The sharpening angle of the planer knife serves as one of the most basic characteristics of the blade; this determines the ability to cut and the period during which the blade will remain sharp. If you reduce the sharpening angle, the cutting qualities of the tool will be increased, while the strength characteristics of the blade will be reduced, which is especially true for shocks and interaction with hard objects. For this reason, different sharpening angles are defined for different tools, while more solid materials that can be machined should have a more impressive sharpening angle.
Features of the work
Planer knives in factory conditions are sharpened at the most appropriate angle, but when it becomes necessary to sharpen a tool that has lost its sharpness, it is required to preserve the existing features of sharpening. If you carry out the work without the use of appropriate devices, then you have to pay special attention to the correct position of the surface to be sharpened when exposed to abrasive. But if there is a need to change the angle of sharpening, here will have to use special tools.
Their description will be presented below, and they are intended for carrying out manual sharpening not by chance, as the sharpeners working by electricity do not allow to achieve high results. Large revolutions of the abrasive surface cause the processed blade after the next sharpening becomes soft and dull in a shorter time. A number of specialists have not used electric sharpening tools when sharpening a tool with their own hands.Back to table of contents
The desired angle of sharpening will turn out if you install the knife blade in a vertical position, while you have to move it along the bar fixed at a certain angle. Carrying out such work will be easier than when the grinding surface is horizontal.
The bar in a given position can be strengthened with screws, placed between two triangles of wood.
The correct sharpening of a planer knife with a bar: a - the position of the knife when sharpening; b - the position of the chamfer; in - removal of the agnail.
Before you sharpen the knife, you should accurately set the angle using the rules of trigonometry. Thus, for a cutting surface whose angle is 30 °, the angle can be determined using the following formula: x = 30 ° / 2 = 15 °; angle y = 90-x = 90 ° -15 ° = 75 °; the ratio b / a = tg (y) = tg (75 °) = 3.732 (it is permissible to calculate by means of a calculator set in the mode of engineering calculations); then if b = 15 cm, a = 15 / 3.732 = 4.0 cm.
Alternatively, the sharpening bar can be fixed in a socket that is able to orient it in the desired position. The disadvantage of this option is the impossibility of a smooth adjustment of the angle of the bar.
The planer knife can be positioned both horizontally and vertically, which is easier compared to fastening the grinding bar in a horizontal position and holding the surface to be ground at the right angle. In this case, it will be necessary to lay the object under the bar as a piece of wood with the desired angle.
In order to sharpen the knives, you can prepare another installation, the surface to be sharpened in it should be strengthened, while the bar will move at a certain angle by means of a guide to which it is fixed.
Correction of the cutting edge of the knife: a - validation; b - elimination of skew.
For work on the manufacture of tools will need to use:
- threaded bar M8;
- washers in the amount of two pieces;
- nuts that hold the bar tightly.
The wooden element must have a length of 200 mm. The heat shrink tubing should cover the threads. You will need to work and stationery clips, which will strengthen the stand guide at the desired height, their task is also to ensure a smooth adjustment of the angle of sharpening. In the role of the base will be a bar of 40 mm, which in the process of sharpening the knife should be in the hand.Back to table of contents
The simplest device is the installation, which has a bar at the base, on the top of it there is a sharpened knife. Correction of the angle is permissible to make the position of the bar relative to the base of the abrasive and the step from the blade to the point of fixation. If you need to sharpen a knife on the one hand, the device should rest with the blade on the abrasive, but on the other - on the corner of the bar. In order to ensure a better sliding of the wooden element along the base and to protect the working area from scratches, something must be put under the wooden bar, for example, glass.
Cutting edge correction: rounding ends.
If you decide to install in the plane just sharpened knives, then it should be noted that such a device has one drawback, which is to use only a certain area of abrasive. To eliminate this drawback, it will be necessary to supplement the device somewhat.
The installation is represented by a steel bracket, in the inner space of which a shelf is fixed. A mounting screw provided with a heel implies fixation of the tool to be sharpened. Rollers should be mounted on the axle, whereas on them should be mounted workpieces made of a conventional hose. In the process of sharpening the blade, the installation with the tool clamped in it rolls over the abrasive surface, but here a part of the length of the abrasive is not used.
The plane after the completion of the work must be equipped with a knife with an angle of approximately 30 °.
It is almost exactly possible to make sharpening without measuring, it is important to achieve the right balance between the width of the chamfer and the thickness of the surface to be treated. When chamfer, the width of which is 1.5 times the thickness of the surface to be machined, the taper angle is approximately 28-30 °.
In the process of sharpening, the straightness of the blade can be analyzed using a perfectly straight surface. The blade should have a chamfer of the same width along the entire length. It is necessary to continue the work on sharpening until the blade has the thinnest barbs, which should be almost invisible, whereas the chamfer should not have even the smallest bulges or concavities.
Such work can be done independently or entrust the work to professionals.