Plane Iron Rehab – Camber

My fundamental operating preference is for almost all of my hand plane irons to have camber, or some degree of curve along the cutting bevel.  About the only plane irons that are not cambered are 1) block planes, of which I have many and use nearly every day, 2) smoothing planes, 3) “miter” planes for use on shooting boards, and 4) rabbet/dado planes for crisp shoulder/joinery work.  Otherwise, pretty much everything is cambered.

And, since it such a routine part of my work, I have developed a simple, easy, and straightforward process to deal with inducing camber and sharpening cambered edges.  It has to be simple and easy or I would not go there.

Exactly how much camber depends on the use of the tool.  For general-use bench planes like jointers it’s a teensy bit (the precise technical description) and for scrub planes it is a gob of camber (again, the precise technical description), and jack planes and foreplanes somewhere in the middle.  How much camber, and when to induce it, are almost whimsical at this stage of my life after decades of creating and maintaining them.  That said, the basic process is the same in that it depends on how my hand bone is connected to my arm bone, and my arm bone connected to the shoulder bone.

The most basic truth is that the hand/arm/shoulder joints function as pendulums (pendula?) and their pivot points.  As a result, while I use a sharpening jig to establish the bevel on a new or really trashed old iron, virtually all of my sharpening at the stone is designed to overcome or counteract this pendulum imperative.  I will not go into depth here on my theory and practice of sharpening (ask three woodworkers about sharpening and you are likely to get 74 opinions), in routine sharpening I am a freehand sidewinder, and in the world of cambers this is an added benefit.

Here is how it works for me.

Holding the iron so tha the bevel is flat on the stone surface, when pushing the iron away from my body I press down hard with my thumb. On the return trip, pulling the iron back towards my body, I press down hard with my index finger. With this simple process camber is induce. Exactly how much camber depends on how many strokes you move fore and back, and how coarse the stone is.

With the iron bevel-down on the sharpening stone, I establish (or discover) the bevel angle moving the blade fore and back.  Here’s the sublime part, camber-wise — all I have to do to induce the camber is press more on the trailing edge on the push stroke and on the pull stoke to begin a rocking action and remove more material in a near perfect curve on one side for the push stroke and the other side on the pull stroke.

Simple as that.

Again, exactly how much camber and when to induce it depends on the purpose of the iron.  For bench planes I induce it at the 600-grit stage of the sharpening process. NB – my progression for a new or derelict iron edges is to work up through very coarse silicone paper or diamond stones to 220 diamond to 600 diamond to 1200 diamond/1000 water stone to 8000 water stone, followed by stropping with micro-abrasive impregnated into a wooden board.

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BTW I am playing with creating short shop-based videos, and if there is enough interest I could easily feed this topic into the pipeline.