Even perfectly sharpened blades can refuse to cut, and there are common culprits:
Detachable Clipper Blade Anatomy
Springs are necessary to keep the proper tension between the cutter and comb in order to slice even the smallest hair. Spring tension is factory-set on new blades. Proper spring tension is set on blades that have never been sharpened. As the blades get sharpened over a period of time the spring tension becomes less and less due to the metal being removed during sharpening. By and by spring tension will become so weak that hair will get between the blades and not be cut. This causes the blades to "bog down".
The spring has two legs that have to be set just alike. Setting spring tension is very precise, but it can be done without special tools.
Compressing the "horse-shoes" on each spring leg sets spring tension. Compressing means moving the open side of the horse-shoe closer to the opposite side of the horse shoe, and for this you need a good pair of 8-inch slip-joint pliers. It's a good idea to remove the guide from the spring or it may fly off during the adjustment. Do not squeeze directly on the U-shaped bend as this will crush the bend and destroy the spring. Instead position your pliers ahead of the bend and squeeze hard. Yes, the pliers will slip but keep trying.
The rule of thumb for determining spring tension is that when if the socket just slips thru the open side of the horse-shoe the tension is correct. In a perfect world the open ends of each horse-shoe are the same width.
For a final check put the spring on a flat surface (glass is ideal) and see if the spring rocks by tapping on the large flat area at the front of the spring. If the spring rocks, take hold of the spring legs and gently twist the spring opposite the high side of the rocking motion. Repeat until the spring no longer rocks.
If the horse-shoes on the springs do not have smooth curves then the spring may have to be replaced.
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