Blade length
The length of the cutting part of the scissors; in manual and similar models (see "Type") the cutting part is called sponges, in lever and guillotine models — blades.
When working on sheet metal, the long blades/jaws allow you to make a long cut in one bite, but impair the manoeuvrability of the scissors. Therefore, models with relatively long jaws (from 50 mm) are mainly used for straight cuts, and short scissors are more convenient for curly lines. Also note that in bolt cutters and other tools designed for large thick parts, the jaws are also made short — this design is optimal for working at high forces.
Steel hardness (HRC)
The hardness of the steel from which the scissors are made — or at least the cutting part of the scissors (handles and other elements can be made of other types of metal, softer). Indicated on the Rockwell scale in points; the higher the score, the harder the steel.
The general rule is that the hardness of the cutting edges should not be lower than the hardness of the material being cut — otherwise the quality of the work will noticeably deteriorate, up to the complete impossibility of making a cut. The minimum hardness found among metal shears is 40 HRC, and the highest is about 65 HRC. Most often, this is quite enough: most of the metals that you have to work with with scissors, without special hardening, have a hardness of up to 25 – 30 HRC. But if the tool is planned to be used for high-strength alloys, it is worth clarifying whether its hardness will be enough for this.
Also note that higher hardness increases the overall efficiency of the tool and allows it to retain sharpness for a long time; on the other hand, as hardness increases, the metal becomes more brittle and harder to sharpen. Conversely, softer steel is relatively quickly wrinkled and blunted, but it is also restored without much difficulty.
Length
The total length of the tool.
This parameter is specified for manual sheet metal shears (see "Type") and tools of a similar design. In addition to dimensions, it determines another important point — the working force. The greater the length of the scissors, other things being equal, the greater the length of the lever that the user acts on, and the greater the force transmitted to the jaws with the same pressing force. Accordingly, tools for working with thick and hard materials inevitably turn out to be long (for example, the length of a bolt cutter can exceed 1 m). And short handles make the scissors easy to store and transport, but require more effort when working.
