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CCSi TechNotes: Basics of Rockwell Hardness Testing
In Rockwell testing, hardness is determined by measuring the comparative depth of two carefully controlled indentations, one superimposed over the other.
First a Minor Load (one of a lesser force) is applied to a steel ball or sphero—conical diamond penetrator. Then, while the Minor Load is still being applied, a Major Load (one of greater force) is applied at a precisely controlled rate. The Major Load is removed and the hardness determination is displayed.
The hardness determination obtained represents the additional depth to which the Major Load has indented the test specimen beyond the initial indentation of the application of the Minor Load. The displayed indication is proportionally inverse, e.g. the higher the displayed determination of hardness, the shallower the indentations, therefore the harder the material.
In the regular (R) Rockwell scale, the Minor Load is is 10 kgf and the Major Load may be 60, 100, or 150 kgf. In the superficial scale (S), the Minor Load is 3 kgf and the Major Load may be 15, 30, or 45 kgf.
To ensure accuracy and consistency, the Major Load is under precise control and the penetrators are manufactured to specific tolerances. Each point of hardness on the regular (R) scale is 0.00008 inch and 0.00004 inch on the superficial (S) scale, making the need for precise control of the applied forces and precision manufacture of the penetrators readily apparent.
Minor v. Major Load Indentations
Rockwell Regular Scales
ROCKWELL (R) REGULAR SCALE APPLICATIONS
Scale
Symbol
Penetrator Major (Minor)
Load
Typical Application
A Brale 60 kgf (10 kgf) · cemented carbides
· thin steel
· shallow case hardened steel
B 1/16" Ball 100 kgf (10 kgf) · cooper alloys
· soft steel
· aluminium alloys
· malleable iron
C Brale 150 kgf (10 kgf) · steel
· hard cast iron
· perlitic malleable iron
· titanium
· deep case hardened steel
D Brale 100 kgf (10 kgf) · thin steel
· medium case hardened steel
· perlitic malleable iron
E 1/8" Ball 100 kgf (10 kgf) · cast iron
· aluminium alloys
· magnesium alloys
· bearing metals
F 1/16" Ball 60 kgf (10 kgf) · annealed copper alloys
· thin soft sheet metal
G 1/16" Ball 150 kgf (10 kgf) · phosphor bronze
· beryllium
· cooper
· malleable iron
(G92+ will damage penetrator)
H 1/8" Ball 60 kgf (10 kgf) · zinc
· lead
· aluminum
K 1/8" Ball 150 kgf (10 kgf) · bearing metals
· relatively soft
· thin materials
· plastics (refer to ASTM D7851)

Use the smallest ball and highest force that do not give "anvil" effect
L 1/4" Ball 60 kgf (10 kgf)
M 1/4" Ball 100 kgf (10 kgf)
P 1/4" Ball 150 kgf (10 kgf)
R 1/2" Ball 60 kgf (10 kgf)
S 1/2" Ball 100 kgf (10 kgf)
V 1/2" Ball 150 kgf (10 kgf)
1 ASTM D785 (Vol. 08.01) Standard Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials
Rockwell Superficial Scales
ROCKWELL (S) SUPERFICIAL SCALE APPLICATIONS
Scale
Symbol
Penetrator Major (Minor)
Load
Typical Application
15N Brale 15 kgf (3 kgf) Superficial scale is ideal for testing materials that do not have sufficient width or thickness to be tested on the Regular (R) Rockwell Hardness Scale, these are typically:
· very thin sheet metal
· strip metal
· wire
· small rounds
· nitrided steel
· lightly carburized steel
· heavily cyanided steel
· tin plate
· other similarly configured specimens or materials.
30N Brale 30 kgf (3 kgf)
45N Brale 45 kgf (3 kgf)
15T 1/16" Ball 15 kgf (3 kgf)
30T 1/16" Ball 30 kgf (3 kgf)
45T 1/16" Ball 45 kgf (3 kgf)
15W 1/8" Ball 15 kgf (3 kgf)
30W 1/8" Ball 30 kgf (3 kgf)
45W 1/8" Ball 45 kgf (3 kgf)
15X 1/4" Ball 15 kgf (3 kgf)
30X 1/4" Ball 30 kgf (3 kgf)
45X 1/4" Ball 45 kgf (3 kgf)
15Y 1/2" Ball 15 kgf (3 kgf)
30Y 1/2" Ball 30 kgf (3 kgf)
45Y 1/2" Ball 45 kgf (3 kgf)
Rockwell Carbide Scales
Scale C (carbide) testers are used for testing cemented carbides in the Rockwell A Scale, where tolerances of ± 0.20 of a Rockwell Hardness point are required. A specially selected "A" Brale penetrator is used to measure the hardness of cemented carbides in accordance with ASTM B 294 and the Cemented Carbide Producer's Association (CCPA).
In addition to the 60 kgf Major Load required for carbide A Scale testing, the Scale C testers also include 100 and 150 kgf capabilities.

Copyright © 2006 CCSi, Inc. • All Rights Reserved • Published February, 2006
Corporate Consulting, Service & Instruments, Incorporated
221 Beaver Street • Akron, Ohio 44304 USA
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