The lawn mower is a popular friend and helper for every hobby gardener. As long as it works reliably, it makes cutting the lawn a lot easier. Only when the lawn mower blade is blunt do numerous users face enormous problems. Does the nut have a right-hand thread or a left-hand thread? And how can the knife be changed easily and at the same time safely?

Direction of rotation and screw

Once you have realized that the lawn mower blade is blunt, it is time to change it. Because sharpening when installed is normally not possible. The first concern is loosening the bolt or nut that holds the knife in place. It would be nice if a general statement could be made here as to the direction in which the safety catch of the knife can be opened. But unfortunately that is not possible. Because whether it is a right-hand thread or a left-hand thread depends on one crucial thing:

  • the direction of rotation of the blade

The rotation can be recognized very easily by the following things:

  • Marking on the lawn mower blade, eg arrow
  • Cutting the knife: always in the direction of rotation in front
  • Soiling: Cutting edges mostly blank, backs with deposits of pieces of grass, dust and dirt
Tip: The marking of the rotation on the knife is often no longer clearly recognizable or has even disappeared completely. A damp cloth and possibly a spatula will help to remove the crust of grass and dirt and make the marking visible again!

Once the direction of rotation of the knife is known, it is very easy to determine in which direction the nut must be loosened. Here it is important to know that the screw is always set up in such a way that it tightens when the lawn mower blade rotates. This is for safety and prevents unintentional loosening during operation and thus clearly the danger of a knife flying around in an uncontrolled manner. For the direction this now means:

  • Right -hand rotating blade (cutting on the right side of the blade when looking at the mower from below): right-hand thread, opening direction to the left
  • Left-hand rotating blade (cutting on the left of the blade when looking at the mower from below): Left-hand thread, opening direction therefore to the right

Change correctly – helpful tips

Once the opening direction of the nut has been determined, nothing stands in the way of changing the blade. However, you should pay attention to a few essential things in order to keep the sometimes considerable risk of injury from working with the knife as low as possible:

  1. Prevent ignition: Like any other engine, the lawnmower’s can also be pushed easily. This can happen unintentionally if the nut is subjected to high force and suddenly loosens. Therefore, before you handle the knife for the first time, you should definitely remove the spark plug connector to prevent the engine from starting.
  2. Secure knife: The compression of the cylinder offers some resistance to the wrench. However, if this is overcome with a tight screw connection, the lawnmower blade spins and can cause serious injuries despite the blunt blade. Therefore, the knife must be secured against unintentional movements. Alternatively, it can be wrapped with a rag and held by hand as an abutment for the key.
Tip: The screw connection on the blade is often very tight due to the heat generated when mowing and the dirt. Putting a few drops of penetrating oil on the threaded head before applying the wrench helps opening and makes work easier.

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