government recognized export house | ohsas 18001:2007...

A N A M E R I C A N N A T I O N A L S T A N D A R D

Unified Inch Screw Threads(UN and UNR Thread Form)

ASME B1.1-2003[Revision of ASME B1.1-1989 (R2001)]

http://www.bzxzw.com

A N A M E R I C A N N A T I O N A L S T A N D A R D

UNIFIED INCHSCREW THREADS

(UN and UNR Thread Form)

ASME B1.1-2003[Revision of ASME B1.1-1989 (R2001)]

标准下载网(www.bzxzw.com)


Date of Issuance: September 30, 2004

The 2004 edition of this Standard is being issued with an automatic addenda subscription service.The use of addenda allows revisions made in response to public review comments or committeeactions to be published as necessary. This Standard will be revised when the Society approves theissuance of a new edition.

There will be no written interpretations of the requirements of this Standard issued to this edition.

ASME is the registered trademark of The American Society of Mechanical Engineers.

This code or standard was developed under procedures accredited as meeting the criteria for American NationalStandards. The Standards Committee that approved the code or standard was balanced to assure that individuals fromcompetent and concerned interests have had an opportunity to participate. The proposed code or standard was madeavailable for public review and comment that provides an opportunity for additional public input from industry, academia,regulatory agencies, and the public-at-large.

ASME does not “approve,” “rate,” or “endorse” any item, construction, proprietary device, or activity.ASME does not take any position with respect to the validity of any patent rights asserted in connection with any

items mentioned in this document, and does not undertake to insure anyone utilizing a standard against liability forinfringement of any applicable letters patent, nor assume any such liability. Users of a code or standard are expresslyadvised that determination of the validity of any such patent rights, and the risk of infringement of such rights, isentirely their own responsibility.

Participation by federal agency representative(s) or person(s) affiliated with industry is not to be interpreted asgovernment or industry endorsement of this code or standard.

ASME accepts responsibility for only those interpretations of this document issued in accordance with the establishedASME procedures and policies, which precludes the issuance of interpretations by individuals.

No part of this document may be reproduced in any form,in an electronic retrieval system or otherwise,

without the prior written permission of the publisher.

The American Society of Mechanical EngineersThree Park Avenue, New York, NY 10016-5990

Copyright © 2004 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERS

All rights reservedPrinted in U.S.A.

CONTENTS

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viCommittee Roster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Unified Screw Thread Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 UN and UNR Screw Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Interchangeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6 Reference Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7 Acceptability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.8 Reference Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.9 Units of Measure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.10 Federal Government Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Screw Thread Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 Basic Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3 Design Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4 Formulas and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3 Screw Thread Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1 Thread Series Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2 Order of Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3 Coarse-Thread Series Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.4 Fine-Thread Series Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.5 Extra-Fine-Thread Series Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.6 Constant-Pitch Thread Series Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.7 Fine Threads for Thin-Wall Tubing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4 Screw Thread Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364.1 Thread Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364.2 Combinations of Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5 Screw Thread Allowance and Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.1 Allowance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.2 Pitch Diameter Tolerance, All Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.3 Special Lengths of Engagement, LE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375.4 Minor Diameter Tolerance and Allowance for External Threads . . . . . . . . . . 545.5 Major Diameter Tolerance for Internal Threads . . . . . . . . . . . . . . . . . . . . . . . . . . 545.6 Minor Diameter Tolerance and Length of Engagement for Internal

Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555.7 Disposition of Allowance and Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555.8 Formulas for Allowance and Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555.9 Lead and Flank Angle Tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585.10 Coated or Plated Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585.11 Circular Runout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

6 Screw Thread Designation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586.1 Basic Method of Designating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

iii



6.2 Method of Designating Coated Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616.3 Method of Designating Left-Hand Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626.4 Method of Designating UNS Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626.5 Designations for Other Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626.6 Method of Designating Threads Having Special Length of

Engagement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636.7 Method of Designating Threads Having Modified Crests. . . . . . . . . . . . . . . . . 63

7 Dimensional Accommodation of Coating or Plating for 60-deg Threads . . . . . . . . . . 647.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647.2 Material Lifts for Coated Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647.3 Dimensional Effects of Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647.4 External Thread With Allowance Available for Coating . . . . . . . . . . . . . . . . . . 647.5 External Thread With No Allowance for Coating . . . . . . . . . . . . . . . . . . . . . . . . 647.6 Internal Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667.7 Electrodeposited Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677.8 Other Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8 Standard Series Threads (UN/UNR) and Limits of Size for Standard Seriesand UNS/UNRS Series Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8.1 Standard Series. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 678.2 Limits of Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 678.3 Formulas for Limits of Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 678.4 Example of Calculations From Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

9 Lead and Angle Tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 689.1 Lead and Flank Angle Acceptance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

10 Formulas and Symbols for Thread Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6910.1 Thread Form Formulas and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

11 Tables of Basic Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7011.1 Table Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7011.2 Thread Series. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Figures1 Basic Profile for UN and UNR Screw Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Disposition of Diametral Tolerances, Allowance, and Crest Clearance for

Unified Inch Screw Thread Classes 1A, 2A, 1B, and 2B . . . . . . . . . . . . . . . . . . . . . 43 Disposition of Diametral Tolerances and Crest Clearances for Unified Inch

Screw Thread Classes 3A and 3B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Ratio of Pitch Diameter Change to Thickness of Coating on 60-deg

Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655 Effect of Electrodeposited Coatings on 60-deg External Threads . . . . . . . . . . . . . . . 666 Application of General Thread Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Tables1 Standard Series Threads (UN/UNR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Limits of Size for Standard Series Threads (UN/UNR) . . . . . . . . . . . . . . . . . . . . . . . . 83 Allowable Variations in Lead and Equivalent Change in Functional

Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384 Increments in Pitch Diameter Tolerance — Class 2A . . . . . . . . . . . . . . . . . . . . . . . . . . 565 Thread Form Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596 Basic Dimensions for Coarse-Thread Series (UNC/UNRC) . . . . . . . . . . . . . . . . . . . . 727 Basic Dimensions for Fine-Thread Series (UNF/UNRF) . . . . . . . . . . . . . . . . . . . . . . . 738 Basic Dimensions for Extra-Fine-Thread Series (UNEF/UNREF) . . . . . . . . . . . . . . . 749 Basic Dimensions for 4-Thread Series (4-UN/4-UNR) . . . . . . . . . . . . . . . . . . . . . . . . . 75

iv

10 Basic Dimensions for 6-Thread Series (6-UN/6-UNR) . . . . . . . . . . . . . . . . . . . . . . . . . 7611 Basic Dimensions for 8-Thread Series (8-UN/8-UNR) . . . . . . . . . . . . . . . . . . . . . . . . . 7712 Basic Dimensions for 12-Thread Series (12-UN/12-UNR) . . . . . . . . . . . . . . . . . . . . . . 7913 Basic Dimensions for 16-Thread Series (16-UN/16-UNR) . . . . . . . . . . . . . . . . . . . . . . 8114 Basic Dimensions for 20-Thread Series (20-UN/20-UNR) . . . . . . . . . . . . . . . . . . . . . . 8315 Basic Dimensions for 28-Thread Series (28-UN/28-UNR) . . . . . . . . . . . . . . . . . . . . . . 8416 Basic Dimensions for 32-Thread Series (32-UN/32-UNR) . . . . . . . . . . . . . . . . . . . . . . 8517A Outline Guide for Determining Limits of Size of External Threads . . . . . . . . . . . . 8617B Outline Guide for Determining Limits of Size of Internal Threads . . . . . . . . . . . . . 8618A Examples of External Screw Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8718B Examples of Internal Screw Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9019 Allowable Variation in 30 deg Basic Half Angle of External and Internal

Screw Threads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9220 General Symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Nonmandatory AppendicesA Terminology and Identification of Unified Inch Screw Threads . . . . . . . . . . . . . . . . 95B Thread Strength Design Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97C Unified Inch Screw Threads — Metric Translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98D Special Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134E Changes to ASME B1.1-1989 Tables 3A and 3B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

v



FOREWORD

This Standard is the outgrowth of and supersedes previous editions that were published asB1-1924, B1.1-1935, B1.1-1949, B1.1-1960, B1.1-1974, B1.1-1982, and B1.1-1989. Throughout suchdevelopment, special attention has been given to the practical aspects of thread standardization,and many details of the current Standard result from studies and tests based on user problems.For example, there was disclosed the need for free assembly in high-production industries andthe desirability of making some provision for threads that require a coating. The tolerance classes2A/2B were developed to meet these two major requirements as well as to provide a generalstandard for externally and internally threaded fasteners. Thread symbols and nomenclaturewere changed to be expressed according to ASME B1.7. Thread acceptability now refers toASME B1.3.

This issue includes the following changes to ASME B1.1-1989:(a) The revision of some of the values in Table 2. These revisions are the result of the application

of the consistent eight place decimal and rounding rules established in ASME B1.30-1992 thatwere mandated for use in all new and future revisions of ASME B1 documents. ASME B1.30 wasdeveloped under the direction of the B1 Committee as the basis for rounding of decimal valuesassociated with the computation of screw thread dimensions. Using the thread calculation formu-las in paras. 5 and 8 of this document and following the rounding rules of B1.30 all parties usinga calculator or standard computer spreadsheet program will derive precisely the same values.

Table E-1 of Nonmandatory Appendix E identifies the thread sizes in Table 2 that have beenrevised and lists the dimensions from the ASME B1.1-1989 standard. The majority of the dimen-sional changes are within ± 0.0001 in.

Paragraph 8.2.1 states that both the values in Tables 2 and E-1 should be considered acceptableuntil a future revision of this standard makes the values in Table 2 the only acceptable values.

(b) Former Table 3B has been moved to Nonmandatory Appendix D. This table providescalculated values for various UNS (Unified Specials). ASME B1 strongly urges the adoption ofthe standard thread sizes in Table 2 whenever possible instead of those listed in Table D-1.

(c) Former Tables 20 through 30 have been eliminated because the allowances and tolerancescontained in them was determined to be redundant with data provided in Table 2.

(d) Former Tables 31 through 40 have been moved to Nonmandatory Appendix D and wererenamed Tables D-2 through D-11. These tables were used in the past for the quick calculationof special threads. In some cases the derived values resulted in values that differ from thosederived by use of the formulas in paras. 5 and 8 of ASME B1.1. All future special threads shouldbe based on calculations in paras. 5 and 8 in this document using the rounding rules in ASMEB1.30 to ensure uniformity and consistency.

(e) All references to percent of thread engagement have been eliminated from this document.Past changes in the thread form designation of the “basic” thread height from 0.750H to 0.625Hconfused the calculation of percent of thread engagement. This calculation has been used in thepast for threaded products users to determine drill size selection. It is now recommended thatusers select a drill size that will result in a hole size that lies between the maximum and minimumsize of the internal thread’s minor diameter shown in the tables included in this Standard.

(f) The definition of “functional diameter” has been included in this document and the termhas been added in Table 2 in the same column as “pitch diameter” since both characteristics havethe same limits of size.

(g) The effects of coating on threads have been explained in more depth in para. 7.The Unified Screw Threads Standard is an integrated system of threads for fastening purposes

in mechanisms and structures. Its outstanding characteristic is general interchangeability ofthreads, achieved through the standardization of thread form, diameter-pitch combinations, andlimits of size.

The Standard has as its original basis the work done more than a century ago by WilliamSellers in the United States and Sir Joseph Whitworth in Great Britain. Throughout the intervening

vi

years there have been many further developments and revisions, culminating in the system ofUnified Threads approved and adopted for use by all inch-using countries.

The achievements represented by ASME B1.1 in development, standardization, and unificationare the result of cooperation and coordination of many organizations, including The AmericanSociety of Mechanical Engineers, Society of Automotive Engineers, National Institute of Scienceand Technology (formerly National Bureau of Standards), Committee B1, the former NationalScrew Thread Commission, the former Interdepartmental Screw Thread Committee, British Stan-dards Institution, Canadian Standards Association, and American National Standards Institute.

