Precautions for the Use of Calliper

Precautions for the use of Calliper

Contents

Calliper has a variety of measuring modes, easy to operate, durable, versatile, and low cost, and can be said to be the most common measuring tool in the toolbox.

However, there are a lot of matters needing attention to the correct use of calipers. Let’s start with the error factors that affect the measurement results.

1. Error Component

When measuring with calipers, many factors cause errors, such as parallax, errors caused by structure, not by the Abbe principle, thermal expansion caused by the temperature difference between calipers and workpieces, and so on.

In addition, because the caliper has no constant pressure device, it is difficult to grasp the appropriate and uniform force measurement when measuring, which is another factor causing errors.

Precautions for the use of Calliper

2. The Structure of Calipers Does Not Conform to Abbe’s Principle

The reading number axis and measuring axis of calipers do not conform to the Abbe principle because of different axes.

So when using calipers, the root or tip of the claw is used to measure, and there will be a risk of increasing the measurement error.

When measuring, it should be noted that the measured workpiece should be as close to the ruler body as possible (reading number axis).

Precautions for the use of Calliper

3. Read the Parallax of the Scale

Look directly at the cursor scale when checking that it is aligned with the main scale divider.

The difference in height between the vernier caliper and the main ruler scale surface is easy to cause a reading error.

As shown in the figure below, if the cursor scale is viewed from an oblique direction, the error shown in Figure ΔX will result.

To avoid this effect, the JIS specification states that the step height (H) should not be greater than 0.3mm.

4. Bending of Datum End Face

The bending of the ruler that guides the ruler to slide will result in an error as shown in the figure below, which can be expressed by the same calculation formula as the error that does not conform to Abbe’s principle.

Assume that the deformation caused by the bending of the guide ruler is 0.01mm/50mm, and the tip of the outside diameter is 40mm to calculate: f=40mm×0.01÷50=0.008mm

5. The Relationship Between Measurement and Temperature

The body of the caliper is generally made of stainless steel, which has the same thermal expansion coefficient (10.2±1)×10-6/K as iron metal.

The influence of the material of the measured object, room temperature, and the temperature of the workpiece on the measurement should be considered when measuring.

Precautions for the use of Calliper

vernier caliper

6. Precautions in Operation

The calipers are very sharp, so the instrument must be handled with care to avoid personal injury.

Avoid damaging the scale of the digital caliper. Do not encode the identification number or leave other information with the electric pen.

Precautions for the use of Calliper

7. Maintenance of Sliding Surfaces and Measuring Surfaces

Before using calipers, wipe away dust and dirt on sliding and measuring surfaces with a soft, dry cloth.

8. Check and Calibrate the Origin Before Use

Clip a clean piece of paper between your outer PAWS and slowly pull it out.

Close the caliper and make sure the vernier scale (or display) is set to zero before using the caliper.

When using digital calipers, reset the battery after replacing it (zero buttons).

Precautions for the use of Calliper

9. Operation After Use

After using the caliper, wipe off the water and oil thoroughly. Then, lightly smear with anti-rust oil and let dry before storing.

Waterproof calipers, to prevent the occurrence of rust after use, also need to wipe the water calipers.

10. Storage Precautions

Avoid direct sunlight, high temperature, and low temperature, and store in high humidity.

If digital calipers are not used for more than three months, remove the battery before storage.

Do not allow the outside measuring claw of the caliper to be completely closed during storage.

gavin yi
CEO & Project Manager
Shenzhen Yijin Hardware Co., Ltd.

Gavin Yi

Gavin Yi is a distinguished leader in precision manufacturing and CNC technology. As a regular contributor to Modern Machine Shop and American Machinist magazines, he shares expertise on advanced machining processes and Industry 4.0 integration. His research on process optimization has been published in the Journal of Manufacturing Science and Engineering and International Journal of Machine Tools and Manufacture.

Gavin serves on the National Tooling & Machining Association (NTMA) board and frequently presents at the International Manufacturing Technology Show (IMTS). He holds certifications from leading CNC training institutions including Goodwin University’s Advanced Manufacturing program. Under his leadership, Shenzhen Yijin Hardware collaborates with DMG Mori and Haas Automation to drive innovation in precision manufacturing.

gavin yi

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