Rockwell Hardness Tester
|Serial Number||4MM 344|
|Arrival Date||Summer, 2015|
|Contact||Host Cold Metals|
|Where||Cold Metals, on a bench|
|Host Area||Cold Metals|
The Rockwell scale is a hardness scale based on indentation 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.
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.
- 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.)
- Axe: 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.
Copied from wikipedia
The indentors and hardness test blocks and spare anvils are in the tan cabinet, fifth drawer down.
Indentor / Penitrator Choice
Diamond indentor, marked 'MC' for hard materials RHC scale ( see wikipedia for scale explanation) Ball indentor for RHB scale.
1. Select the penetrator/indentor.
Soft materials are usually tested in the Rockwell B Scale, using 1/16″ ball penetrator and 100 Kg Major Load. Hardened steel and hard alloys are tested in the Rockwell C Scale, using a diamond penetrator and a 150 Kg Major Load. Do not use the ball penetrator with the steel test block or when testing hard steel. Such a procedure will damage the penetrator and result in invalid tests
2. Set up the tester
Secure the penetrator/indentor and the appropriate anvil in the tester. Select correct weight, 150kg for C scale 100 kg for B scale. Three weights are stacked in the tester, the bottom is 60kg, next is 40kg then 50kg. With all three weights the total is 150kg, for the C scale. Remove the top weight and you have 100 kg for the B scale.
3. Apply Minor Load
Slowly turn the hand wheel to bring the small dial indicator hand to the line. This applies a minor pressure load to the penetrator.
4. Apply Major Load
Turn the major load lever back to apply major load.
5. Release major load
Turn the major load lever forward to release major load.
6. Take the reading
With the diamond penetrator, read Column C on the barrel dial (black numbers). With the ball penetrator, read column B (red numbers). NOTE: The first two or three tests may be low until the penetrator and anvil have become firmly seated.
Test samples in the drawer are marked with hardness.
Keep the dust cover on. Use calibration discs if you care about your results. Accessories for the tester are in the tan colored cabinet.
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