ASTM B692-18(2023)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B692 − 18 (Reapproved 2023)
Standard Specification for
75 % Silver-25 % Graphite Sliding Contact Material
This standard is issued under the fixed designation B692; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 NEMA Standard:
CB-1 Brushes for Electrical Machines
1.1 This specification defines the criteria for composition
and other requirements for brushes with a nominal silver
3. Requirements
content of 75 weight % with the balance being substantially
graphite.
3.1 Chemical Composition shall be as follows:
Silver 75 ± 3 % (weight)
1.2 The values stated in inch-pound units are to be regarded
Graphite balance
as standard. The values given in parentheses are mathematical
Total metal impurities 1 % max
Percent ash in graphite (NEMA CB-1) 5 % max
conversions to SI units that are provided for information only
and are not considered standard.
3.2 Physical Properties—The following lot average proper-
ties must be met. Unless otherwise agreed between the pro-
1.3 This standard does not purport to address all of the
ducer and the user, the number of samples shall be five.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to become familiar
3.2.1 Density—The minimum acceptable density shall be
with all hazards including those identified in the appropriate 4.6 g/cm as determined by the measurement and weight
Safety Data Sheet (SDS) for this product/material as provided method defined by NEMA CB-1.
by the manufacturer, to establish appropriate safety, health,
3.2.2 Shear Strength:
and environmental practices, and determine the applicability
3.2.2.1 The shear strength for the normal and transverse
of regulatory limitations prior to use.
directions shall be measured for rectangular parallelepipeds
1.4 This international standard was developed in accor-
and shall be 2000 psi (14 MPa), minimum.
dance with internationally recognized principles on standard-
3.2.2.2 The shear strength for the longitudinal shear direc-
ization established in the Decision on Principles for the
tion shall be measured for cylinders and shall be 1000 psi
Development of International Standards, Guides and Recom-
(6.9 MPa), minimum.
mendations issued by the World Trade Organization Technical
3.3 Microstructure—Parts shall be visually free of structural
Barriers to Trade (TBT) Committee.
defects, cracks, etc., upon examination at 50×. The press
2. Referenced Documents direction, as evidenced by laminations, shall be as defined by
the purchase order. Also the brush material shall not contain
2.1 ASTM Standards:
abrasive particles that will sliver a metal-alloy ring with a
B613 Guide for Preparing Specifications for Miniature
hardness ≥110 HK when the brush force is equal to 30 g or
Brushes of Composite Materials for Sliding Electric
that necessary for 5.0 psi (34 kPa) pressure, whichever is
Contacts
greater. A sliver is defined as a loose wear particle with one
E18 Test Methods for Rockwell Hardness of Metallic Ma-
dimension ≥50× t
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