|
What
does "traceable to NIST" really mean?
IP Rating for Caliper and
Micrometers
Gage Block Grades- New and Old Standards
They are available in various grades depending on their intended use.
- reference (AAA): small
tolerance (± 0.00005 in or 0.000002 in) used to establish standards
- calibration (AA): (tolerance +0.000004" to
-0.000002") used to calibrate inspection blocks and very high precision
gauging
- inspection (A): (tolerance +0.000006" to -0.00002")
used as
toolroom standards for setting other gauging tools
- workshop (B): large tolerance (tolerance +0..000009"
to -0.000005" ) used as shop standards for precision measurement
More recent grade designations include (U.S. Federal Specification
GGG-G-15C):
- 0.5 — generally equivalent to grade AAA
- 1 — generally equivalent to grade AA
- 2 — generally equivalent to grade A+
- 3 — compromise grade between A and B
The newest gage block grading system, ANSI/ASME B89.1.9-2002, which defines both absolute deviations from nominal
dimensions and parallelism limits as criteria for grade determination.
Generally, grades are equivalent to former U.S. Federal grades as follows:
- 00 — generally equivalent to grade 1 (most exacting
flatness and accuracy requirements)
- 0 — generally equivalent to grade 2
- AS-1 — generally equivalent to grade 3 (reportedly
stands for American Standard - 1)
- AS-2 — generally less accurate than grade 3
- K — generally equivalent to grade 00 flatness
(parallelism) with grade AS-1 accuracy
The ANSI/ASME standard follows a similar philosophy as set forth in
ISO 3650.
ASME B89.1.9-2002 for suggested gage block
replacement:
|
Regulation |
Grade |
|
OLD GGG |
AAA |
AA |
A |
B |
|
|
GGG-G-15C |
0.5 |
1 |
2 |
3 |
3 |
|
B89.1.9-2002 |
N/A |
00 |
0 |
AS-1 |
AS-2 |
|
81 PC. GAGE BLOCK SETS |
|
9 BLOCKS: .1001” - .1009” (.0001” STEPS) |
|
49 BLOCKS: .101”-.149” (.001” STEPS) |
|
19 BLOCKS: .050” - .950” (.050” STEPS) |
|
4 BLOCKS: 1.000”- 4.000” (1.000” STEPS) |
|
|
|
|
|
36 PC. GAGE BLOCK SETS |
|
1 BLOCK: .050” |
|
9 BLOCKS: .1001” - .1009” (.0001” STEPS) |
|
9 BLOCKS: .101” - .109” (.001” STEPS) |
|
9 BLOCKS: .110” - .190” (.010” STEPS) |
|
5 BLOCKS: .100” - .500” (.100” STEPS) |
|
3 BLOCKS: 1.0”, 2.0”, 4.0” |
|
|
|
|
|
47 PC METRIC GAGE BLOCK SETS |
|
1 BLOCK: 1.005 |
|
20 BLOCKS: 1.01 - 1.20 (.01MM STEPS) |
|
7 BLOCKS: 1.3 -1.9 (.1MM STEPS) |
|
9 BLOCKS: 1.0-9.0 (1MM STEPS) |
|
10 BLOCKS: 10.0-100.0 (10MM STEPS) |
|
|
|
|
|
87 PC METRIC GAGE BLOCK SETS |
|
9 BLOCKS: 1.001-1.009 (.001MM STEPS) |
|
49 BLOCKS: 1.01 - 1.49 (.01MM STEPS) |
|
19 BLOCKS: 0.5 - 9.5 (0.5MM STEPS) |
|
10 BLOCKS: 10.0 - 100.0 (10MM STEPS) |
|
B89.1.9 |
Grade 00 |
Grade 0 |
Grade AS-1 |
Grade AS-2 |
|
Size |
Tolerance |
Tolerance |
Tolerance |
Tolerance |
|
Thru .050" |
+4/-4 |
+6/-6 |
+12/-12 |
+24/-24 |
|
Thru .400" |
+3/-3 |
+5/-5 |
+8/-8 |
+18/-18 |
|
Thru 1" |
+3/-3 |
+6/-6 |
+12/-12 |
+24/-24 |
|
Thru 2" |
+4/-4 |
+8/-8 |
+16/-16 |
+32/-32 |
|
Thru 3" |
+5/-5 |
+10/-10 |
+20/-20 |
+40/-40 |
|
Thru 4" |
+6/-6 |
+12/-12 |
+24/-24 |
+48/-48 |
|
Thru 5" |
+8/-8 |
+16/-16 |
+32/-32 |
+64/-64 |
|
Thru 6" |
+8/-8 |
+16/-16 |
+32/-32 |
+64/-64 |
|
Thru 7" |
+10/-10 |
+20/-20 |
+40/-40 |
+80/-80 |
|
Thru 8" |
+10/-10 |
+20/-20 |
+40/-40 |
+80/-80 |
|
Thru 10" |
+12/-12 |
+24/-24 |
+48/-48 |
+104/-104 |
|
Thru 12" |
+14/-14 |
+28/-28 |
+56/-56 |
+112/-112 |
|
Thru 16" |
+18/-18 |
+36/-36 |
+72/-72 |
+144/-144 |
|
Thru 20" |
+20/-20 |
+44/-44 |
+88/-88 |
+176/-176 |
|
Inch system: Tolerances expressed in micro inches
(.000001") 1 millionth of an inch |
|
Quality Magazine,
December 2010 Issue
Quality 101: Traceable
to NIST, Explained
by Rich
Rhoney
December 2, 2010
The term NIST traceable is deciphered.