Unification of screw thread standards received its impetus from the need for interchangeabilityamong the billions of fasteners used in the complex equipment of modern technology and madein different countries. Equally important, however, are international trade in mechanisms of allkinds and the servicing of transportation equipment which moves from country to country. Thesehave made unification not only highly advantageous, but practically essential. In sizes 1⁄4 in. andlarger, complete unification of certain thread series and six tolerance classes was signaled by thesigning of an accord on November 18, 1948. Since that time, further unification has been extendedinto smaller sizes. Working through Technical Committee No. 1 of the International Organizationfor Standardization (ISO), the unified standard was adopted as an ISO inch screw thread standard,ISO 5864, parallel to the ISO metric screw thread system. Both systems have a common basicprofile. The standard was subject to Quadripartite Standardization Agreement (QSTAG) 247, inthe ABCA Army Standardization Program of America, Britain, Canada, and Australia.

Suggestions for improvement of this Standard will be welcomed. They should be sent to theAmerican Society of Mechanical Engineers at ASME International, Three Park Avenue, New York,NY 10016-5990, U.S.A.

ASME B1.1-2003 was approved by the American National Standards Institute (ANSI) on March27, 2003.

vii



ASME STANDARDS COMMITTEE B1Standardization and Unification of Screw Threads

(The following is the roster of the Committee at the time of approval of this Standard.)

OFFICERS

A. L. Barrows, ChairD. S. George, Vice Chair

R. L. Crane, Secretary

COMMITTEE PERSONNEL

G. L. Allen, L. S. Starret Co.A. L. Barrows, Kennametal — IPGM. H. Bernier, Standard Nut and BoltF. G. Calderone, Quality Systems ImplementersR. L. Crane, The American Society of Mechanical EngineersL. N. Dixon, Jr., General ElectricR. Dodge, Pennoyer-Dodge Co.G. A. Flannery, Mercury Gage Co.D. Skierski, Alternate, Mercury Gage Co.H. N. Frost, Defense Supply Center PhildelphiaJ. O. Gehret, Vermont Thread GageD. S. George, Ford Motor Co.J. R. Gervasi, Kerr Lakeside Inc.J. Greenslade, Greenslade & Co.J. Vance, Alternate, Greenslade and Co.R. J. Hukari, SPS TehnologiesL. C. Johnson, The Johnson Gage Co.D. D. Katz, Precision Fittings

SUBCOMMITTEE 1 — UNIFIED SCREW THREADS

A. L. Barrows, Chair, Kennametal — IPGD. Miskinis, Vice-Chair, Kennametal — IPGM. H. Bernier, Standard Nut and BoltM. Cox, Frank J. Cox Sales, Ltd.L. N. Dixon, Jr., General ElectricH. N. Frost, Defense Supply Center PhiladelphiaD. S. George, Ford Motor Co.J. R. Gervasi, Kerr Lakeside, Inc.J. Greenslade, Greenslade & Co.J. Vance, Alternate, Greenslade & Co.D. H. Honsinger, ConsultantR. J. Hukari, SPS TehnologiesL. C. Johnson, The Johnson Gage Co.J. M. Kane, Boeing

viii

R. P. Knittel, Leitech–U.S., Ltd.B. Larzelere, Deltronic Corp.L. L. Lord, Caterpillar, Inc.R. L. Tennis, Alternate, Caterpillar, Inc.M. H. McWilliams, PMC Gage, Inc.D. Miskinis, Kennametal–IPGW. R. Newman, ConsultantM. W. Rose, Southern Gage, Inc.W. A. Watts, Alternate, Southern Gage, Inc.E. Schwartz, ConsultantR. H. Searr, ConsultantB. F. Sheffler, Dresser-Rand Co.A. D. Shepherd, Jr., Emuge Corp.A. G. Strang, ConsultantR. D. Strong, General Motors Corp.A. F. Thibodeau, Swanson Tool Manufacturing Co.R. E. Vincent, Jr., General Plug Manufacturing Co.C. J. Wilson, Industrial Fasteners InstituteF. W. Akstens, Alternate, Industrial Fasteners Institute

D. D. Katz, Precision FittingsR. P. Knittel, Leitech — U.S., Ltd.B. Larzelere, Deltronic Corp.L. L. Lord, ConsultantW. R. Newman, ConsultantE. Schwartz, ConsultantR. H. Searr, ConsultantB. F. Sheffler, Dresser-Rand Co.J. D. Smith, Hi-Shear Corp.R. D. Strong, GM Vehicle Engineering Ctr.A. F. Thibodeau, Swanson Tool Manufacturing, Inc.R. E. Vincent, Jr., General Plug Manufacturing Co.C. J. Wilson, Industrial Fasteners InstituteF. W. Akstens, Alternate, Industrial Fasteners Institute

ASME B1.1-2003

UNIFIED INCH SCREW THREADS

(UN AND UNR THREAD FORM)

1 GENERAL

1.1 Scope

This Standard specifies the thread form, series, class,allowance, tolerance, and designation for unified screwthreads. (In order to emphasize that unified screwthreads are based on inch modules, they may be denotedunified inch screw threads.) Several variations in threadform have been developed for unified threads; however,this Standard covers only UN and UNR thread forms.

For easy reference, a metric translation of this Stan-dard has been incorporated as Nonmandatory Appen-dix 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 threads.Unified 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 subse-quently 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 designa-tion, 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 interchange-able. 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

1

ISO metric screw threads are not mechanically inter-changeable.

1.5 Designations

Unified thread sizes (specific combinations of diame-ter 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 letter“A” 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 Institute,Inc., 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 Threads

ASME 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 BlanksASME B94.11, Twist DrillsASME 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 Profile

Publisher: International Organization for Standardiza-tion (ISO), 1 rue de Varembé, Case Postale 56, CH-1211, Genève 20, Switzerland/Suisse



ASME B1.1-2003 UNIFIED INCH SCREW THREADS

1.7 Acceptability

Acceptability of product threads shall be in accor-dance with ASME B1.3. Gages and gaging shall be inaccordance with ASME B1.2.

1.8 Reference Temperature

The reference temperature is 68°F for dimensionsdefined by this system.

1.9 Units of Measure

All dimensions in this Standard, including all tables,are in inches unless otherwise specified.

1.10 Federal Government Use

When this Standard is approved by the Departmentof Defense and federal agencies and is incorporated intoFED-STD-H28/2, Screw-Thread Standards for FederalServices, para. 2, the use of this Standard by the federalgovernment will be subject to all the requirements andlimitations of FED-STD-H28/2.

