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Schmidt Hammer Calibration and Maintenance: Expert Tips and Tricks
March 14,2023

There are many types of rebound hammers. This issue mainly introduces the basic requirements of medium-sized rebound hammers for testing the compressive strength of ordinary concrete.schmidt rebound hammer.webp

Skills requirement:

1. Schmidt rebound hammer can be digital or mechanical.

2. The rebound hammer should have a product qualification certificate and a measurement verification certificate, and the name, model, manufacturer’s name (or trademark), and factory number should be marked on the obvious position of the rebound hammer.

3. Other  requirements:

1) When hitting horizontally, the nominal energy of the hammer should be 2.207J at the moment when the hammer is unhooked;

2) At the moment when the bouncing hammer collides with the bouncing rod, the bouncing spring should be in a free state, and the take-off point of the bouncing hammer should be at "0" on the scale indicated by the pointer;

3) On a steel anvil with a Rockwell hardness HRC of 60±2, the rate setting of the rebound hammer should be 80±2;

4) The digital rebound hammer should be equipped with a pointer direct reading display system. The difference between the rebound value displayed by the digital display and the direct reading value of the pointer should not exceed 1.

4. The ambient temperature when the hammer is used should be (-4~40) ℃.

Verification of rebound instrument:

1. The verification cycle of the rebound hammer is half a year. When the rebound hammer has one of the following conditions, it should be verified by the legal metrological verification institution:

1) Before the new hammer is used;

2) Exceeded the valid period of verification;

3) The difference between the rebound value displayed by the digital rebound meter and the pointer direct reading value is greater than 1;

4) After maintenance, the rate-setting value on the steel anvil is unqualified;

5) Suffer severe impact or other damage.

2. The calibration test of the rebound hammer should meet the following requirements:

1) The calibration test should be carried out at room temperature (5-35) °C;

2) The surface of the steel anvil should be dry and clean, and it should be firmly placed on a rigid object;

3) The rebound value should be the average value of the stable rebound results of three consecutive downward bounces;

4) The calibration test should be carried out in four directions, and before each direction is ejected, the ejection rod should be rotated 90 degrees, and the rebound value in each direction should be 80±2.

3. The steel anvil used in the calibration test of the rebound hammer should be sent to the authorized metrological verification institution for verification or calibration every 2 years.


1. When the hammer has one of the following conditions, it should be maintained:

1) Hammer rebounds more than 2000 times;

2) The rate-setting value on the steel anvil is unqualified;

3) There is doubt about the detection value.

2. The maintenance of the rebound hammer should be carried out according to the following steps:

1) Unhook the spring hammer first, take out the movement, then remove the spring hammer, take out the buffer compression spring inside, and take out the spring hammer, spring, and spring seat.

2) Clean all parts of the movement, and focus on cleaning the inner holes and impact surfaces of the center guide rod, ejection hammer, and ejection rod. After cleaning, a thin layer of watch oil should be applied to the center guide rod, and oil should not be applied to other parts.

3) Clean the inner wall of the casing, remove the scale, and check the pointer. The friction force should be (0.5-0.8) N.

4) Calibrate according to the provisions of this regulation.

5) During maintenance, do not rotate the fixed and fastened zero adjustment screw on the tail cap, and do not make your own or replace parts.

6) For the digital hammer, should also be maintained according to the maintenance procedures required by the product.

3. After the hammer is used, the bullet rod should be extended out of the casing, and the dirt and dust on the bullet rod, the spherical surface of the front end of the rod, the surface of the scale, and the shell should be removed. When the rebound instrument is not in use, the bullet rod should be pressed into the casing, and the button should be pressed after the bullet is fired to lock the movement, and then put into the instrument case. The instrument box should be placed flat in a dry and cool place. When the digital rebound hammer is not used for a long time, the battery should be taken out.



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