Hand Tools Used to Accurately Measure Machined Parts
Calipers and micrometers are very commonly seen in use by precision machined component manufacturers. Although a hand tool, these devices provide machinists with valuable measurements during the manufacturing process. Modern hand tools such as calipers and micrometers have come from a long history of use and now are at an even higher level of quality than ever before. Going back millennia, the first calipers were thought to be used by the Greeks and then the Romans. Made from wood, measurements were taken for various purposes. Between the 16th and 19th centuries, there was a significant leap in the Calipers technology by use of the Vernier Scale. This concept was developed by Portuguese mathematician Pedro Nunes in 1542, but it was the French mathematician Pierre Vernier who is credited with refining it in the 17th century. The vernier scale allowed for highly accurate readings on calipers, significantly improving their precision. Modern calipers are attributed to Joseph R. Brown who in 1851 is credited with creating the first commercially viable modern calipers. This design made calipers more affordable and accessible to a wider range of machinists and craftspeople. The modern digitized versions used for precision machined parts allow electronic calipers to display readings on a screen, eliminating the need to interpret vernier scales and offering even greater ease of use. The history of micrometers has its origin associated with astronomy. William Gascoigne, an English astronomer, in the 1600s. He invented the micrometric screw, an essential element for precise measurement. This screw was initially used in telescopes to measure the angular distances between stars. Around 1775, James Watt, the famous inventor of the steam engine, is documented to have used a tool with a micrometer screw for end measurements. In 1848, Frenchman Jean Laurent Palmer created the first documented handheld micrometer with a screw mechanism. This design, often called the “Palmer system,” paved the way for the modern micrometer. Around 1867, the American company Brown & Sharpe, inspired by Palmer’s design, began mass-producing micrometers with the 20th century seeing further refinements to the micrometer design, with improvements in materials and manufacturing techniques. Additionally, specialized micrometers were developed for various measurement needs, such as sheet metal micrometers and internal micrometers. With developments in these tools machining parts manufacturers continue to use calipers and micrometers for their precise measurements. It allows machinists to qualify their work and proceed with the knowledge the precision manufactured components will be done to high quality standards. Here are some examples of the measurements calipers and micrometers provide in the production of precision machined parts and applications:
Caliper Measurements and Accuracy:
- Types of Calipers: There are two main types of calipers with varying accuracy levels:
- Vernier Calipers: These offer a good balance between affordability and precision. They typically have an accuracy of 0.1mm (0.004 inches) using the vernier scale.
- Digital Calipers: These offer the highest readability and ease of use, with an accuracy ranging from 0.01mm (0.0004 inches) to 0.001mm (0.00004 inches) for high-precision models.
- Measurement Range: The measurement range of calipers varies depending on the model. Typical ranges are:
- Vernier Calipers: 100mm (4 inches) to 300mm (12 inches)
- Digital Calipers: Like vernier calipers, with some extending up to 600mm (24 inches).
- Caliper Applications: Machining and metal working, construction, science and education, jewelry making and automotive repair.
Micrometer Measurements and Accuracy:
- Micrometer Range: Micrometers typically have a smaller measurement range compared to calipers, focusing on high precision for small dimensions. Common ranges are:
- Outside Micrometers (OD Micrometers): 0-25mm (1 inch) up to 0-300mm (12 inches)
- Inside Micrometers (ID Micrometers): For measuring internal diameters, these typically range from 25-50mm (1-2 inches) up to 100-200mm (4-8 inches)
- Micrometer Accuracy: Micrometers are known for their exceptional precision:
- Standard Micrometers: These typically offer an accuracy of 1µm (0.00004 inches).
- High-Precision Micrometers: For even greater accuracy, some models boast an impressive 0.1µm (0.00001 inches).
- Micrometer Applications: Precision machining, tool and die making, metrology, medical device manufacturing, electronics manufacturing.
For precision machined components manufacturers, it is important to have calipers and micrometers calibrated and serviced routinely. They provide accurate measurements that advancing technologies require. Machinists must be aware of the use and best practices of the tools. For example, calipers are great but for measuring smaller parts, a micrometer may be a better fit. Environmental conditions can affect the accuracy of a caliper while micrometers are more sensitive to damage and need additional care in handling than calipers to maintain the level of accuracy they provide. You will see both hand tools in use by machined components manufacturers since they complement each other and are part of the manufacturing process, providing the essential and needed precision parts and components to countless industries.