2 SCREW THREAD PROFILE

2.1 Scope

The basic profile and design profiles are defined inthis paragraph and are the basis of all thread dimensionsgiven in this Standard.

2.2 Basic Profile

The basic profile for UN screw threads is identical tothat for UNR screw threads and is shown in Fig. 1.Profile applies to an axial plane.

For reference, the basic profile for UN and UNR screwthreads is identical to that for ISO metric screw threadsshown in ISO 68.

2.3 Design Profiles

The design profiles define the maximum-material con-ditions for external and internal threads with no allow-ance and are derived from the basic profile. The designprofiles of both external and internal screw threads varyfrom the basic profile.

2.3.1 Design Profiles of External Threads. The designprofiles of external UN and UNR screw threads areincluded in Figs. 2 and 3. A flat root contour is specifiedfor UN threads; however, it is permissible to providefor some threading tool crest wear. Therefore, a roundedroot contour cleared beyond the 0.250P flat width of thebasic profile is optional. The rounded root also reducesthe rate of threading tool crest wear and improvesfatigue strength over that of a flat root thread.

(a) The root contour of external UNR screw threadsshown in Figs. 2 and 3 shall have a smooth, continuous,nonreversing contour with a radius of curvature not lessthan 0.10825318P at any point and shall blend tangen-tially into the flanks and any straight segment. At the

2

maximum-material condition, the point of tangencyshall be at a distance not less than 0.54126588P (0.625H)below the basic major diameter.

NOTE: The maximum full root radius is 0.14433757P, but this maybe exceeded when the root contour consists of a combination offlats and radii.

(b) The design profiles of external UN and UNR screwthreads have flat crests. However, in practice, productthread crests may be flat, or partially corner rounded.A rounded crest tangent at a 0.125P flat is shown as anoption in Figs. 2 and 3.

2.3.2 Design Profile of Internal Threads. The designprofile of the internal UN screw thread is included inFigs. 2 and 3 (there is no internal UNR screw thread).In practice, it is necessary to provide for some threadingtool crest wear; therefore, the root of the design profileis rounded and cleared beyond the 0.125P flat width ofthe basic profile.

2.4 Formulas and Symbols

The formulas and symbols pertaining to the basicprofile and the design profiles are given in para. 10.

3 SCREW THREAD SERIES

3.1 Thread Series Definition

Thread series are groups of diameter-pitch combina-tions distinguished from each other by the number ofthreads per inch applied to a series of specific diameters.There are two general series classifications: standardand special.

3.1.1 Standard Series. The standard series consistsof three series with graded pitches (coarse, fine, andextra fine) and eight series with constant pitches (4, 6,8, 12, 16, 20, 28, and 32 threads per inch). The standardseries is shown in Table 1. Limits of size are shown inTable 2. See para. 8 for limits of size.

3.1.2 Special Series. The special series consists of allthreads with diameter-pitch combinations that are notincluded in the standard series. When allowances andtolerances of special series threads are derived from uni-fied formulation as shown in para. 5, the threads aredesignated UNS or UNRS. If allowance and toleranceare not derived from unified formulation, the threadsare designated “SPL 60 degree Form.” See para. 6 fordetails of designation.

3.2 Order of Selection

Wherever possible, selection should be made fromTable 2, Standard Series — Unified Screw Threads, pref-erence being given to the coarse- and fine-thread series.Second choice; if the threads in the standard series inTable 2 do not meet the requirements of the design,

UNIFIED INCH SCREW THREADS ASME B1.1-2003

0.86602540P(H)

P

60 deg

30 deg

90 deg

Axis of screw thread

D bsc, d bsc

D2 bsc, d2 bsc

D1 bsc, d1 bsc

0.125P0.10825318P

(0.125H)

0.32475953P(0.375H)

0.54126588P(0.625H)

0.21650635P(0.25H)

0.250P

0.500P

0.500P

GENERAL NOTE: For standardization, values have been established based on a function of pitch, P. The thread valuesbased on a function of height, H, are used for reference only.

Fig. 1 Basic Profile for UN and UNR Screw Threads

special thread sizes should be selected from Table E-1 ofNonmandatory Appendix E and their limits calculatedusing the formulas in para. 8. The limits in Table D-1 ofNonmandatory Appendix D are for reference only andare not recommended for new applications.

3.3 Coarse-Thread Series Applications

The coarse-thread series (UNC/UNRC) is generallyused for the bulk production of screws, bolts, and nuts.It is commonly used in relatively low-strength materialssuch as cast iron, aluminum, magnesium, brass, bronze,and plastic, because the coarse-thread series providemore resistance to internal thread stripping than the fineor extra-fine series. Coarse-thread series are advanta-geous where rapid assembly or disassembly is required,or if corrosion or damage from nicks due to handlingor use is likely.

3.4 Fine-Thread Series Applications

The fine-thread series (UNF/UNRF) is commonlyused for bolts and nuts in high-strength applications.This series has less thread depth and a larger minor

3

diameter than coarse-thread series. Consequently, thin-ner walls are permitted for internal threads and morestrength is available to external threads than for coarse-thread series of the same nominal size. In order to pre-vent internal thread stripping, a longer length of engage-ment is required for fine-thread series than for coarse-thread series for thread materials of the same strengthlevels. However, for both fine- and coarse-thread series,length of engagement in tapped holes must be selectedto meet strength requirements. This also allows for fineradjustment in cases such as a slotted nut and cotter pinassembly.

3.5 Extra-Fine-Thread Series ApplicationsThe extra-fine-thread series (UNEF/UNREF) is used

particularly for equipment and threaded parts thatrequire fine adjustment, such as bearing retaining nuts,adjusting screws, etc., and for thin-wall tubing andthin nuts.

3.6 Constant-Pitch Thread Series ApplicationsThe various constant-pitch series (UN/UNR) with 4,

6, 8, 12, 16, 20, 28, and 32 threads per inch, given in




UNR contour, see para. 2.3.1(a)

Min

imu

m m

ino

r d

iam

eter

of

exte

rnal

Min

imu

m m

ino

r d

iam

eter

of

inte

rnal

Max

imu

m m

ino

r d

iam

eter

of

inte

rnal

1/2 allowance (external only)

Basic form

0.041667P

0.125P UN (maximum) minor diameter of external

For UNR threads, this root is defined as a continuous rounded contour with a radius not less than 0.10825318P. For UN threads this root may be flat. See para. 2.3.1.

