ANSI/ASME B1.1:2003 Pitch Diameter Changes for 1A
and 1B
Summary
In 2003 the ASME B1 Committee finalized changes
to ANSI B1.1. This page only talks about pitch
diameter changes. Many of the tabulated screw thread pitch diameter
sizes remained the same. The tabulated screw thread pitch diameters
which changed only moved 0.0001 to 0.0002 of an inch. This small
amount of change is considered insignificant to fit and function
of the threaded assembly, but important enough to change to help
assure consistency in the future.
There were no changes for:
Internal 1B minimum pitch diameter
External 1B maximum pitch diameter
Internal 2B minimum pitch diameter
External 3A maximum pitch diameter
Internal 3B minimum pitch diameter
Changes to 1A and 1B:
The data which remained unchanged is not contained in this chart.
Screw Thread Size
1A
GO
NOGO
2003
1989
2003
1989
7/16"-20 UNF
…
…
0.3974
0.3975
5/8"-11 UNC
0.5643
0.5644
0.5560
0.5561
Other Changes:
This page only speaks to ANSI/ASME B1.1:2003 pitch diameter changes
because the screw thread pitch diameter is a very visible screw
thread size component. Other features of the screw thread did also
change, again to an insignificant degree. The complete list of changes
are outlined in the appendix to ANSI/ASME B1.1:2003.
The Goal:
The The intent of the authors of the standard is that the world
move to the newest version of the standard with all possible haste.
It is understood that disputes will arise over minutia, but the
authors seem to indicate that the minutia is insignificant to the
fit and function of the end product. The parties involved in any
dispute related to these changes to this standard should resolve
it with an eye toward fit and function in existing parts; flexibility
of designs to absorb changes in the standard; and minimal cost consequences
for all parties involved. It is known that many prints contain pitch
diameter or other data related to thread information, which was
in agreement with the older version of the standard, but now is
in conflict with the new version of the standard. That old data
should be revised, or deviated to meet the new standard requirements
in all cases.
This data is provided for general information only. The intention
is to provide accurate information; regardless; errors may exist
in the supplied information. If accuracy is critical, base your
final decisions on the data provided in the root document: ANSI/ASME
B1.1:2003. ANSI/ASME B1.1:2003 is a copyrighted document. To
purchase a copy visit an Authorized
Reseller.
Original Posting: 6/15/2010
Last Revision:
Error corrections in, or comments about, the above data can be sent
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