beyond sharpening----cambering

[Ken S]

I do not recall the sources, however, I remember watching more than one youtube where a plane blade was sharpened. At the end, to show off the sharp blade, the plane took a long, thick shaving. I am not doubting the sharpness of the blade, but, the plane and operator looked like they were working harder than they should be with a sharp blade.

I suspect the problem was a combination of incorrect camber and a blade set for too thick of a shaving. A correctly set and cambered blade acts as a depth stop with the bed of the plane.When a plane is set up as the final smoothing plane, the shaving is only about .001" or .025mm thick. When properly set, the camber fades off to nothing at the edges of the blade. Since the highest part of the arc only extends .001" from the bed of the plane, the thickness of the shaving is limited to .001".

A jointer or trying plane, used before the smooth plane to flatted a surface, usually takes a deeper cut, generally around .005" or .125mm. This blade is ground with more arc, such that the top of the car extends the same .005". Again, the camber limits the depth of the cut. If this depth of cut is tiring, one can easily make the camber slightly less. The process will then involve more, less tiring passes.

There are differences of opinion with edge jointing. One tradition says the edges should be dead flat. The other tradition prefers cambered edges so that when the glue joint is clamped, the edges are compressed and less likely to show gaps. Each school has its followers. Power tool users who joint with a power jointer generally prefer flat edges.

When working with rough lumber or when a lot of wood is to be removed, a jack or fore plane is normally used first. These planes have much more camber, often 1/32" (.030" or .8mm) or more, depending on the species of wood. David Charlesworth has made the comment that most small shops rarely have to remove more than a few thousandths of an inch. That would partially explain why he is so comfortable with his "super smoother" (number 5 1/2 plane, a very large jack plane set up as a smoother). The 5 1/2 is the closest modern plane to the traditional English panel plane so popular with earlier craftsmen.

A sharper who does not understand cambering is only half equipped to sharpen bench planes. Any of the Tormek Square Edge jigs can produce any of these amounts of camber. The new SE-77 makes the amount of camber more automated and makes uniformity easier.

Ken