1/2 PD tolerance on internal

1/2 PD tolerance on external

1/2 allowance (external)

Max

imu

m m

ajo

r d

iam

eter

of

inte

rnal

Min

imu

m m

ajo

r d

iam

eter

of

inte

rnal

Max

imu

m m

ajo

r d

iam

eter

of

exte

rnal

Min

imu

m m

ajo

r d

iam

eter

of

exte

rnal

Bas

ic m

ajo

r d

iam

eter

Max

imu

m p

itch

dia

met

er o

f in

tern

al

Min

imu

m p

itch

dia

met

er o

f in

tern

al

Bas

ic p

itch

dia

met

er

Max

imu

m p

itch

dia

met

er o

f ex

tern

al

Min

imu

m p

itch

dia

met

er o

f ex

tern

al

1 /2

tole

ran

ce o

n m

ino

r d

iam

eter

of

inte

rnal

1/2 tolerance on major diameter of internal

In practice, crests may be partially or fully rounded. See para. 2.3.1(b).

Internal Thread

External Thread

UN

R m

axim

um

min

or

dia

met

er o

f ex

tern

al

30 deg

60 deg

0.125P

0.250P

GENERAL NOTE: Lead and angle tolerances are defined in para. 9.

Fig. 2 Disposition of Diametral Tolerances, Allowance, and Crest Clearance for Unified Inch Screw ThreadClasses 1A, 2A, 1B, and 2B

4


UNR contour, see para. 2.3.1(a)

UN (maximum) minor diameter or external

Min

imu

m m

ino

r d

iam

eter

of

exte

rnal

Min

imu

m m

ino

r d

iam

eter

of

inte

rnal

Max

imu

m m

ino

r d

iam

eter

of

inte

rnal

Basic form

0.041667P

0.125P

For UNR threads, this root is defined as a continuous rounded contour with a radius not less than 0.10825318P. For UN threads this root may be flat. See para. 2.3.1.

1/2 PD tolerance on internal1/2 allowance on (external)

Max

imu

m m

ajo

r d

iam

eter

of

inte

rnal

Min

imu

m m

ajo

r d

iam

eter

of

inte

rnal

Max

imu

m m

ajo

r d

iam

eter

of

exte

rnal

Min

imu

m m

ajo

r d

iam

eter

of

exte

rnal

Bas

ic m

ajo

r d

iam

eter

of

exte

rnal

an

d in

tern

al

Max

imu

m p

itch

dia

met

er o

f in

tern

al

Min

imu

m p

itch

dia

met

er o

f in

tern

al

Bas

ic m

ajo

r d

iam

eter

of

exte

rnal

an

d in

tern

al

Max

imu

m p

itch

dia

met

er o

f ex

tern

al

Min

imu

m p

itch

dia

met

er o

f ex

tern

al

1 /2

tole

ran

ce o

n m

ino

r d

iam

eter

of

inte

rnal

1/2 tolerance on major diameter of internal

In practice, crests may be partially or fully rounded. See para. 2.3.1(b).

Internal Thread

External Thread

UN

R m

axim

um

min

or

dia

met

er o

f ex

tern

al

60 deg

0.125P

0.250P

30 deg

GENERAL NOTE: Lead and angle tolerances are defined in para. 9.

Fig. 3 Disposition of Diametral Tolerances and Crest Clearances for Unified Inch Screw ThreadClasses 3A and 3B

5




Table 1 Standard Series Threads (UN/UNR)

Threads/in.

Series With GradedPitches

Basic ExtraNominal Size, in. Series With Constant PitchesMajor Course Fine Fine Nominal

Primary Secondary Diameter UNC UNF UNEF 4-UN 6-UN 8-UN 12-UN 16-UN 20-UN 28-UN 32-UN Size, in.

0 . . . 0.0600 . . . 80 . . . . . . . . . . . . . . . . . . . . . . . . . . . 0. . . 1 0.0730 64 72 . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 . . . 0.0860 56 64 . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. . . 3 0.0990 48 56 . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4 . . . 0.1120 40 48 . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 . . . 0.1250 40 44 . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 . . . 0.1380 32 40 . . . . . . . . . . . . . . . . . . . . . . . . UNC 68 . . . 0.1640 32 36 . . . . . . . . . . . . . . . . . . . . . . . . UNC 810 . . . 0.1900 24 32 . . . . . . . . . . . . . . . . . . . . . . . . UNF 10

. . . 12 0.2160 24 28 32 . . . . . . . . . . . . . . . . . . UNF UNEF 12

1⁄4 . . . 0.2500 20 28 32 . . . . . . . . . . . . . . . UNC UNF UNEF1⁄4

5⁄16 . . . 0.3125 18 24 32 . . . . . . . . . . . . . . . 20 28 UNEF5⁄16

3⁄8 . . . 0.3750 16 24 32 . . . . . . . . . . . . UNC 20 28 UNEF3⁄8

7⁄16 . . . 0.4375 14 20 28 . . . . . . . . . . . . 16 UNF UNEF 327⁄16

1⁄2 . . . 0.5000 13 20 28 . . . . . . . . . . . . 16 UNF UNEF 321⁄2

9⁄16 . . . 0.5625 12 I8 24 . . . . . . . . . UNC 16 20 28 329⁄16

5⁄8 . . . 0.6250 11 18 24 . . . . . . . . . 12 16 20 28 325⁄8

. . . 11⁄16 0.6875 . . . . . . 24 . . . . . . . . . 12 16 20 28 3211⁄16

3⁄4 . . . 0.7500 10 16 20 . . . . . . . . . 12 UNF UNEF 28 323⁄4

. . . 13⁄16 0.8125 . . . . . . 20 . . . . . . . . . 12 16 UNEF 28 3213⁄16

7⁄8 . . . 0.8750 9 14 20 . . . . . . . . . 12 16 UNEF 28 327⁄8

. . . 15⁄16 0.9375 . . . . . . 20 . . . . . . . . . 12 16 UNEF 28 3215⁄16

1 . . . 1.0000 8 12 20 . . . . . . UNC UNF 16 UNEF 28 32 1. . . 11⁄16 1.0625 . . . . . . 18 . . . . . . 8 12 16 20 28 . . . 1

