According to Andis USA, Matthew Andis, Sr., designed and built his electric clippers in 1921, and since 1922, Andis has manufactured clippers and blades for both the professional hairstylist and the home user. Andis also manufactures clippers for both large and small animals. When changing the blades on your Andis clippers, verify you have purchased blades designed to fit your clipper model. Andis clipper blades are not interchangeable from model to model.
Unplug your Andis clippers from the wall outlet and lay them on a flat surface with the blades facing up.
Remove the two screws holding the blades to the clippers with a Phillips screwdriver, turning the screws counterclockwise.
Take the old blades from the Andis clippers and install the replacement blades onto the clippers. Line up the screw holes on the blades with the screw hole openings on the clippers. If your clippers are equipped with an armature pin that is raised on the body of the clipper, make sure the yoke on the back of the replacement blades lines up with the armature pin.
Replace the two screws into the replacement blades and clippers. Tighten the screws on the clippers and blades, turning them clockwise.