A correctly sharped chain reduces costs and improves productivity. Stihl guides us on chainsaw sharpening best practice.
The first step is to select the diameter of the round file to suit the chain pitch. This is done by checking the code digit for the chain pitch on the outboard side of the depth gauge. The manufacturer’s specifications should be consulted to determine the chain pitch. Proper chainsaw sharpening files should be used.
The following steps should then be taken regarding holding the file:
- Hold the file handle firmly with one hand and guide the file with the other hand across the cutter on the forward stroke.
- Start with the master cutter and position the file so that you can apply pressure and file from the inside to the outside of the cutter.
- Always hold the file at a right angle (90°) to the guide bar.
- The file only sharpens on the forward stroke – lift the file off the cutter on the backstroke.
- Rotate the file a little at regular intervals while filing to avoid one-sided wear.
- STIHL saw chains are generally filed to an angle of 30° – parallel to the service mark for the filing angle.
- Hold the file so that one quarter of its diameter projects above the top plate.
If you can see dark areas on the cutting edge, the cutter is not yet sharp. The cutting edge is properly sharpened when it is uniformly bright. Then file all the cutters in that row to the same length, then turn the chainsaw 180° and file all the cutters in the other row. All cutters must be the same length as the master cutter.
To lower the depth gauge, simply place the filing gauge on the saw chain. If the depth gauge is higher than the filing gauge, if must be lowered. File down the depth gauge until it is level with the filing gauge. On saw chains with humped drive links the hump is lowered along with the depth gauge. File the top of the depth gauge parallel to the service mark – but do not lower the highest point of the depth gauge in this process. Take care not to touch the freshly sharpened cutter with the flat file.
Additional tips provided by Stihl are as follows:
- Before you start sharpening, mark one cutter with a felt tip pen. After two or three strokes of the file, check how much material has been removed. If the surface looks uniform, your filing action is correct. If there are still patches of color in places, check that you are using the right file and make sure you are not holding the file too high or too low.
- The depth gauge setting may be increased by up to 0.2 mm for cutting soft wood in mild weather conditions – no frost. The filing gauge for the next chain pitch up may be used for this purpose.
- Never continue working with the chain until it is completely dull. A few strokes of the file at regular intervals quickly restores full sharpness.
- Count the number of file strokes and use the same number on each cutter to obtain cutters of identical length.
- If you find that the cutters in one row are shorter than those in the other row, you have used more pressure while filing the row concerned. Correct the length of the cutters by performing one or two strokes of the file on the longer cutters
Source: http://www.stihl.com/saegeketten-schaerfen-kette-schaerfen.aspx