The metal caliper, as a fundamental measuring tool in the machinery manufacturing industry, the advantages of modern
metal calipers mainly lie in high precision, strong durability, and the absence of power requirements. According to data
from the International Organization for Standardization, the measurement accuracy of high-quality metal calipers can
reach ±0.02mm, and their service life is typically over 20 years. The hardness of steel calipers reaches HRC58-62,
and after chrome plating treatment, their corrosion resistance increases by more than 85%. However, the disadvantages
of metal calipers are also quite obvious, including large reading errors, low operational efficiency, and strong temperature
sensitivity. Market research shows that the human reading error of traditional metal calipers is ±0.05-0.1mm, which is
5-10 times higher than that of digital calipers.
I. Structural Advantages and Precision Characteristics of Metal Calipers
1. The structural advantages of metal calipers stem from their all-steel integrated design. The main scale and the
vernier scale are forged from high-quality tool steel and undergo heat treatment, resulting in a hardness of HRC 58-62,
which ensures good rigidity and stability. The thickness of the scale body is typically 6-10mm, the width is 15-25mm,
and the weight distribution is uniform, providing a stable operation feel. The inner and outer measuring jaws are
precisely ground, with a flatness control of 0.002mm and a verticality deviation of less than 0.01mm. The depth
measuring rod has a diameter of 4-6mm, with a hard chrome coating on the surface, achieving a hardness of HRC
65 or above, and has excellent wear resistance. The scale lines are laser engraved or chemically etched, with a line
width of 0.05-0.08mm and a depth of 0.01-0.02mm, ensuring clarity and durability.
2. The classification system for accuracy levels is well-established. The international standard divides the accuracy levels
into three grades: 0, 1, and 2. Grade 0 precision calipers have a measurement error within ±0.02mm, and are mainly
used for precise measurement and standard transmission. Grade 1 calipers have a measurement error of ±0.03mm,
suitable for general precision processing. Grade 2 calipers have a measurement error of ±0.05mm, meeting the
requirements of ordinary mechanical processing. The measurement range covers various specifications such as
0-150mm, 0-200mm, and 0-300mm, and large calipers can reach 0-1000mm. The stability of accuracy is the core
advantage of metal calipers. Under normal usage conditions, the annual accuracy variation rate is less than 0.005mm,
which is much lower than that of electronic measuring tools.
3. The material properties determine the reliability of the metal calipers. High-quality calipers are made of chromium
-molybdenum steel or stainless steel, with tensile strength ranging from 800 to 1200 MPa and yield strength ranging
from 600 to 900 MPa. Surface treatment processes include chrome plating, nitriding, and DLC coating, which enhance
corrosion resistance and wear resistance. The chrome layer thickness is 5-15 μm, with a hardness of HV800-1000,
capable of resisting general acid and alkali corrosion. The material stability ensures the measurement accuracy
of the calipers under different environmental conditions. The linear expansion coefficient is controlled within
11×10⁻⁶/℃, and the temperature compensation characteristics are good.
II. Convenience of Use Advantage
1. The power-free design is one of the significant advantages of the metal caliper. It does not require battery power,
avoiding issues such as insufficient battery life and circuit failures, and is particularly suitable for harsh
environments and long-term storage use.
2. Excellent waterproof and dustproof performance, with a protection level of up to IP54-IP65, enabling normal operation
in humid and dusty environments. It has strong shock resistance, capable of withstanding a drop from a height of 3-5
meters without affecting accuracy.
3. Strong immunity to magnetic field interference, and measurement data will not be affected in a strong electromagnetic
environment. The storage temperature range is -40°C to +80°C, and the working temperature range is -10°C to
+50°C, offering wide adaptability.
III. Analysis of operational efficiency
1. The simplicity of operation is reflected in the intuitive reading method. The principle of the cursor reading is
straightforward and simple, requiring no complex operation procedures. The training time for beginners usually only takes
1-2 hours. The scale is clear, and the reading accuracy is high under good lighting conditions. The design of the fastening
screws is reasonable, which can effectively fix the measurement position and avoid errors during the reading process.
The operation reliability is high, and the mechanical structure will not have software failures or data loss problems.
Maintenance is simple, only requiring regular cleaning and rust prevention treatment. The cost of use is low.
2. The multi-functional measurement capabilities meet various requirements. The inner diameter measurement
accuracy is ±0.03mm, suitable for measuring hole diameters and slot widths. The outer diameter measurement accuracy
is ±0.02mm, suitable for measuring shaft diameters and plate thicknesses. The depth measurement accuracy is
±0.05mm, suitable for measuring step heights and blind hole depths. The marking function facilitates marking of
workpieces and processing positioning. The measurement range is wide, and a single caliper can complete various
geometric measurements, reducing the frequency of tool replacement and improving work efficiency. The standardization
level is high, conforming to international standards such as GB/T1214 and ISO13385, and the measurement results have
comparability and traceability.
IV. Efficiency Limitations and Operational Complexity
1. The relatively low measurement efficiency is a significant drawback of metal calipers. The single measurement
process typically takes 15-30 seconds, including steps such as positioning, reading, and recording. Data recording
relies on manual copying, which is prone to errors, with error rates ranging from 2% to 5%. It cannot directly output
digital signals and cannot be integrated with automated systems, limiting its application in modern manufacturing
environments.
2. The operation skills are highly demanding, which hinders their wide application. The correct holding method
and measurement techniques require specialized training, and the training period usually lasts for 1 to 2 weeks.
The skill of reading the numbers is difficult to master, and beginners often make mistakes in reading
decimal places.
3. Limited data processing and analysis capabilities. Unable to achieve real-time data collection and transmission,
which hinders the control of the production process. Statistical process control (SPC) analysis requires additional data
processing work. It is difficult to trace measurement results, lacking timestamps and operator information.
The integration level of informatization is low, failing to meet the requirements of Industry 4.0
and intelligent manufacturing.