1⁄1611⁄8 . . . 1.1250 7 12 18 . . . . . . 8 UNF 16 20 28 . . . 1

1⁄8. . . 13⁄16 1.1875 . . . . . . 18 . . . . . . 8 12 16 20 28 . . . 1

3⁄1611⁄4 . . . 1.2500 7 12 18 . . . . . . 8 UNF 16 20 28 . . . 1

1⁄4. . . 15⁄16 1.3125 . . . . . . 18 . . . . . . 8 12 16 20 28 . . . 1

5⁄1613⁄8 . . . 1.3750 6 12 18 . . . UNC 8 UNF 16 20 28 . . . 1

3⁄8. . . 17⁄16 1.4375 . . . . . . 18 . . . 6 8 12 16 20 28 . . . 1

7⁄1611⁄2 . . . 1.5000 6 12 18 . . . UNC 8 UNF 16 20 28 . .. 1

1⁄2. . . 19⁄16 1.5625 . . . . . . 18 . . . 6 8 12 16 20 . . . . . . 1

9⁄1615⁄8 . . . 1.6250 . . . . . . 18 . . . 6 8 12 16 20 . . . . . . 1

5⁄8. . . 111⁄16 1.6875 . . . . . . 18 . . . 6 8 12 16 20 . . . . . . 1

11⁄1613⁄4 . . . 1.7500 5 . . . . . . . . . 6 8 12 16 20 . . . . . . 1

3⁄4. . . 113⁄16 1.8125 . . . . . . . . . . . . 6 8 12 16 20 . . . . . . 1

13⁄1617⁄8 . . . 1.8750 . . . . . . . . . . . . 6 8 12 16 20 . . . . . . 1

7⁄8. . . 115⁄16 1.9375 . . . . . . . . . . . . 6 8 12 16 20 . . . . . . 1

15⁄16

2 . . . 2.0000 41⁄2 . . . . . . . . . 6 8 12 16 20 . . . . . . 2. . . 21⁄8 2.1250 . . . . . . . . . . . . 6 8 12 16 20 . . . . . . 2

1⁄821⁄4 . . . 2.2500 4

1⁄2 . . . . . . . . . 6 8 12 16 20 . . . . . . 21⁄4

. . . 23⁄8 2.3750 . . . . . . . . . . . . 6 8 12 16 20 . . . . . . 23⁄8

21⁄2 . . . 2.5000 4 . . . . . . UNC 6 8 12 16 20 . . . . . . 21⁄2

. . . 25⁄8 2.6250 . . . . . . . . . 4 6 8 12 16 20 . . . . . . 25⁄8

23⁄4 . . . 2.7500 4 . . . . . . UNC 6 8 12 16 20 . . . . . . 23⁄4

. . . 27⁄8 2.8750 . . . . . . . . . 4 6 8 12 16 20 . . . . . . 27⁄8

6


Table 1 Standard Series Threads (UN/UNR) (Cont’d)

Threads/in.

Series With GradedPitches

Basic ExtraNominal Size, in. Series With Constant PitchesMajor Course Fine Fine Nominal

Primary Secondary Diameter UNC UNF UNEF 4-UN 6-UN 8-UN 12-UN 16-UN 20-UN 28-UN 32-UN Size, in.

3 . . . 3.0000 4 . . . . . . UNC 6 8 12 16 20 . . . . . . 3. . . 31⁄8 3.1250 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 3

1⁄831⁄4 . . . 3.2500 4 . . . . . . UNC 6 8 12 16 . . . . . . . . . 3

1⁄4. . . 33⁄8 3.3750 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 3

3⁄831⁄2 . . . 3.5000 4 . . . . . . UNC 6 8 12 16 . . . . . . . . . 3

1⁄2. . . 35⁄8 3.6250 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 3

5⁄833⁄4 . . . 3.7500 4 . . . . . . UNC 6 8 12 16 . . . . . . . . . 3

3⁄4. . . 37⁄8 3.8750 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 3

7⁄8

4 . . . 4.0000 4 . . . . . . UNC 6 8 12 1.6 . . . . . . . . . 4. . . 41⁄8 4.1250 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 4

1⁄841⁄4 . . . 4.2500 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 4

1⁄4. . . 43⁄8 4.3750 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 4

3⁄841⁄2 . . . 4.5000 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 4

1⁄2. . . 45⁄8 4.6250 . . . . . . . . . 4 6 8 12 16 .. . . . . . . 4

5⁄843⁄4 . . . 4.7500 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 4

3⁄4. . . 47⁄8 4.8750 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 4

7⁄8

5 . . . 5.0000 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5. . . 51⁄8 5.1250 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5

1⁄851⁄4 . . . 5.2500 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5

1⁄4. . . 53⁄8 5.3750 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5

3⁄851⁄2 . . . 5.5000 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5

1⁄2. . . 55⁄8 5.6250 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5

5⁄853⁄4 . . . 5.7500 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5

3⁄4. . . 57⁄8 5.8750 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 5

7⁄86 . . . 6.0000 . . . . . . . . . 4 6 8 12 16 . . . . . . . . . 6

GENERAL NOTE: Series designation shown indicates the UN thread form; however, the UNR thread form may be specifiedby substituting UNR in place of UN in all designations for external use only.

Table 1, offer a comprehensive range of diameter-pitchcombinations for those purposes where the threads inthe coarse-, fine-, and extra-fine-thread series do notmeet the particular requirements of the design. The pri-mary sizes of the 8-UN, 12-UN, and 16-UN series shownin Table 1 are the most commonly used.

Whenever a thread in a constant-pitch series alsoappears in the UNC, UNF, or UNEF series, the symbolsand tolerances for limits of size of those standard seriesare applicable.

