camber on handplanes

[Ken S]

If a bench plane (hand plane) with a blade ground straight across is used to plane a board wider than the blade, it will leave "plane tracks". The key word here is "wider". If the plane is only used with board surfaces narrower than the blade, a straight across grind will produce a flat surface with no plane tracks.

If the plane blade is ground with a slight arc, called convex in the handbook, also called camber, and the projection of the blade is set such that only the arc or most of it projects, the tracks left by the plane become blended and barely noticeable.

The amount of camber depends on the thickness of the shaving. A plane used for final smoothing will typically make a shaving around .001" or .025mm thick. This is far too thin to be efficient for initial rough planing. It will leave a fine finish. The camber for this cut should extend only around the thickness of the cut.

A plane used for initial preparation of the board will make a much deeper shaving, typically around 1/32" or .75mm. With a matching camber, this plane will leave noticeable scallops. These are removed in later stages with finer shavings. These planes, usually called jack or fore planes remove material quickly.

Between the jack and the smooth planes is the jointer plane. These are used for leveling and flattening boards prior to final smoothing. They are generally longer planes and make shavings around .006" or .15mm.

The amount of camber is determined by the thickness of the shaving, not the length of the plane. Occasionally one plane, typically a jack plane (approximately 14" or 350mm) can be used with multiple blades for the three functions.

Adding camber to a plane has always been possible with the Tormek. With the older square edge jigs, extra grinding pressure was exerted on the sides until the desired arc was obtained. Obtaining a smooth arc required some skill and patience, but could be accomplished. With the advent of the SE-77, the process became "jigged" with more consistent results more easily attained. Controlling the amount the left and right adjusting screws were backed out made the amount of camber controllable and repeatable.

Handplane Essentials by Christopher Schwarz is an outstanding reference.

Ken

[mark1]

Nice post Ken - thanks!