Hair shears, like scissors, are made of to two knives joined together. Each knife has a cutting blade. The blades have three sides: the flat inside blade, the cutting edge and the outside angled blade (this is what you sharpen).
But know that hair shears are fine instruments. They are not just any old pair of scissors. Sharpening the blades is something of an art, so you shouldn't try it if you are a novice. You should get a professional to sharpen your shears because the wrong technique could ruin them. However, if you must, this is the basic technique to sharpen hair shears
Place your cloth on a firm, non-slippery surface. You want to be sure that the shears will not move around as you're sharpening.
Open the shears to their fullest extent, and turn the shears so that the open knives are facing up.
Hold one inverted handle comfortably in your left hand while bracing the other handle on the cloth. In essence, you are holding the knife you will sharpen and using the other knife for stability.
With your right hand, grab the whetstone as if you were holding a fat tennis racket handle.
Place the whetstone on the outside blade, tilting it to match the angle of the outside blade. This a very critical point, and doing it incorrectly can damage your shears.
The whetstone should be at a 45- to 90-degree angle to the knives you are holding in front of you.
Stroke the whetstone repeatedly from the back of the blade to the tip. Don't use too much pressure; let the whetstone do the work. The strokes should be full and even. Don't let the whetstone drag back and forth or move in a circular motion.
Count the number of stokes for reference when sharpening the other knife. It is important to get an even sharpness between the knives.
Check the sharpness by rubbing your fingers on the inside blade. Never touch the whetstone to the inside blade because it will create gaps at the point of cutting (where the two blades come together during the cutting stroke).
The blade is sharpened when you feel a consistent burr along the inside blade. If the burr is not even or is non-existent, continue stroking.
Reverse the shears, holding the other handle, and repeat steps 4 through 8.
When you are satisfied with the sharpness of your shears, hold them open in the normal cutting position and make one quick cutting motion. This will remove the burr from the inside blades. This step, however, is only valid if your shears are in good condition and have not been damaged by drops. Otherwise, snapping them shut may create nicks in the cutting edge.
An alternative to snapping the knives shut is to close them by pressing the tips together slowly while slightly forcing the blades away from each other. Then squeeze the blades together while opening them. This, too, will remove the burr.
Sharpening shears must be done with care, skill and patience. If you are new to this, try practicing on a pair of fabric scissors until you are comfortable with the process.
There are three reasons why having your shears professionally sharpened is preferable: 1. Hair shears are not the same as scissors. The outside blade is often bevelled and sharpening it correctly is very difficult. You could damage your hair shears. 2. Professional hair shears are made of a hard metal that is harder to sharpen than the metal of regular fabric scissors. 3. Professional hair shears are very expensive; ruining them would be more expensive than having them sharpened professionally. Always store your shears in their own container. Don't store them with other things that might damage them. Only cut hair with your shears, using them for other purposes will damage the blades. This also means keeping them out of sight of others who might use them like just any pair of scissors. Never touch the cutting edge with the whetstone. Never sharpen the inside blade. Don't drop your shears, as that can do a lot of damage.