LAAN-A-HN-E002
Material Testing System
No.251
Hardness Test on Propelling Pencil Lead Core by Shimadzu
DUH-W201S Dynamic Ultra Micro Hardness Tester
Propelling (or mechanical) pencil lead cores are made
by mixing black lead with polymer resin. The hardness
symbols HB and B are evaluated by a density
measurement tester according to the density obtained
by drawing on line drawing paper; however, hardness
is not yet scientifically defined.
The following introduces an example of a hardness
test performed on propelling pencil lead cores using
the Shimadzu Dynamic Ultra Micro Hardness Tester.
1. Specimen
1) Specimen name
Propelling pencil lead core
2) Specimen No.
HB
B
2B
No.1
No.2
No.3
3) Specimen size (mm)
φ0.5 × 70
2. Test conditions
1) Testing machine
Shimadzu DUH-W201S
Dynamic Ultra Micro
Hardness Tester (See Fig. 1)
2) Indenter
Triangular pyramid indenter
with tip angle of 115°
(made of diamond)
3) Test type
Load-unload test
4) Test force (mN)
49
5) Loading rate
(mN/sec)
4.413
6) Holding time (sec)
7) Test method
Fig. 1 Overview of DUH-W201S
15
The lead core was inserted
into the propelling pencil and
the tip of the core that was
worn to a flat surface by
drawing a line on paper was
fixed in place by the standard
vise and tested. (See Fig. 2)
Test force
Propelling pencil lead core
Standard vise
Propelling pencil
Fig. 2 Conceptual diagram
No.251
3. Test results
1) Table 1 summarizes the results (mean values) of testing by the test conditions in section 2.
Table 1 Hardness Measurement Results (Mean Values)
Specimen No.
Maximum Force
[mN]
Maximum Depth
[μm]
Dynamic Hardness
[DHT115-1]
HB
No.1
49.32
2.803
24.213
B
No.2
49.28
3.394
16.509
2B
No.3
49.26
3.615
14.543
Specimen Name
Propelling pencil lead core
Remarks) The calculation expression for dynamic indentation hardness is as follows:
DHT115-1 = 3.8584P/h2
where,
DHT115-1: Dynamic hardness of triangular pyramid indenter at load end
P: Maximum Force (mN)
h: Maximum Depth (μm)
2) Fig. 3 shows the force-depth graph after testing.
Force-Depth Graph
50.00
2B
B
Maximum Force (mN)
HB
0.00
0.00
Maximum Depth (μm)
5.00
Fig. 3 Force-Depth Graph
3) The order of specimen hardness in 1) is as follows : HB > B > 2B
This means that HB is about 1.5 times harder than B and B is about 1.1 times harder than 2B.
4) Figs. 4 to 6 show images of the indentation.
Fig. 4 Indentation in HB Core
Fig. 5 Indentation in B Core
Fig. 6 Indentation in 2B Core
4. Summary
The Shimadzu DUH-W Dynamic Ultra Micro Hardness Tester allows the hardness of propelling pencil lead cores to
be evaluated by hardness value and not density.
SHIMADZU CORPORATION. International Marketing Division
3. Kanda-Nishikicho 1-chome, Chiyoda-ku, Tokyo 101-8448, Japan Phone: 81(3)3219-5641 Fax. 81(3)3219-5710
Cable Add.:SHIMADZU TOKYO