted, but it’ll at least keep the arch from striking you in the thighs and knees every time you take a stroke with the scythe!
An initial proof of concept of the North Star snath. The snath is produced in two parts, and joined by an aluminum elbow. The halves in this case were both the same, but were technically both the upper half, as that was the component I received samples for. This resulted in too strong of a bend in the neck of the lower end, but the production version will have less severe of a curve.
The halves come overly long on purpose, allowing the user to trim them down to desired length. They can then be rotated in the aluminum coupling, allowing the snath to “shapeshift” to best adapt to the user’s preference before being drilled and bolted in its final position. This has the benefit of allowing for a truly one-size-fits-all scalable stemless snath, and allows the snath to pack down for transport or shipping. Note the strong lateral bend of the upper half. This both places the hand in a very ergonomic position, but the end can be used as a grip in its own right when lifting the lay of the blade while mowing, as circumstances sometimes dictate.
An illustrated brochure from scythe manufacturer Harvey Waters of Northbridge, Massachusetts, circa 1861, demonstrating his offered range of curvatures and describing their regional popularity for what kinds of terrain and growth. Mr. Waters has been credited with a number of manufacturing innovations, including the use of roll-forging as opposed to the typical use of trip hammers. A PDF form of this incredible document can be found HERE.
When analyzing knife and tool designs there are a wide range of approaches that can be used to develop an understanding of a particular tool’s ideal applications. One of these methods that I’m fond of using when initially sizing up a tool is the line test method. Imagining a superimposed straight line over various points of the tool’s outline is a quick and easy method for establishing rough concepts of tool clearance in use. That is to say, it helps you get an idea of how much space your hand will have in use, what regions of the blade will be making contact at what orientations relative to the target, and if any regions of the blade would be prevented from cutting against a broad flat surface. For instance, if you were cutting atop a chopping block of some kind, many forward curving blades would need to be chopping on a block of a certain height and width in order to deliver a blow along the interior of the blade’s arch without the hand striking the ground. To demonstrate this method, observe the differences between the following lineup when the test is applied.
To begin with, we’ll start the the most basic test–seeing what a line looks like describing a “table” surface, and what the tool would look like laying against it with one point of contact somewhere on the blade and one somewhere on the handle. This is the same as placing the tip of the blade on a table surface and rolling it back until the handle contacted it.
The line test can also be used to assess things like what part of the blade will be in contact with a surface when held at a given angle to it. This is often useful when considering specific task applications where the target will have a certain spacial relationship to the user. I often think of it in terms of if the target will be sitting above or below the elbow, and by how much. The following images show one example of the line test being used to approximate the angle at which the tip contacts the plane surface. However, if you have a particular set of tasks in mind for a knife, imagine the plane formed by a “line of best fit” by your targets and try using the line test at those angles to see if an appropriate region of the blade is being contacted.