Three angles are important when sharpening a planer knife

The right angle when sharpening a planer knife arises from the balancing of optimal action on the planing material with the least possible setback. The angle also determines the required contact force. The general angular position of the planer blade is supplemented by special chamfered bevel angles.

Cutting angle is crucial

The basic angle with which a planer knife hits the planing material is determined by its position in the planer. This wedge angle is normally 25 to thirty degrees. This results in the common types of cut a cutting angle between forty and 45 degrees.

Special planing tasks require higher angles when grinding. For example, the tearing of wood during planing against the grain can be reduced by increasing the angle. With each increase, however, a higher effort is required. The highest cutting angles for grooving and cleaning are up to fifty degrees.

Blade tip and chamfers

The construction of the blade tip or edge is not symmetrical. It consists of a chamfer and a mirror for most types of planing knives. The chamfer is the beveled side of the blade, the mirror side forms the smooth counterpart.

The planer blade is sharpened at the chamfer and provided with an angle to the front edge. This corresponds to the wedge angle of 25 to thirty degrees. When inserting the planer knife with the chamfer facing down to the planing material, this angle "propagates" on an imaginary impingement line. The chamfer and its angle correspond, so to speak, to the "cutout" of the blade, which it needs in order to be able to move freely over the planing surface. Therefore, experts also speak of the clearance angle.

If the planer knife is placed in reverse in the planer, the smooth mirror side is facing down to the planing material. In this case, the angle of the sharpened chamfer is ineffective, since the wedge and cutting angles are only affected by the position of the planer blade as a whole.

Tips & Tricks

You will find a special feature on planing knives, in which two chamfers are ground. A flatter main angle is sharpened steeper on the last course piece to the blade through a kink. Angle combinations of 35 to 40 degrees are possible here around the degree of enlargement of the angle after the kink. The chip removal of the planing material changes and you can create more suitable wedge and cutting angles for special planing tasks.

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