Clippers take a lot of abuse when cutting objects. Several kinds of clippers exist, each designed and intended for a specified use. Clippers are generally made to last and usually are cheap. If they become dull, rusty or broken, it is easy to replace them with new blades. An occasional blade sharpening care can help extend their usable life even longer. Blade oiling is not required but will prolong the period between sharpening sessions.
Electric Hair Clipper
Remove the two Phillips screws securing the blade; note there are models having three or four screws. Upon loosening the blade, take it out of its seat. Brush away any hair, skin cells and other debris off the blade. Dip a soft clean cloth in rubbing alcohol, then wipe it over the blade. Rub the blade against a knife sharpening stone when dried from alcohol. Drip some blade oil on the blade made only for hair trimmers. Attach the blade into the clipper assembly.
Toenail and Fingernail Clipper
Close the blades so they are touching each other before sharpening. With the blades in the closed position, take a fine round file and rub it against the dull blades of the clipper. Try to keep the stroke speed long and even.
Aluminium foil also can be used to sharpen the clipper blades. Take some foil and flatten it into a flat sheet. Position the foil sheet between the two clipping blades. Close the blades so they are squeezing the piece of aluminium. With your fingers on the clipper, have the blades "bite" the aluminium several times by simulating the nail clipping motion.
Pet Nail Clipper
Sharpen the pet nail clipper only if needed. In many cases, the nail clippers just need to be cleaned. If the blades truly are dull, begin the sharpening process by removing the two screws holding the blades using a Phillips screwdriver. Once the blades are separated from each other, sharpen the blades one at a time with a bench grinder. Be careful not to grind the blades too much as they are delicate. For a bench grinder substitute, use a flat nail file or knife sharpening stone to rub the blades. Reassemble the clipper after sharpening.
Use oil made specifically for pet clipper blades. The most convenient ones are in spray bottles. Spray a thin lubricant layer onto the blades and let air dry. Do not dismantle the clipper if you just need to oil the blades.
Disassemble the clipper with a wrench. Place the parts in the order that you took them apart to reduce confusion when putting them back together. Remove stubborn debris such as dry mud off the blades using soap and a stiff brush. Use a rag dipped in mayonnaise or kerosene to remove sap and rust, if needed. Sand the blade using a medium-coarse flat file. Have the blade facing you, then start sanding the blade from the tip, working toward the part near the handle. Sand each blade several times using one-way motion only. When the file comes to the end of the blade, lift the file and place it at the blade's tip, then repeat. When finished sharpening, put the clipper and its blades back together. Lastly, protect the blades with a thin coat of rust blocker.