3.6.1 8-Thread Series. The 8-thread series (8-UN) isa uniform-pitch series for large diameters or as a com-promise between coarse and fine thread series. Althoughoriginally intended for high-pressure-joint bolts andnuts, it is now widely used as a substitute for the coarsethread series for diameters larger than 1 in.

3.6.2 12-Thread Series. The 12-thread series (12-UN)is a uniform-pitch series for large diameters requiring

7

threads of medium-fine pitch. Although originallyintended for boiler practice, it is now used as a continua-tion of the fine thread series for diameters larger than11⁄2 in.

3.6.3 16-Thread Series. The 16-thread series (16-UN)is a uniform-pitch series for large diameters requiringfine-pitch threads. It is suitable for adjusting collars andretaining nuts and also serves as a continuation of theextra-fine thread series for diameters larger than 111⁄16 in.

3.7 Fine Threads for Thin-Wall Tubing

The limits of size for a 28-thread series, ranging from0.216 in. to 1.5 in. nominal size, are included in Table 2.These threads are recommended for general use on thin-wall tubing. The 27-thread series is no longer standardbut is included in Table D-1 of Nonmandatory Appen-dix D.




Tabl

e2

Lim

its

ofSi

zefo

rSt

anda

rdSe

ries

Thre

ads

(UN

/UN

R)

Exte

rnal

[Not

e(1

)]In

tern

al[N

ote

(1)]

Pitc

hD

iam

eter

and

UN

RM

inor

Func

tion

alD

iam

eter

Pitc

hD

iam

eter

and

Dia

met

er,

Maj

orD

iam

eter

[Not

e(4

)]Fu

ncti

onal

Dia

met

erS

erie

sM

ax.

Maj

orM

inor

Dia

met

er[N

ote

(4)]

Nom

inal

Siz

ean

dD

esig

-M

ax.

Min

.M

ax.

Tole

ranc

e[N

ote

(6)]

Dia

met

er,

Thre

ads/

in.

nati

onCl

ass

Allo

wan

ce[N

ote

(2)]

Min

.[N

ote

(3)]

[Not

e(2

)]M

in.

[Not

e(5

)](R

ef.)

Clas

sM

in.

Max

.M

in.

Max

.To

lera

nce

Min

.

0–80

or0.

060–

80U

NF

2A0.

0005

0.05

950.

0563

...

0.05

140.

0496

0.00

1762

0.04

462B

0.04

650.

0514

0.05

190.

0542

0.00

230.

0600

3A0.

0000

0.06

000.

0568

...

0.05

190.

0506

0.00

1300

0.04

513B

0.04

650.

0514

0.05

190.

0536

0.00

170.

0600

(7)

1–64

or0.

073–

64U

NC

2A0.

0006

0.07

240.

0686

...

0.06

230.

0603

0.00

1970

0.05

382B

0.05

610.

0622

0.06

290.

0655

0.00

260.

0730

(7)

3A0.

0000

0.07

300.

0692

...

0.06

290.

0614

0.00

1500

0.05

443B

0.05

610.

0622

0.06

290.

0648

0.00

190.

0730

(7)

1–72

or0.

073–

72U

NF

2A0.

0006

0.07

240.

0689

...

0.06

340.

0615

0.00

1899

0.05

592B

0.05

80.

0634

0.06

400.

0665

0.00

250.

0730

(7)

3A0.

0000

0.07

300.

0695

...

0.06

400.

0626

0.00

1400

0.05

653B

0.05

800.

0634

0.06

400.

0659

0.00

190.

0730

2–56

or0.

086–

56U

NC

2A0.

0006

0.08

540.

0813

...

0.07

380.

0717

0.00

2127

0.06

412B

0.06

670.

0737

0.07

440.

0772

0.00

280.

0860

3A0.

0000

0.08

600.

0819

...

0.07

440.

0728

0.00

1600

0.06

473B

0.06

670.

0737

0.07

440.

0765

0.00

210.

0860

(7)

2–64

or0.

086–

64U

NF

2A0.

0006

0.08

540.

0816

...

0.07

530.

0733

0.00

2040

0.06

682B

0.06

910.

0752

0.07

590.

0786

0.00

270.

0860

(7)

3A0.

0000

0.08

600.

0822

...

0.07

590.

0744

0.00

1500

0.06

743B

0.06

910.

0752

0.07

590.

0779

0.00

200.

0860

3–48

or0.

099–

48U

NC

2A0.

0007

0.09

830.

0938

...

0.08

480.

0825

0.00

2302

0.07

352B

0.07

640.

0845

0.08

550.

0885

0.00

300.

0990

3A0.

0000

0.09

900.

0945

...

0.08

550.

0838

0.00

1700

0.07

423B

0.07

640.

0845

0.08

550.

0877

0.00

220.

0990

3–56

or0.

099–

56U

NF

2A0.

0007

0.09

830.

0942

...

0.08

670.

0845

0.00

2191

0.07

702B

0.07

970.

0865

0.08

740.

0902

0.00

280.

0990

3A0.

0000

0.09

900.

0949

...

0.08

740.

0858

0.00

1600

0.07

773B

0.07

970.

0865

0.08

740.

0895

0.00

210.

0990

4–40

or0.

112–

40U

NC

2A0.

0008

0.11

120.

1061

...

0.09

500.

0925

0.00

2507

0.08

142B

0.08

490.

0939

0.09

580.

0991

0.00

330.

1120

3A0.

0000

0.11

200.

1069

...

0.09

580.

0939

0.00

1900

0.08

223B

0.08

490.

0939

0.09

580.

0982

0.00

240.

1120

4–48

or0.

112–

48U

NF

2A0.

0007

0.11

130.

1068

...

0.09

780.

0954

0.00

2361

0.08

652B

0.08

940.

0968

0.09

850.

1016

0.00

310.

1120

3A0.

0000

0.11

200.

1075

...

0.09

850.

0967

0.00

1800

0.08

723B

0.08

940.

0968

0.09

850.

1008

0.00

230.

1120

5–40

or0.

125–

40U

NC

2A0.

0008

0.12

420.

1191

...

0.10

800.

1054

0.00

2562

0.09

442B

0.09

790.

1062

0.10

880.

1121

0.00

330.

1250

3A0.

0000

0.12

500.

1199

...

0.10

880.

1069

0.00

1900

0.09

523B

0.09

790.

