Common Faults and Repairs of Hardness Testers

The most commonly used hardness testers in industrial and mining enterprises and scientific research units are mainly metal Rockwell, Brinell and Vickers hardness testers. Among them, the metal Rockwell and metal Brinell hardness testers are simpler in structure than the metal Vickers hardness tester. The adjustment and repair of common faults are not very difficult. The following is an introduction to the common fault adjustment and repair of metal Vickers hardness testers.

Before the calibration and repair work begins, you should start with adjusting the level of the workbench, based on years of work practice. Then observe whether the spindle, lever, lifting screw, buffer mechanism and measuring device are normal and flexible. Ensure that you have a basic understanding of the performance of the equipment. Then solve the problems one by one.

1. The loading indicator light and the measuring microscope light are not on

, then check the switch, bulb, etc. If it is still not on after eliminating these factors, first check whether the hardness tester power supply is connected properly. It is necessary to see whether the load is fully added or whether the reed switch is normal. If it is still abnormal after elimination, it is necessary to start with the line (circuit) and gradually check.

2. The indentation cannot be seen or is not clear, and the turbidity in the measuring microscope

is still not clear after adjustment. This should start with adjusting the microscope focus and lighting. Then you should turn the objective lens and eyepiece separately, and move the three flat mirrors with dotted lines, solid lines, and engraved lines in the mirror separately, carefully observe which mirror surface the problem is on, then remove it, wipe it clean with long-fiber absorbent cotton and anhydrous alcohol, install it in the reverse order and observe, if the problem is still not solved, send it for repair or replace the micrometer microscope.

3. The indentation position changes greatly, the indentation is not in the field of view or the workbench is slightly turned,

so adjust them in the following order. ① Adjust the active clearance at the lower end of the spindle. The reason for this situation is that the axes of the indenter, measuring microscope, and workbench are different because the indenter is fixed at the bottom of the working shaft. The lower end face of the guide seat does not directly contact the spindle cone surface; ② Adjust the side screws of the rotating shaft to make the working axis and the spindle concentric (axis). After adjustment, an indentation is pressed on the test block, observe its position in the microscope, and record it; ③ Gently turn the workbench (to ensure that the test block does not move on the workbench) and find a point on the test block that does not rotate under the microscope. This point is the axis of the workbench; ④ Slightly loosen the screws on the lifting screw pressure plate and the bottom screws, and gently move the entire lifting screw to make the axis of the workbench coincide with the position of the indentation recorded in the measuring microscope, and then tighten the pressure plate screws and adjustment screws to press an indentation for comparison. Repeat the above steps until they are completely coincident.

4. Reasons and solutions for the out-of-tolerance indication during calibration

① The measuring microscope scale is inaccurate. Check with a standard micrometer. If inaccurate, it can be sent for repair or replacement.

② See if it meets the requirements of the diamond indenter calibration regulations. If there is a defect, replace the indenter. The diamond indenter is defective. Observe with an 80x stereo microscope.

③ Check with a small-load third-class standard dynamometer. If the load exceeds the requirement (±1.0%) but the direction is consistent, the negative (load) load exceeds the specification requirements or the load is unstable. In this case, the lever ratio has changed. You can loosen the spindle protection cap, turn the force point contact, adjust the load (lever ratio), and tighten it after adjustment. If the load is unstable, it may be caused by blunt force point blades, wear of fulcrum steel balls, or non-concentricity between the working shaft and the spindle, or greater friction in the working shaft. At this time, check the blades and steel balls. If they are blunt or worn, they should be trimmed or replaced. Check the working shaft and clean it. Be sure to complete the shaft circumference steel balls. See step 3 for coaxial adjustment. (end)