Dial indicators » precise measuring tools for the finest measurements
Many do-it-yourselfers are familiar with how to use a caliper. However, measuring devices such as the micrometer screw (for components) or the dial indicator are less common. The dial gauge is particularly suitable for precisely recording differences in length. But how does a dial gauge work? What special features do digital versions offer compared to analogue versions, and what criteria are important when purchasing?
Our guide provides answers to:
- What characterizes a dial gauge?
- How does a dial gauge work?
- What aspects should be taken into account when purchasing?
The dial gauge: A short explanation
Instruments that precisely determine length deviations have been around since the 19th century. They offer detailed insights into the condition of the surface and possible deformations of components.
Dial indicators are particularly in demand among workshops and dedicated DIY enthusiasts, especially when it comes to quality testing of parts. This can be used, for example, to precisely check the concentricity of rotating machine components such as wheels, rotors, crankshafts or even engines.
To carry out the measurement, the measuring probe of the dial indicator is gently pressed onto the workpiece, which is then rotated. Every longitudinal displacement is recorded by the dial indicator. An analog pointer or a digital display provides information about whether the measured surface is flat.
In order to correctly measure a rotating workpiece, it must be moved, and the dial indicator must be moved synchronously. In most cases this is made possible by a tripod for the dial indicator. This tripod ensures that the measuring device stands firmly and can be optimally positioned thanks to its adjustable joints.
Expert recommendation: pay attention to the reference temperature
Workpieces can expand or shrink as room temperatures fluctuate, which is why a consistent reference temperature is required for precise measurements. During calibration, dial indicators are always adjusted to 20 degrees Celsius.
After the measurement is completed, a spring mechanism automatically returns the pointer to the zero point. This resets the dial gauge to its starting state for the next use.
Although a digital dial indicator essentially works according to the same concept, the digital display offers the user easier readability. Reading errors that could arise from an oblique viewing angle with analogue models are avoided here.
Another feature of digital dial indicators are switching options that can be used, for example, to switch between millimeters and inches. This means that the measurement data can be further processed immediately in the desired unit.
What is important when buying?
Whether you prefer an analogue, digital or microcomputer dial indicator depends on your personal taste. However, there are some criteria you should consider before purchasing.
DIN 878 standard
If you want to achieve precise results with a dial indicator, the DIN 878 standard is an essential purchase criterion. But what exactly does this standard say?
DIN 878 ensures that dial indicators can serve as standardized measuring instruments. The gear ratio between the rack and gear should be in the thousandth of a millimeter range. It is essential that all parts involved are of high quality and the measuring range is precisely defined. The standard defines the minimum requirements: With a partial measuring range of 0.1 millimeters, the deviation may be a maximum of five micrometers, and with a total measuring range of 10 millimeters, a deviation of up to 17 micrometers is permitted. The permitted deviations are therefore very small. The standard also specifies that the measuring force must be between 0.3 and 1.5 Newton.
Calibration
As a rule, dial indicators are already calibrated according to the factory standard when purchased, but without an official certificate. For an additional fee, some manufacturers offer versions certified by recognized laboratories.
Measuring inserts
Measuring probes are often referred to as measuring inserts or measuring bolts. This indicates that they are usually not permanently integrated with the dial indicator, but were designed as a changing accessory.
This allows users to replace the measuring insert as needed to ensure optimal adaptation to the workpiece being measured. The materials for measuring inserts vary and can be made of hard metal, ceramic or plastic.
For easy replacement, the measuring inserts are usually equipped with an M2.5 thread. However, in certain cases an adapter may be required.
Digital dial indicators and the software
When choosing a digital model, many manufacturers often offer the option of passing on measurement results via an interface.
Dial indicators with microcomputer
When choosing the microcomputer solution, users receive a complete package of software suite that makes it possible to use the dial indicators on a Windows PC, smartphone or tablet. In addition to the effect that the dial indicators with microcomputers have a lot of other features.