Dial indicator needle in wrong position above the zero point, and the test force exceeds 3000kgf reading line during the test
If the dial indicator needle is above zero in wrong position , and the test force exceeds 3000kgf reading line during the test,usually caused by human knock against the hardness tester or vibration during the transportation of the hardness tester, it is not necessary to calibrate the test force first, but only to calibrate the hardness tester with the test block. If the hardness value is accurate, simply loosen the dial screw anticlockwise, then take the needle out lightly and put it back in the right position and re-tighten the screw clockwise, the calibration steps are as follows:
1. First calibrate the hardness tester with the test block, make the pressure gauge needle reach 3000kgf 3-4 times, then read the Brinell indentation diameter, look up the table to get the Brinell hardness value.
2. After the reset of the needle, use the same test block to calibrate the hardness tester, so that the pressure gauge needle reaches 3000 kgf 3-4 times, and then get the hardness value, compare the hardness value of two times, if the two hardness values are within the index error range, this can prove that there is no problem with the test force and pressure, there is no need to calibrate.