Many gage calibration and repair facilities often find themselves
discussing the topic of National Institute of Standards and
Technology (NIST) traceability with customers going though ISO
audits. Confirming or tracking NIST gage traceability are concepts
with which more ISO accredited manufacturers should familiarize
themselves.
Most manufacturers have seen the statements on calibration
certificates that read, “All measurements are traceable to NIST,”
when they purchase a micrometer, caliper or gage block set. But many
of them still question what the word traceable really means.
The definition of traceability that has achieved global acceptance
in the metrology community is contained in the International
Vocabulary of Metrology (VIM) as “property of a measurement result
whereby the result can be related to a reference through a
documented unbroken chain of calibrations, each contributing to the
measurement uncertainty.”
Identifying Traceability
It is important to note that traceability is the property of the
result of a measurement, not of an instrument or calibration report
or laboratory. It is not achieved by following any one particular
procedure or using special equipment.
Merely having an instrument calibrated, even by NIST, is not enough
to make the measurement result obtained from that instrument
traceable to realizations of the appropriate International System of
Units (SI) or other specified references. The measurement system by
which values and uncertainties are transferred must be clearly
understood and under control.
The VIM definition states that metrological traceability is a
property of a measurement results by which that result is related to
specified reference standards, not to institutions. Accordingly, the
phrase “traceable to NIST,” in its most proper sense, is shorthand
for metrologically traceable to NIST’s practical realization of the
definition of a measurement unit.
Referencing the NIST
Number
Many imported gage certificates will state that equipment used for
inspection is directly traceable to NIST and then a NIST test number
will follow. Having a NIST test number is only a reference number
for tracking internal documents at NIST. But how does one know its
specific application?
Again, the NIST definition for test numbers helps explain.
“Test report numbers issued by NIST are intended to be used solely
for administrative purposes,” NIST says. “Although they are often
used to uniquely identify documents which bear evidence of
traceability, test report numbers themselves do not address the
issue and should not be used nor required as the sole proof of
traceability.”
When reading that statement, one should contact the manufacturer of
the gage he is using and ask what instruments or measurements the
manufacturer is referring to.
As the operator of that instrument, one must provide proof of an
unbroken chain of traceability if an ISO auditor asks for that
information, and an ISO/IEC 17025: 2005 accredited laboratory is
required to prove that its processes and procedures are traceable to
NIST. The above procedures make that possible
|
Rich
Rhoney
Rich Rhoney is general manager at Gage
Services Inc. (Novi, MI). For more information, visit.
www.gageservices.com
IP Ratings for Calipers and
Micrometers
The IP rating normally has two (or three) numbers:
- Protection from solid objects or materials
- Protection from liquids (water)
- Protection against mechanical impacts (commonly omitted, the third
number is not a part of IEC 60529)
Example - IP Rating
With the IP rating IP 54, 5 describes the level of protection from solid
objects and 4 describes the level of protection from liquids.
An "X" can used for one of the digits if there is only one class of
protection, i.e. IPX1 which addresses protection against vertically falling
drops of water e.g. condensation..
IP First number - Protection against solid objects
| 0 |
No special protection |
| 1 |
Protected against solid objects up to 50 mm, e.g. accidental
touch by persons hands. |
| 2 |
Protected against solid objects up to 12 mm, e.g. persons
fingers. |
| 3 |
Protected against solid objects over 2.5 mm (tools and wires). |
| 4 |
Protected against solid objects over 1 mm (tools, wires, and
small wires). |
| 5 |
Protected against dust limited ingress (no harmful deposit). |
| 6 |
Totally protected against dust. |
IP Second number - Protection against liquids
| 0 |
No protection. |
| 1 |
Protection against vertically falling drops of water e.g.
condensation. |
| 2 |
Protection against direct sprays of water up to 15o
from the vertical. |
| 3 |
Protected against direct sprays of water up to 60o
from the vertical. |
| 4 |
Protection against water sprayed from all directions - limited
ingress permitted. |
| 5 |
Protected against low pressure jets of water from all directions
- limited ingress. |
| 6 |
Protected against temporary flooding of water, e.g. for use on
ship decks - limited ingress permitted. |
| 7 |
Protected against the effect of immersion between 15 cm and 1 m. |
| 8 |
Protects against long periods of immersion under pressure. |
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