As a classic weighing device, the core structure of the mechanical scale consists of four parts: the load-bearing device, the lever system, the reading device and the scale body, which shows the perfect combination of precision engineering design and mechanical principles. The load-bearing device is a key component that is in direct contact with the object to be measured. It is usually made of high-strength metal plates and is precisely processed to ensure uniform distribution of force, thereby improving the accuracy and stability of weighing.

The lever system is the core of the mechanical scale and is designed using the principle of unequal arm levers. Its structure is composed of a long lever and a short lever connected in parallel to form a composite lever system. This design enables small mass changes to be converted into significant displacement changes through the amplification effect of the lever, thereby significantly improving the sensitivity and accuracy of the measurement.

The reading device is a key link for the mechanical scale to display the value. As a typical reading structure, the fulcrum knife and the load-bearing knife embedded on the beam of the scale head constitute a precise torque balance system. The main scale is engraved with a 5,000 kg scale, while the sub-scale provides a 200 kg subdivision scale. The combination of the two achieves complete range coverage. As a displacement indicating element, the surface of the free weight is treated with nickel plating, chrome plating and other anti-corrosion treatments to ensure the accuracy and stability in long-term use. When the object to be measured is placed on the load-bearing device, the lever system transfers the gravity to the metering lever, and the system is balanced by manually increasing or decreasing the weight or moving the free weight. At this time, the position of the free weight on the scale corresponds to the mass value of the object to be measured.

During the measurement process, the mechanical scale follows the strict principle of mechanical balance. When the object to be measured applies gravity, the force point knife of the long lever transfers the force to the metering lever to form an initial torque. By adjusting the number or position of the weight, the length of the force arm or the magnitude of the force value is changed, so that the metering lever reaches a new equilibrium state. In this equilibrium state, the displacement of the free weight on the scale and the mass to be measured show a linear relationship, and its mathematical model can be expressed as: mass to be measured = free weight indication × scale division value. The design of the secondary scale further improves the measurement accuracy. Its 200 kg subdivision scale is effectively supplemented by the minimum division of the main scale through the cooperation of the weight and the scale.

In terms of accuracy assurance, the mechanical scale adopts multiple design strategies to ensure its long-term stability and reliability. The hardness matching of the knife and the knife bearing is strictly calculated. Usually, the hardness of the knife bearing is 3-5RC higher than that of the knife to ensure wear resistance in long-term use. As key force transmission components, the material selection and heat treatment process of the lifting lug and the lifting ring directly affect the overall stability of the system. For scales below 3 tons, ordinary carbon steel is used for carburizing, while scales above 3 tons are upgraded to alloy tool steel, and the stress calculation is multiplied by the surplus coefficient of 1.3-1.4 to ensure the strength and stability of the structure. The adjustment mechanism of the balance weight is realized by a screw rod and a double nut structure, and its adjustment range covers the entire scale range to ensure the initial balance in the empty scale state.