The “right” amount plane iron camber
Not another article on plane sharpening!
Sharpening a plane, or sharpening anything for that matter is always interesting to talk about. This is because so many people are so sure they have in fact reached sharpening Nirvana. And they can’t wait to tell you about it, and why your way is silly. Nevertheless, I think I finally have some advice regarding plane blade camber that I am not afraid to share publicly. After trying a lot of things for quite a few years I think I have a way that works well and is pretty easy as well. So here goes…
What is a “cambered” blade?
This is nothing more than sharpening the cutting edge with a bit of a curve in it instead of straight across. Nothing more. There is a reason people like to talk about it though. The amount of camber you put on a blade makes a huge difference in the way the blade performs. Though it is not rocket science, it really does matter how much camber you put on various plane irons. And to make it more interesting, the amount of camber you need varies depending on the depth of cut you plan to use.
The “right amount” of camber
For me, the real questions start with how much camber is the right amount? Here is where years of trial and error come into play and what I hope to contribute with this article. So here is the secret formula as far as I am concerned.
The “right” amount of camber should produce a shaving that is 90-98% as wide as the blade and it should feather to nothing at both edges.
This means that the correct amount of camber is directly related to the depth of cut you plan to make. This is why I do not even try to set up one plane to do everything. While this is possible and if you only have one plane it is necessary. If you have several planes set them up and use them to their best advantage. I sharpen each iron according to how I plan to use it. Scrub, Jack, Smoothing, Jointing all have different cambers. Look at the picture of the transitional plane above and you will see I am not taking a full width cut. That is because it is not cutting at full depth in that picture. A properly cambered blade should produce near full width shavings when you are working at the desired depth. The number 6 plane pictured above is perfect for final smoothing and flattening on a panel. It is cutting almost full width while set for a very fine shaving.
How to achieve the perfect camber
I have 5 or 6 planes that I use a lot. Each one of them has a slightly different blade profile. So if you are just pulling your plane out of the box. I would recommend just honing the edge and using it until you get a feel for the kind of use you are going demand from it. If you find for example that you are almost always using the plane set for a very fine cut then you need very little camber on that plane.
My “system” and I use that phrase very loosely here, is a matter of adding camber to the iron until it performs at it’s best when it is set to the depth you prefer to use with that plane. So start flat or nearly flat and add camber with each sharpening until you reach what you feel is the optimum balance of width of cut and depth of cut with a smooth reduction of shaving thickness toward each edge of the blade. On a very fine cut it should look like the picture above with the shaving turning from solid in the center to lace at the edges.
Since there are an infinite number of opinions on this I am just going to tell you how I do this and you can adopt or discard anything you like. I do not really like orienting the stone lengthwise away from my body though many do. I prefer to orient the stones perpendicular to my body. This is done for basically two reasons.
- I sharpen in a figure 8 pattern, I find this honing pattern works well when trying to hone a smooth camber on a blade.
- Some of my plane irons are wider than some of my stones. So I have to work perpendicular to the stone in these cases. Since I rely a lot on muscle memory I like to keep my motions consistent. So I work that way on all my stones, even when I do not have to.
To add camber using the figure 8 sharpening pattern you just alternate pressure from the left corner to the right corner while keeping the elbow of your back hand anchored at your waist. For me that means my left hand is applying downward pressure just behind the cutting edge. With a finger just above each corner of the blade. My right hand is responsible for maintaining the honing angle so that elbow is locked at my side.
On blades with a lot of camber like a jack or a scrub plane profile. Your anchor hand need to remain at a fixed height. So keep your elbow anchored. However, you will need to turn a bit at the wrist to allow the blade to follow the arch smoothly.
The last thing I would say is important is to use a lower bench, mine is 30″ high. That gives more control and allows you to rock your entire body back and forth without altering the angle of the blade relative to the stone.
Eat the meat spit out the bones!