Circular saw is a necessary tool for the construction of wooden buildings or for frequent work with wood. During operation, the cutting tool wears out. Sharpening circular saws, carried out correctly, will return the second life to the machine. With all the seeming simplicity of the design, circular saws have no worthy rivals in the longitudinal sawing of wood. In the manufacture of many wooden profiles (for example, timber) is very important accuracy in size.
Circular saw design.
Timely sharpening of circular saws ensures high performance of the main cutting element of the saw.
The main parameters of the saw
Circular saw refers to cutting tools in the form of a flat disk, on the outer edge of which cutting teeth are placed. The main purpose is straight and precise sawing of wood in the longitudinal direction.
All circular saws consist of a disk (blade) and soldered plates, which are cutting elements. The disc is usually made of steel grades 9HF, 65G, 50HFA and some others. Tungsten-cobalt alloys are used for the teeth.
Saws differ in a form and type of sharpening of the cutting elements. The main parameters include:
- external diameter;
- number of teeth;
- slot width;
- disk thickness;
- diameter of the inner hole for mounting on the drive shaft.
Circular saw blade inspection scheme.
The cutting element of the circular saw has four working planes, which can be divided into two main (front and rear) and two auxiliary (side). These surfaces, intersecting with each other, create cutting edges, divided into the main (top) and two auxiliary (side) edges.
In different types of saws, the cutting teeth differ in shape. Straight is used for fast sawing with low quality cut. Oblique is with the left or right tilt of the back surface. On the saw, the teeth of different inclination alternate and are called alternately beveled. This design of the cutting elements is used most often.
The next form is a trapezoid tooth. Most often, the cutting elements of this form alternate with straight teeth. The bevels on the edges are made at an angle of 45 ° on both sides. Conical teeth are used as auxiliary. Their side surfaces are rounded, and the front face is usually flat.
One of the most important characteristics are the angles of sharpening. It is customary to distinguish four basic angles of sharpening: the front and rear corners, as well as the angles of the front and rear planes. The magnitude of the sharpening angles is determined by the purpose of the saw. As a rule, the circular saw has a significant rake angle (15-25 °). In the case of universal (longitudinal-transverse) saws, an angle of 15 ° is established.Back to table of contents
The need to sharpen saws
Sharpening circular saw.
During operation, the cutting edges of the teeth wear out. The main (upper) edge is exposed to the greatest wear. When worn to 0.1-0.3 mm, the cutting edge cannot fully and qualitatively perform its function. The front plane is subject to considerable wear. If the operation of the saw was carried out very actively, then the side planes (edges) are also damaged.
Increased wear of the cutting elements leads to a decrease in productivity, cutting accuracy (a straight line can turn into a wavy line). In addition, the untimely sharpening leads to the complication of the entire operation. It is necessary to begin work if the chamfering reaches 0.2 mm.
A characteristic sign of blunting the saw is overheating of the teeth and the entire disk during operation. Excessive overheating of the cutting elements manifests itself in the form of their blackening. During sawing, the smell of burning is becoming more pronounced. It must be remembered that the operation of a worn-out saw causes an overload of the engine. This can lead to its failure.Back to table of contents
Features sharpening saws
The main task of sharpening the saw - sharpening the cutting edge. However, simultaneously with the solution of the main task, additional operations should be carried out: sharpening the front and rear planes, grinding the tooth, restoring the shape of the tooth and all the main angles.
Saw tooth scheme. Planes: a- front, b - back, in - two side. Edges for cutting metal: 1 - main, 2, 3 - additional.
All saw teeth should be sharpened equally. It is recommended to complete the work on the rear plane. Metal removal from planes is usually made to a depth of up to 0.15 mm.
Begin by checking the basic parameters of the teeth. Before sharpening, it is necessary to thoroughly clean the saw from dirt and tar, as well as to degrease the surface. Work is best done using abrasive wheels and the necessary fixtures.
The processing of the anterior plane of the tooth includes certain rules. The saw is fixed horizontally. The emery circle is applied to the front plane of the tooth. The first item to be processed is marked. Carefully handled plane. Then the specified rake angle is formed and sharpened. Moving in a circle, all the teeth are sharpened.
Sharpening an oblique tooth is different in that the saw is installed with an inclination angle equal to the inclination angle of the front plane. It is recommended to set the angle of inclination using a standard protractor. Work begins with the installation of a positive angle. Gradually moving in a circle, every second cutter is sharpened. Then the angle is reversed, the remaining teeth are sharpened.
When machining the rear plane, the saw is fixed so that its rear plane is in the same plane as the emery wheel. The operation itself is carried out similarly to sharpening the front plane.Back to table of contents
Sharpening angle chart.
Sharpening is best done using an emery wheel. For sharpening the teeth of a circular saw, you can use circles from modern abrasives or diamond wheels. During operation, the emery wheels are recommended to be cooled with a special liquid. Circles are selected with the highest grain. The speed of the emery wheel when processing the saw should be 1300-2500 rpm.
The saw fixing system may be different. In practice, there are options when the saw is attached, and the circle moves and bends at the right angle. The emery wheel can be fixed, and the saw blade moves and bends. A saw is usually attached, but with the possibility of changing the angle relative to the surface of the circle. In simple designs, all operations are performed manually, including control over the amount of metal removed. In devices it is recommended to provide a limiter for the circle to enter the space between the teeth.Back to table of contents
Making a simple sharpening device
The simplest device that can orient the saw in a given direction can be made as an adjustable platform. The base is made in the form of a horizontal stand, located on the same level with the axis of the emery wheel. Just putting a saw disk on it, provide a perpendicular arrangement of the front and rear planes of the teeth in relation to the circle. To move the stand one of its side is fixed through the hinge, and under the other put two adjusting screws. This stand is able to fix the disk at the right angle.
For more accurate alignment of angles, the center of the disk must be strictly fixed on the surface at one point.
For sharpening circulars the following tools are needed:
The pattern of grinding metal on the teeth of the saw.
- emery circle;
- emery sandpaper;
- depth indicator;
Sharpening circular saws must be done in a timely manner, at the first signs. For sharpening it is recommended to purchase or make the necessary fixtures.