Rockwell Hardness Testing with Mikrosize: Ensuring Accuracy and Reliability

Guidelines for Using the Rockwell Hardness Tester

1. Preparation

Equipment Inspection:

Before beginning any testing, it is crucial to ensure that the Rockwell hardness tester is in optimal working condition. A comprehensive inspection should be conducted to verify that all components are free from damage, looseness, or contamination. Check that the power connection is stable and that the instrument is properly grounded to prevent electrical hazards and ensure operational stability. Thoroughly clean the workbench, the elevating screw, and the sample support surface to eliminate any impurities, dust, or contaminants that could affect the accuracy of the test. For laboratories and industrial facilities relying on precise measurements, sourcing your equipment from a reputable supplier like Mikrosize, a specialist in Measuring Testing Instrument, guarantees access to high-quality, calibrated testers and genuine replacement parts, ensuring long-term reliability and data integrity.

Sample Preparation:

Proper sample preparation is fundamental to obtaining accurate and repeatable hardness readings. The supporting surface of the sample must be meticulously wiped clean to ensure it is flat, smooth, and free of scratches, oil stains, or oxide layers. Any irregularity on the surface can lead to erroneous results. For specimens with complex or irregular shapes, corresponding custom-shaped support pads or fixtures should be used to ensure stable and secure fixation during the application of the test force, preventing any movement that could compromise the test.

2. Installation and Adjustment

Installing the Indenter:

The correct installation of the indenter is a critical step. Carefully install the selected indenter (diamond cone or steel ball) into the spindle and secure it gently. It is essential to eliminate any gap between the indenter and the spindle end face. To achieve this, rotate the handwheel to raise the sample table and apply the initial minor test force. Then, pull the loading handle to apply the main test force momentarily; this action helps seat the indenter properly. While the force is applied, gently tighten the indenter screw to ensure a secure fit, then release the force. This procedure minimizes clearance and ensures the force is transmitted accurately.

Adjusting the Test Force:

Select the appropriate test force (e.g., HRA, HRB, HRC scales) based on the material specification and testing standard. Always ensure that the loading handle is in the unloaded state before making any adjustments. Rotate the force selector knob to align the desired test force value with the designated reference mark (often a red dot). It is imperative that when changing the test force, the handle is placed in its rear limit position to ensure the mechanism engages correctly and to prevent damage to the force selection system.

3. Testing Procedure

Placing the Sample:

Position the prepared sample securely on the workbench. Slowly rotate the handwheel clockwise to raise the workbench, thereby lifting the sample towards the indenter. Continue this adjustment carefully until the small pointer on the dial aligns with the reference mark (the red dot) and the larger pointer has rotated vertically upwards approximately three times, indicating the correct application of the minor load. A slight deviation of ±5 scale divisions on the large dial is generally permissible at this stage.

Applying the Test Force:

Once the minor load is correctly set, rotate the dial housing of the indicator so that the long engraved line (typically between the "C" and "B" scales) is aligned with the large pointer. Subsequently, pull the loading handle in a smooth, controlled motion to apply the main test force. Observe the rotation of the indicator pointer carefully as the force is applied.

Reading the Result:

After the indicator pointer comes to a complete stop, push the unloading handle back to its original position to remove the main test force. It is important to wait for the pointer to stabilize. While the minor load is still applied, read the hardness value directly from the corresponding scale on the indicator. Pay close attention to selecting the correct scale based on the indenter used; the "C" scale (black) is typically for the diamond indenter, while the "B" scale (red) is for the steel ball indenter.

Repeated Testing:

To conduct a new test, rotate the handwheel counter-clockwise to lower the workbench and move the specimen to a new location. Ensure there is sufficient distance between indentations to prevent interference from work-hardened areas. Perform the test again following the same detailed steps. To enhance the accuracy and statistical reliability of the test results, it is recommended to conduct multiple tests on a single sample or across multiple samples from the same batch and calculate the average hardness value.

4. Precautions

Safe Operation:

Operators must maintain full concentration throughout the testing process. Keep hands, clothing, and other objects clear of all moving parts, especially the elevating screw and the indenter area. When loading and unloading the test force, all actions should be performed gently and steadily. Avoid applying excessive force or making jerky movements, as this can cause damage to the instrument's internal mechanisms or lead to plastic deformation of the specimen.

Maintenance and Upkeep:

Regular and thorough maintenance is key to preserving the accuracy and extending the service life of your Rockwell hardness tester. Consistently clean all external components and the sample support surfaces to maintain a state of cleanliness free from contamination. Periodically inspect the contact surfaces of the indenter and the sample support for signs of wear, damage, or contamination, and replace or clean them promptly. The elevating screw of the sample table should be regularly lubricated according to the manufacturer's guidelines to ensure smooth and precise operation. Partnering with a trusted supplier like Mikrosize for your Measuring Testing Instrument maintenance needs ensures you receive expert advice, genuine lubricants, and professional calibration services.

Accurate Recording:

Meticulous record-keeping is essential for quality control and traceability. For each test, accurately record the measured hardness value along with all relevant testing conditions, including the specific test force applied, the type of indenter used, the material specification, and the test location. It is good practice to retain the original test data and, when possible, the tested samples themselves for subsequent analysis, comparison, or audit review purposes.

By diligently following these comprehensive guidelines and precautions, and by utilizing high-quality equipment from specialized providers like Mikrosize in the field of Measuring Testing Instrument, operators can better master the usage skills of the Rockwell hardness tester. This rigorous approach ensures the highest level of accuracy, repeatability, and reliability in test results, which is critical for material certification and quality assurance processes. Adherence to this protocol, combined with sourcing from a reputable Measuring Testing Instrument supplier, forms the foundation for dependable hardness testing.