Appendix
Do not measure test pieces that exceed the maximum hardness limits
of your impact device:
Impact device type
Maximum hardness
D – DC – DL – E
890 HL (68 HRC)
C
960 HL (70 HRC)
G
750 HL (645 HB)
To obtain precise measurements the following minimum mass and
thickness requirements must be met:
Impact device type
D/DC
D+15
DL
C
G
E
Minimum test piece weight ( kg / pounds )
Stand alone
5/11
5/11
5/11
1.5/4.
9
15/
33
5/11
With support
2/4.4
2/4.4
2/
4.4
0.5/1.
1
5/11
2/
4.4
Coupled
0.1/
0.22
0.1/
0.22
0.1/
0.22
0.02/
0.04
0.5/1.
1
0.1/0.
22
Minimum test piece thickness ( mm / inch )
Coupled
3/6.6
3/6.6
3/
6.6
1/ 2.2
10/
22
3/
6.6
Superficial
0.8/
1.76
0.8/
1.76
0.8/
1.76
0.2/0.
44
—
0.8/
1.76
When working with a portable hardness tester you should always
average at least 3 measurements (the QH5 does real time statistics) and
the measurements must be made at no more than 4mm from one
another. The results of these measurements should do not differ in
more than ±6 HLD units. If a difference of ±6 HLD units is obtained
check test conditions and measure again.
