Rockwell Hardness Tester

Rockwell Hardness Tester

Owner/Loaner	PS:One
Serial Number	4MM 344
Make/Model	4M
Arrival Date	Summer, 2015
Usability	yes
Contact	Host Cold Metals
Where	Cold Metals, on a bench
Authorization Needed	yes
Hackable	no
Estimated Value	$500
Host Area	Cold Metals

Qualified Member	Trained By
NA	Danger committee

Rockwell Hardness

The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale. When testing metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers.

Copied from Wikipedia. See Wikipedia for additional background

Scales and values

There are several alternative scales, the most commonly used being the "B" and "C" scales. Both express hardness as an arbitrary dimensionless number.

Various Rockwell scales

Scale	Abbreviation	Load	Indenter	Use	N	s
A	HRA	60 kgf	120° diamond spheroconical†	Tungsten carbide	100	0.002mm
B	HRB	100 kgf	Template:Convert steel sphere	Aluminium, brass, and soft steels	130	0.002mm
C	HRC	150 kgf	120° diamond spheroconical	Harder steels >B100	100	0.002mm
D	HRD	100 kgf	120° diamond spheroconical		100	0.002mm
E	HRE	100 kgf	Template:Convert steel sphere		130	0.002mm
F	HRF	60 kgf	Template:Convert steel sphere		130	0.002mm
G	HRG	150 kgf	Template:Convert steel sphere		130	0.002mm
†Also called a brale indenter

• Except for testing thin materials in accordance with A623, the steel indenter balls have been replaced by tungsten carbide balls of the varying diameters. When a ball indenter is used, the letter "W" is used to indicate a tungsten carbide ball was used, and the letter "S" indicates the use of a steel ball. E.g.: 70 HRBW indicates the reading was 70 in the Rockwell B scale using a tungsten carbide indenter.

The superficial Rockwell scales use lower loads and shallower impressions on brittle and very thin materials. The 45N scale employs a 45-kgf load on a diamond cone-shaped Brale indenter, and can be used on dense ceramics. The 15T scale employs a 15-kgf load on a Template:Convert hardened steel ball, and can be used on sheet metal.

The B and C scales overlap, such that readings below HRC 20 and those above HRB 100, generally considered unreliable, need not be taken or specified.

Typical values

• Very hard steel (e.g. chisels, quality knife blades): HRC 55–66 (Hardened High Speed Carbon and Tool Steels such as M2, W2, O1, CPM-M4, and D2, as well as many of the newer powder metallurgy Stainless Steels such as S30V, CPMS-154, ZDP-189, etc.)
• Axes: about HRC 45–55
• Brass: HRB 55 (Low brass, UNS C24000, H01 Temper) to HRB 93 (Cartridge Brass, UNS C26000 (260 Brass), H10 Temper)

Several other scales, including the extensive A-scale, are used for specialized applications. There are special scales for measuring case-hardened specimens.

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Operation

Select the correct indentor - diamond for HRC other material for HRC ( what is an indentor? need identification and use of indentors in stock)

1) Install indentor  (photo ?)
2) Support load (how?)
3) Place component on anvil, use a specialized anvil if needed ( eg. round stock)
4) Turn handwheel to apply the 'minor load' until needle points to indicator mark on dial.  ( id handwheel photo?)
5) Zero out dial.
6) Depress lever to apply 'major load' , allow time to settle.  (where is lever? what is depress? move forward?)
7) Release lever
8) Read dial for hardness.  (photo example how?)

Testing

Test samples explained.

Notes

As of October 2015, the machine shop doesn't have a diamond indenter for the Rockwell C scale -- but we do have spherical indenters for Rockwell B.

Keep the dust cover on. Use calibration discs if you care about your results. Accessories for the tester are in the tan colored cabinet.

Resources

Wikipedia : https://en.wikipedia.org/wiki/Rockwell_scale

This video shows another machine but it has a good explanation of the test: https://www.youtube.com/watch?v=G2JGNlIvNC4

Again a different machine but shows procedure : https://www.youtube.com/watch?v=3FX3wFhk0mQ

Source for diamond indentor: http://www.westportcorp.com/dpc1.html