Many pocket and two-handled dry wall rasps have blades that can be replaced when the teeth become dull and worn.
It is far quicker to replace a worn blade than sharpen the teeth with a file. Also, as blades are inexpensive, when you take into account the time required to sharpen a blade it often works out cheaper to replace it.
Step 1 – Loosen screw
Turn the screw anti-clockwise to remove the tension on the blade. Models that do not have a thumb screw will require the use of a screwdriver to do this.
The blade of a pocket rasp is held in place by two hooks – one hooks around the front of the rasp’s body and the second locates into a hook attached to the screw in the rasp’s body.
As the screw is turned anti-clockwise (as viewed looking at the head of the screw) the hook within the rasp’s body is pushed forwards. This removes the tension that holds the blade in place on the rasp, allowing it to be unhooked.
Step 2 – Remove and replace blade
Detach and remove the worn blade, first by unhooking it from the hook attached to the screw, then from the front of the rasp’s body.
To fit the new blade, first hook it onto the front of the rasp’s body then attach it to the hook connected to the screw.
Step 3 – Tighten screw
Turn the screw in a clockwise direction (as viewed looking at the screw’s head) to apply tension to the blade in order to secure it to the dry wall rasp.
How does the screw apply tension to the blade?
When the screw is turned, a small metal plate within the dry wall rasp is moved along the screw’s thread. The small plate hooks under one end of the dry wall rasp’s blade, so when the screw is turned clockwise, the distance between the far end of the rasp where one end of the blade is attached and the plate where the other end of the blade is attached increases.
This increase in distance applies tension to the blade and holds it in place on the rasp. When the screw is turned anti-clockwise, the distance is decreased, which removes tension from the blade, allowing it to be removed from the rasp.