Sharpening the saw chain is not more difficult than other cutting tool sharpening, but only if you have a set of special tools for sharpening it. Its tooth has a complex geometry. Chain element has two cutting edges – the upper edge and the side one. The second of which is chamfered at a predetermined angle to the line of motion of the chain, making this operation a bit trickier.
Tooth chain cuts wood like a shaving plane, and the chip thickness is defined by the height of depth gauge.
Intensive work with a saw leads to rapid dulling of chain. Within one day, it may require several sharpening procedures. The tooth quickly dulls when it meets the ground, which makes the situation worse. Touch the ground once or twice with the bar, and work should be stopped – chips become shallow, and saw doesn’t go into a wood any more. See pictures below to learn the difference between states of the tooth.
Chainsaw tooth after a collision with a ground and a stone in it
The earlier dulled teeth is sharpened the less material needed to be removed for sharpening. As a consequence – the life of the chain becomes longer. It is simple enough to find out if the chain requires sharpening. A significant criterion is the pressure you apply to work. Properly sharpened chain is pulled into the cut even with a little effort. If a chainsaw work requires increasing pressure, the teeth are dull. Dull chain can also be easily recognized if you see fine sawdust instead of big and thick chips.
In this situation, the chainsaw must be sharpened immediately. Do not to cut with a dull or faulty saw chain or you’ll get a strong tension in the body, a large cyclic loading, and poor cutting results as a consequence. Furthermore, this leads to poor performance, higher fuel consumption and increased wear on all the chainsaw gears.
Overall cutting link description
The cutting chain link consists of a basic toots body (1), top plate (2), the depth gauge (3). Tooth blade has a vertically oriented side plate cutting edge (4) and an angled back top plate cutting edge (5) that is oriented horizontally.
Upper rear angle
For optimal cutting properties, tooth blades have certain angles. The upper side of tooth blade is angled back by the upper rear angle of the blade. This angle is needed to make upper blade plunging into the wood.
Top plate cutting angle and side plate cutting angle
The angle formed by the front surface of the top plate cutting edge and the top plate of a teeth form a side plate angle and a top plate cutting angle. These angles of the various types of saws chains differ. It varies depending on the type of a chain you have.
Side plate (1) and top plate (2) cutting angles
The filing angle is measured between the top of the cutting edge and a line perpendicular to the guide rail.
The filing anlge
The filing angle can be changed, depending on the application. General rule: the larger the filing angle, the higher cutting performance when cutting not frost and soft wood.
Reducing the sharpening angle for cutting the frozen and/or hard wood makes saw run smoother and reduce vibration.
However, you should avoid sharpening angle greater than 35° and less than 25° (with the exception of the chains designed for cutting along the fibers, in which this angle is 10°).
Side plate angle, top plate angle and filing angles change when sharpening. These angles have a decisive influence on the cutting ability of the chain. Be sure to follow the recommended values.
Each cutting link has a depth gauge, that defines the amount of wood, shaved by the saw tooth per stroke.
The distance of the depth gauge determines the depth of insertion of the top plate edge into the wood (chip thickness) and, thus, productivity. Distance of the depth gauge is set depending on the chain pitch and the kind of chain. Normally it should be 0.5-0.8 mm, usually 0.6 mm. The chain link usually has a number stamped on the side of depth gauge which indicates the correct depth. High values will lead to an increased probability of chainsaw kickback, too high vibration and chain capture. Lower values lead to a drop in performance. Since the depth decreases with each sharpening due to reduce the upper side length of a tooth, the depth gauge also requires periodic shortening – every 5-10 time you sharpening the chain.
- You have to find out the pitch (size of a chainsaw link). There are a several types of chains, which have different pitches. You can take a look on a chain link to find a code digit. It is located on the outer side of depth gauge. See figure below:
- These numbers are referred to actual pitches of chains. According to it, select the proper round file from the table below. You can only use this specific file for sharpening your chainsaw, or your chain will be spoiled and unable to restore.
Table for selecting the file
- Diligently clean your chain. You can use hard brush to remove dirt, sawdust and debris. Use conventional store bought detergents or mineral spirits to get rid of oils. Do not purchase too aggressive cleaners, because some of them can harm the plastic housing of your saw.
- Examine the chain for damaged or excessively worn links and teeth. If you find a tooth that is chipped, broken or bent, replace it with a new one. Broken links are dangerous to use. The upper plate (the upper side surface of the cutting teeth) should be at least 1/4 inch long. Shorter upper plate is overly worn and can break during the saw motion.
- Fasten the saw and its bar. This will ensure you a safe and accurate sharpening. It is best to hold the blade in a vise so that the chain could rotate freely.
Correctly fasten chainsaw
- Keep the file with both hands. One on the handle, and the other to direct it accurately. While sharpening, hold the file horizontally (assuming that the chain is oriented horizontally). The angle between the file and the bar (when you look at it from above) must me 25° or 30° (read the saw specification). Keep the file 1/4 of its diameter above the top plate. And note that you only sharpen the tooth on forward movement. Don’t touch the teeth when you move the file back. You have two main aims: first to make all the cutters the same in height (so every link will cut the same amount of wood with each stroke and every tooth will wear equally) and second is to make all the teeth match the angle they were machined at the factory. You can sign the tooth you started with using a felt tip marker.Filing direction Filing angle Horizontal position
- Regularly rotate the file at a little angle, to make its wear equal everywhere. We recommend to move the chain during the work, so the link, you are sharpening is always near the tip of the bar. Remove the metal filings while sharpening.
- To check the quality of sharpening, carefully inspect the cutting edge. Its surface should be equally bright.Not bright enough
Uniformly bright tooth.