To make sure your clipper blades give you the smooth haircut you are looking for, you have to oil the blades. Using clipper oil reduces friction and pulling at the hair in addition to helping maintain the life of the blades.
How to Oil Clippers
Oiling the blades reduces friction and keeps the clippers from pulling and snagging as you cut your hair. A drop of oil at the corners of the blade's top, as well as the foot of the blade, is all it takes.
After you apply the drops of oil, turn the clipper on to help work the oil in.