Humboldt H-2987 Concrete Rebound Hammer - Manual (Page 6)

Maintenance
We recommend that you calibrate your Rebound Hammer regularly using
the Humboldt Calibration Anvil, H-2972, ordered separately. For a Rebound
Hammer, you should start verifying the readings after approximately 2,000
uses (or completed tests). You should also verify the readings if you have
reason to suspect that your Rebound Hammer is giving you false data.
Calibrating your Concrete Rebound Hammer
When tested against the Anvil, the impact energy level of the Rebound Hammer
must be 1.64 foot-pounds or .227 kilograms-meter, and the rebound number
must be a value of 80 ±2. As the Rebound Hammer approaches 2,000 uses, it
may start to read outside of the range of 80 ±2 on the test Anvil. At this point
you should calibrate it.
1. With the piston fully extended, twist the cap on the top of the Rebound
Hammer to open it. Keep your hand positioned on the top of the cap, as you
will feel some slight spring compression pushing against the cap. Set the Re-
bound Hammer aside and examine the cap. The cap has an adjustment screw
and nut, which are used to calibrate the Rebound Hammer.
Figure 5: Rebound Hammer cap
2. Using a 10 mm wrench, loosen the adjustment nut away from the cap. If the
Rebound Hammer is reading low, tighten the adjustment screw (clockwise) into
the cap. If the Rebound Hammer is reading high, loosen the adjustment screw
(counterclockwise) away from the cap. When you are finished, tighten the adjust-
ment nut to lock the screw in this new position.
3. Put the Rebound Hammer back together, and test it on the Anvil again to get
a calibrated reading. If it reads 80 ±2, the Rebound Hammer is calibrated. If the
readings fall outside of this range, take the Rebound Hammer apart and try to
adjust it again. Keep adjusting and testing the Rebound Hammer until it reads
80 ±2.
Clean the Rebound Hammer with a dry, clean cloth. Do not use solvents, abra-
sives, or water for cleaning. The springs in the Rebound Hammer may become
Note that some countries have set their own national standards for calculating
test results. Therefore, follow the standards of the country where you are using
your Rebound Hammer.