Outlined below are the recommended methods of
inspection of a Retaining Ring with explanations of the terms
of measurement used by our engineers and inspectors. Also listed
are the measuring devices best suited for accurate determination
of the specifications to be met. Wherever possible we advise that
any measurements necessary, be taken when the ring is in the assembled
state or a simulation of these conditions. If this is not possible,
the catalog supplies the critical free dimensions and applicable
tolerances. Note: Non critical dimensions are not listed but are
available upon request.
Gap Calculation
Diameter of the ring and its relationship
to the distance between the gap ends should be considered first.
The factor pi times any increment of diameter variance is directly
proportional to gap variance.
More simply stated, if the free diameter in
a ring varies a given amount, the free gap dimension will vary
by pi times this amount. To clarify as much as possible, most
catalog ring listings carry a free gap minimum and maximum dimension
which eliminates the necessity of calculation to ascertain correct
gap measurement. Only in minor measurement areas is a minimum
or reference dimension shown.
Methods of Inspection
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Internal Diameter
- Measure with Vernier Caliper or plug gauge with go or no go
diameters. |
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Outer Diameter -
Measure with Vernier Caliper or O.D. gauge with go or no go diameters. |
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Gap - Or distance
between points is measured, preferably at installed diameter,
with Vernier Caliper. If in the free state use a Vernier Caliper
to the minimum maximum dimensions specified, or calculate the
allowed gap as previously explained. |
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Gap Angle - Measured
off radial line from center of Ring I.D. |
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Width of wire section - Refers to the radial
measurement as shown, using a point micrometer or Vernier Caliper.
Thickness is measured with a micrometer and is the axial distance
between the flat planes as shown.
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Axial Clearance Table
*Helix, dish, and axial kink combined are measured by placing
the ring between parallel plates under a 10 lb. load. Using a
feeler gauge and checking the allowable clearance between plates
according to the following table gives accurate and quick results.
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Ring Thickness
.029"/.033"
.040"/.044"
.045"/.049"
.060"/.064"
.076"/.080"
.091"/.097"
.106"/.112"
.121"/.129"
.138"/.144"
.152"/.158"
.182"/.190"
.245"/.255"
.306"/.318"
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Max. Clearance
Under Load
.038
.051
.056
.074
.092
.112
.129
.149
.166
.182
.216
.287
.354
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 Radial Kink
This is also known as out of round
or radial deformation. This occurs when the periphery of the ring
does not follow the radius in a continuous plane. Measurement
is secured by using a feeler gauge to check the distance between
the ring and periphery when assembled in an I.D. or O.D. gauge.
Hardness Testing
Specified hardness is generally checked
by using a penetration test, after a Parallel grind. Rockwell
C scale readings are used throughout our production facilities.
When it is not possible to use a penetration test a tensile strength
test is performed and the results converted to a Rockwell reading.
Ring Performance
Check for function and suitability
of the retaining rings in regards to uniformity of temper and
wire cross-section:
External Rings
After having been expanded to pass over the maximum shaft diameter
"S", ring must return to a free diameter less than
minimum specified groove diameter "C" to ensure rings
are not loose in groove.
Internal Rings
After having been compressed to pass through minimum bore diameter
"S", rings must expand outward to a free diameter in
excess of the maximum specified groove diameter "C",
to ensure that rings are not loose in groove.
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