How does the hardness of the steel affect the performance of haircutting shears?
Many manufactures of scissors will advertise that their scissors are very hard, and therefore are of the best quality. Usually they will state the Rockwell Scale measured hardness of their steel or they may refer to the inclusion of a hardening element in their steel such as Cobalt or Tungsten. The hardest steel may not, however, make the best shear for your personal requirements.
Typical stainless steels used in scissors range from about (Rockwell Measurement Scale) Rc 48 to Rc 62. High quality precision shears generally range from Rc 54 to Rc 62 (shears softer the Rc 53 tend to be lower quality economy scissors). Generally the harder steels are more resistant to wear and therefore will hold their edge longer. However the harder steels are often more brittle and will tend to chip and nick along the edge more easily when dropped or roughly handled.
The slightly softer steels are more flexible giving the blades a toughness that resists chipping and nicking. The softer steels also have the potential to be sharpened to a sharper edge (good for slide cutting) even though that sharper edge may not last as long as the less keen edge on a very hard blade. The less keen but more durable edge on a very hard steel blade will tend to give a more “crisp” feeling to the cut and will usually cut with more noise than the very quiet and smooth cutting typical of a good edge on a slightly softer high quality steel scissors.
So far there is no one steel that gives both the ultimate smooth quiet cut and the longest lasting edge together in the same scissors. There is a balance that you must choose for yourself to suit your own style.