The European manufacturer Stihl offers more than 60 hedge trimmers in its range. Most of the devices use a battery as a power source.
However, the range also includes models with a gasoline engine. The type of power supply is secondary in this context. All models require regular care.
In addition to cleaning after use and lubrication, this includes sharpening the blade.
How can you tell that it’s time to sharpen the knife?
There are several signs. Among the most common is that the cutting performance of the battery garden shears or gasoline hedge trimmers noticeably decreases.
Cutting the branches requires more effort. The motor runs hot and the hedge trimmer gets stuck more often.
The clearest sign that the blade needs sharpening on the respective device is the condition of the cutting surfaces. On a sharp blade they are smooth, on a dull blade they are frayed.
Sharpening a cutting knife in 5 steps
Before you start sharpening the device, first lay out the necessary tools. You will need:
- Flat file
- Sharpening stone
- Cleaning cloth
- Grinding water
- Wear safety clothing when working. You will need gloves and safety goggles.
Before you start working, make sure that the motor cannot start suddenly. To prevent this, remove the batteries or unplug the power cord in the case of an electric hedge trimmer. If the hedge trimmer has a gasoline engine, remove the spark plugs.
Place the hedge trimmer or the cutting blade on a flat and stable surface (workbench, garden table) and make sure that it cannot slip.
Before you start sharpening, the blade must be cleaned. To do this, spray the cutting surfaces with a cleaning agent that dissolves resin and dried plant sap. Let the detergent soak in for a while before wiping it off with a rag.
sharpening with the flat file
Each cutting tooth is sharpened individually. In order for the knife to be sharpened evenly along its entire length, the same number of file strokes must be made for each cutting tooth.
The flat file must be applied at a certain angle. You can find its value in the instruction manual.
Apply the file only in the forward stroke. When pulling it back, it must be lifted so that the cutting edge does not become blunt again!
Do not remove too much material when sharpening. The wear limit is 5 mm. If it is reached, original knives must be ordered for the equipment.
When sharpening, a burr is formed on the underside of the cutting tooth. Remove this burr with the whetstone.
To do this, turn the cutter over so that the underside is facing upwards. Take the whetstone and pull it with a careful wiping motion to the tip of the incisor.
The last step is to clean and maintain the cutting blade so that the blade does not rust. First, carefully wipe off the grinding dust. Then spray or brush the blade with a care product.
The preparation dissolves resin and plant sap residues and coats the blade with a thin layer of oil. This reduces friction so that the hedge trimmer works more easily. At the same time, the thin film protects the blade from corrosion.
How often should the cutting blade be sharpened?
There are no fixed specifications or intervals specified by Stihl for this. The manufacturer recommends sharpening the blade after every 50 hours of operation.
How often you need to sharpen the blade depends on how often you use the hedge trimmer and what you trim with it. If you trim a lot of hedges and/or have to cut thick branches more often, the blade will become dull more quickly.
In practice, it has been shown that it is better not to wait until the above-mentioned signs of a dull blade appear, but to take action beforehand.
At least before the start of the gardening season, you should thoroughly clean the hedge trimmer and take the opportunity to lubricate it and sharpen the blade.