ASME B1.1:2003 pdf download Unified Inch Screw Threads (UN and UNR Thread Form)
GENERAL
1.1 Scope
This Standard specifies the thread form, series, classallowance, tolerance, and designation for unified screwthreads.(In order to emphasize that unified screwthreads are based on inch modules, they mav be denotedunified inch screw threads.) Several variations in threadform have been developed for unified threads; howeverthis Standard covers only UN and UNR thread formsFor easy reference. a metric translation of this Standard has been incorporated as Nonmandatory Appendix C. Nonmandatory Appendices A through E containuseful information that is supplementary to the sectionsof this Standard.
1.2 Unified Screw Thread Standards
The standards for unified screw threads published inthis Standard are in agreement with formal standardsof the International Organization for Standardizationfor diameter-pitch combinations, designations, and tol!erances for 60 deg triangular form inch screw threadsUnified screw threads had their origin in an accordsigned in Washington, D.C., on November 18, 1948, byrepresentatives of standardizing bodies of Canada, theUnited Kingdom, and the United States, and have subsequently superseded American National screw threads.
1.3 UN and UNR Screw Threads
UNR applies only to external threads; the differencebetween UN and UNR threads, in addition to designation, is that a flat or optional rounded root contour isspecified for UN threads, while only a rounded rootcontour is specified for UNR threads.
1.4 Interchangeability
Unified (UN/UNR) and its predecessor,AmericanNational screw threads, have substantially the samethread form, and threads of both standards having thesame diameter and pitch are mechanically interchangeable. The principal differences between these standardsrelate to the application of allowances, the variation oftolerances with size, differences in the amounts of pitchdiameter tolerances for external and internal threads.and differences in thread designations. Unified inch and ISO metric screw threads are not mechanically inter-changeable.
1.5 Designations
Unified thread sizes (specific combinations of diameter and pitch) are identified by the letter combination“UN” in the thread symbol. In the unified standards,the pitch diameter tolerances for external threads differfrom those for internal threads; for this reason the letterA” is used in the thread symbol to denote an externalthread and the letter “B,” an internal thread. Where theletters“U”“A” or “B” do not appear in the threaddesignation, the threads conform to the outdated Ameri-can National screw threads. Details regarding threaddesignations are given in para. 6.
1.6 Reference Documents
The latest issues of the following documents form apart of this Standard to the extent specified herein.When the following American National Standardsreferred to in this Standard are superseded by a revisionapproved by the American National Standards InstituteInc., the revision should apply.
ASME B1.2, Gages and Gaging for Unified Inch ScrewThreads
ASME B1.3, Screw Thread Gaging Systems for Dimen-sional Acceptability – Inch and Metric Screw ThreadsASME B1.7,Nomenclature, Definitions, and Letter Sym-bols for Screw Threads
ASME B1.30,Screw Threads – Standard Practices forCalculating and Rounding Dimensions
ASME B47.1,Gage Blanks
ASME B94.11Twist Drills
ASME Y14.5,Dimensioning and Tolerancing
Publisher: The American Society of Mechanical Engi-neers (ASME International), Three Park Avenue NewYork，NY 10016-5990; Order Department: 22 LawDrive，Box 2300,Fairfield,NJ 07007-2300
ISO 68, General Purpose Screw Threads — Basic ProfilePublisher: International Organization for Standardization (ISO),1 rue de Varembe, Case Postale 56，CH1211, Geneve 20,Switzerland/Suisse