A rasp file is a type of file designed to be used on wood. It has coarse teeth punched out of steel. They are meant to be used after a rough cut of the saw and before the final smoothing of sandpaper.
Step 1 – Choose the Right Rasp
Rasps can come in numerous combinations of coarseness, shape and teeth patterns. A flat rasp has large coarse teeth to remove material quickly. A combination rasp and file has 2 files and 2 rasps. You will also find that rasps come in a range of coarseness. The coarsest to finest are the wood, the cabinet and the bastard. Files come in lengths starting at 4 inches and then increase by 2-inch increments. In general, a longer length has larger teeth. Most rasps are machine made by driving a punch into metal that has been heated.
A machine-made rasp has teeth in rows one behind the other. This means the rasps will cut grooves and not leave the surface smooth. A finer rasp has teeth that alternate position from row to row makes a smoother surface. These are known as Patternmaker’s rasps. A “four in hand” rasp has a file and rasp on both the flat and round sides. This gives 4 useful cutting tools in one. A type of rasp called a riffler has a rasp on each end and is used for carving wood and detailed furniture making.
Step 2 – Choose a Handle
Rasps don’t always come with a handle. If you need to add a handle you have a few options. A universal handle can fit different shapes of rasps. You can also buy a handle for each shape you buy. Try a new ergonomic handles that are more comfortable to grip. To put the handle on a rasp, hold the handle in one hand and push the handle’s end onto the rasp. Put your hand holding the rasp pointing upward and forcefully bring the handle’s end down on a hard surface. Forcing the handle onto the rasp can shatter the steel.
Step 3 – Use the Rasp Safely
You will need both hands to use a rasp. Take the point between the thumb and first two fingers and then clasp the handle with your other hand. Don’t saw back and forth because a rasp only cuts in one direction. Dragging the rasp back over the surface will dull the rasp and give you a rougher finish. Instead, push the rasp into the wood and then lift it off at the end of the stroke. Repeat this action of pushing and lifting.
Step 4 - Storage
Because rasp teeth are delicate and need to be protected, don’t just throw it in your toolbox with the other tools. You should either use the protective cover it came with or wrap it in a cloth before putting it away. This will keep it sharp and extend the life of your rasp.