ASME B1-21M:1997 pdf download METRIC SCREW THREADSII MJPROFllE
1.1 Scope
This Standard establishes the basic triangular profilefor the MJ thread form; provides a system of designations; lists the standard series of diameter/pitch combina-tions for diameters from 1.6 to 200 mm; and specifieslimiting dimensions and tolerances.
It specifies the characteristics of the MJ metric seriesof threads having a minimum 0.15011P radius at theroot of the external thread, and also having the minordiameter of the external and intermal threads increasedabove the ASME B1.13M thread form to accommodatethe external thread root radius.
1.2 Field of Application
The MJ screw thread is designed for use on highlystressed applications requiring high fatigue strengthFor aerospace applications, except for fuid fittings,Tolerance Classes 4H5H or 4G6G and 4h6h should beused. These classes approximate Classes 3B/3A in theinch system. Aerospace fluid fittings use Classes 4H5Hor 4H6H and 4g6g.
Tolerance Classes 4G5G or 4G6G and 4g6g areprovided for use when thread allowances are required.These classes result in a slightly tighter fit than theinch Classes 2B/2A at minimum material condition.Additional Tolerance Classes 6H/6g are included inthis Standard to provide appropriate product selectionbased on general applications. These classes and theselection of standard diameter/pitch combinations arethe same as those provided for the M profile metricscrew threads in ASME B113M. Classes 6H/6g resultin a slightly looser fit than inch Classes 2B/2A atminimum material condition.
1.3 Assembly
Threads conforming to the M profile (ASME BI.13M)and the MJ profile are not interchangeable because ofpossible interference between the MJ external threadminor diameter and the Bl.13M internal thread minor diameter. However, the MJ internal thread will assemblewith the Bl.13M exteral thread.
1.4 Federal Government Use
When this Standard is approved by the Departmentof Defense and Federal Agencies and is incorporatedinto FED-STD-H28/21. Screw Thread Standards forFederal Services, Section 2l, the use of this Standardby the Federal Government is subject to all the require.ments and limitations of FED-STD-H28/21.
1.5 References
The latest issucs of the following documents forma part of this Standard to the extent specified herein.American National Standards
ASME Bl.3M，Screw Thread Gaging Systems forDimensional Acceptability — Inch and Metric ScrewThreads (UN，UNR，UNJ，M、and MJ)ANSIASME B1.7M，Nomenclature，Dcfinitions，andLetter Symbols for Screw ThreadsASME B1.10M，Unified Miniature Screw ThreadsASME B1.13M，Metric Screw Threads — M ProfleASME Bl.15,Unified Inch Screw Threads (UNJ Thread
Form)
ANSVASME B1.22M，Gages and Gaging Practice forMJ Series Metric Screw ThreadsASME B1.30MScrew Threads — Standard Practicefor Calculating and Rounding Dimensions
ISO Standards
ISO 26l, ISO General Purpose Metric Screw Threads 一General PlanISO 965-1，ISO General Purpose Metric ScrewThreads – Part 1 Principles and Basic Data
ISO 5855-1-2-3，Aerospace MJ Threads
2 PROFILE OF THREAD
2.1 Basic Profile
The basic profile is the theoretical profile correspond-ing to the basic dimensions of the thread major diameter.
ASME B1-21M:1997 pdf download
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