Precautions for using calipers

Calipers have many advantages such as multiple measurement modes, easy operation, durability, strong versatility, and low cost, making them the most common measuring tool in the toolbox. However, there are still many precautions to be taken when using calipers correctly. Let's start with the error factors that affect the measurement results.

When using a caliper for measurement, there are various factors that can cause errors, such as parallax, errors caused by structural non-compliance with the Abbe principle, thermal expansion effects caused by temperature differences between the caliper and the workpiece, and so on.

In addition, due to the lack of a constant pressure device on the caliper, it is difficult to grasp the appropriate and uniform force during measurement, which is also another factor that causes errors.

The structure of the caliper does not comply with the Abbe principle

The reading and measuring axes of a caliper do not comply with the Abbe principle due to different axes. Therefore, when using a caliper, there is a risk of increasing measurement error by measuring the root or tip of the measuring claw. When measuring, it is necessary to pay attention to the workpiece being measured being as close to the ruler body as possible (reading axis).

When checking whether the cursor tick marks align with the major tick marks, look directly at the cursor tick marks. There is a step height difference between the scale surface of the vernier and the main ruler, which can easily cause reading errors. As shown in the following figure, if you observe the cursor scale line from an oblique direction, it will generate the following Δ The error indicated by X. In order to avoid the influence of this factor, the JIS specification specifies that the step height (H) should not exceed 0.3mm.

bend

If the surface guiding the sliding of the vernier scale is bent, it will cause an error as shown in the following figure. This error can be expressed using the same calculation formula as the error that does not comply with the Abbe principle.

Example: Assuming that the deformation caused by the bending of the guiding ruler surface is 0.01mm/50mm, and the tip of the outer diameter measuring claw is 40mm, calculate:

F=40mm × 0.01 ÷ 50=0.008m

The body of the caliper is generally made of stainless steel, which has the same thermal expansion coefficient (10.2 ± 1) as iron based metals × 10-6/K, when measuring, it is necessary to consider the influence of the material of the tested object, room temperature, and workpiece temperature on the measurement.

The caliper measuring claws are very sharp, so the instrument must be operated carefully to avoid personal injury.

Avoid damaging the scale of the digital caliper, and do not engrave identification numbers or leave other information with an electric pen.

Avoid colliding with hard objects or falling on stools or floors to damage the caliper.

Before using a caliper, use a soft dry cloth to wipe off dust and dirt on the sliding and measuring surfaces.

Clamp a clean piece of paper between the outer claws and slowly pull it out. Before using the caliper, close the measuring claw and ensure that the vernier scale (or display) is reset to zero. When using a digital caliper, please reset (reset button) after replacing the battery.

After using the caliper, thoroughly wipe off the water and oil. Then, gently apply rust preventive oil and let it dry before storing.

Waterproof calipers, in order to prevent rusting after use, also need to wipe off the moisture from the calipers.

Avoid direct sunlight, high temperatures, low temperatures, and storage in high humidity environments.

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

During storage, do not completely close the outer measuring claws of the caliper.

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In July 2019, Minghui Company signed contracts with Korean clients for J58A-4000T and J58A-630T

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Qingdao Minghui Metal Forming Machinery Co.,Ltd specializes in the production of J58A series electric CNC Screw press and FP/MP series hot die forging presses. The company has a strong technical force. Since its inception, the company has been adhering to the business philosophy of "responsibility, integrity and pragmatism", and has been forging ahead in business activities.

Qingdao Minghui Metal Forming Machinery Co.,Ltd

Address: Taiwan Industrial Park, Jiaozhou City, Qingdao, Shandong
E-mail: sales@qdmhjx.com

Contacts: Mr Wang
Phone: +86 18663977787

Fax: 86-0532-83281398

Address: Taiwan Industrial Park, Jiaozhou City, Qingdao, Shandong
E-mail: sales@qdmhjx.com

Contacts: Mr Wang
Phone: +86 18663977787

Fax: 86-0532-83281398