1062

0.10

880.

1113

0.00

250.

1250

5–44

or0.

125–

44U

NF

2A0.

0007

0.12

430.

1195

...

0.10

950.

1070

0.00

2484

0.09

722B

0.10

040.

1079

0.11

020.

1134

0.00

320.

1250

3A0.

0000

0.12

500.

1202

...

0.11

020.

1083

0.00

1900

0.09

793B

0.10

040.

1079

0.11

020.

1126

0.00

240.

1250

6–32

or0.

138–

32U

NC

2A0.

0008

0.13

720.

1312

...

0.11

690.

1141

0.00

2820

0.10

002B

0.10

40.

114

0.11

770.

1214

0.00

370.

1380

(7)

3A0.

0000

0.13

800.

1320

...

0.11

770.

1156

0.00

2100

0.10

083B

0.10

400.

1139

0.11

770.

1204

0.00

270.

1380

6–40

or0.

138–

40U

NF

2A0.

0008

0.13

720.

1321

...

0.12

100.

1184

0.00

2614

0.10

742B

0.11

10.

119

0.12

180.

1252

0.00

340.

1380

3A0.

0000

0.13

800.

1329

...

0.12

180.

1198

0.00

2000

0.10

823B

0.11

100.

1186

0.12

180.

1243

0.00

250.

1380

8


Tabl

e2

Lim

its

ofSi

zefo

rSt

anda

rdSe

ries

Thre

ads

(UN

/UN

R)(C

ont’

d)

Exte

rnal

[Not

e(1

)]In

tern

al[N

ote

(1)]

Pitc

hD

iam

eter

and

UN

RM

inor

Func

tion

alD

iam

eter

Pitc

hD

iam

eter

and

Dia

met

er,

Maj

orD

iam

eter

[Not

e(4

)]M

inor

Func

tion

alD

iam

eter

Ser

ies

Max

.M

ajor

Dia

met

er[N

ote

(4)]

Nom

inal

Siz

ean

dD

esig

-M

ax.

Min

.M

ax.

Tole

ranc

e[N

ote

(6)]

Dia

met

er,

Thre

ads/

in.

nati

onCl

ass

Allo

wan

ce[N

ote

(2)]

Min

.[N

ote

(3)]

[Not

e(2

)]M

in.

[Not

e(5

)](R

ef.)

Clas

sM

in.

Max

.M

in.

Max

.To

lera

nce

Min

.

8–

32or

0.16

4–

32U

NC

2A0.

0009

0.16

310.

1571

...

0.14

280.

1399

0.00

2916

0.12

592B

0.13

00.

139

0.14

370.

1475

0.00

380.

1640

(7)

3A0.

0000

0.16

400.

1580

...

0.14

370.

1415

0.00

2200

0.12

683B

0.13

000.

1388

0.14

370.

1465

0.00

280.

1640

8–

36or

0.16

4–

36U

NF

2A0.

0008

0.16

320.

1577

...

0.14

520.

1424

0.00

2804

0.13

012B

0.13

40.

142

0.14

600.

1496

0.00

360.

1640

3A0.

0000

0.16

400.

1585

...

0.14

600.

1439

0.00

2100

0.13

093B

0.13

400.

1416

0.14

600.

1487

0.00

270.

1640

(7)

10–

24or

0.19

0–

24U

NC

2A0.

0010

0.18

900.

1818

...

0.16

190.

1586

0.00

3319

0.13

942B

0.14

50.

155

0.16

290.

1672

0.00

430.

1900

3A0.

0000

0.19

000.

1828

...

0.16

290.

1604

0.00

2500

0.14

043B

0.14

500.

1555

0.16

290.

1661

0.00

320.

1900

10–

32or

0.19

0–

32U

NF

2A0.

0009

0.18

910.

1831

...

0.16

880.

1658

0.00

3004

0.15

192B

0.15

60.

164

0.16

970.

1736

0.00

390.

1900

3A0.

0000

0.19

000.

1840

...

0.16

970.

1674

0.00

2300

0.15

283B

0.15

600.

1641

0.16

970.

1726

0.00

290.

1900

12–

24or

0.21

6–

24U

NC

2A0.

0010

0.21

500.

2078

...

0.18

790.

1845

0.00

3400

0.16

542B

0.17

10.

181

0.18

890.

1933

0.00

440.

2160

3A0.

0000

0.21

600.

2088

...

0.18

890.

1863

0.00

2600

0.16

643B

0.17

100.

1807

0.18

890.

1922

0.00

330.

2160

12–

28or

0.21

6–

28U

NF

2A0.

0010

0.21

500.

2085

...

0.19

180.

1886

0.00

3224

0.17

252B

0.17

70.

186

0.19

280.

1970

0.00

420.

2160

3A0.

0000

0.21

600.

2095

...

0.19

280.

1904

0.00

2400

0.17

353B

0.17

700.

1857

0.19

280.

1959

0.00

310.

2160

(7)

12–

32or

0.21

6–

32U

NEF

2A0.

0010

0.21

500.

2090

...

0.19

470.

1915

0.00

3184

0.17

782B

0.18

20.

190

0.19

570.

1998

0.00

410.

2160

3A0.

0000

0.21

600.

2100

...

0.19

570.

1933

0.00

2400

0.17

883B

0.18

200.

1895

0.19

570.

1988

0.00

310.

2160

1 ⁄4

–20

or0.

2500

–20

UN

C1A

0.00

110.

2489

0.23

67..

.0.

2164

0.21

080.

0056

000.

1894

1B0.

196

0.20

70.

2175

0.22

480.

0073

0.25

002A

0.00

110.

2489

0.24

080.

2367

0.21

640.

2127

0.00

3731

0.18

942B

0.19

60.

207

0.21

750.

2224

0.00

490.

2500

3A0.

0000

0.25

000.

2419

...

0.21

750.

2147

0.00

2800

0.19

053B

0.19

600.

2067

0.21

750.

2211

0.00

360.

2500

1 ⁄4

–28

or0.

2500

–28

UN

F1A

0.00

100.

2490

0.23

92..

.0.

2258

0.22

080.

0050

000.

2065

1B0.

211

0.22

0.22

680.

2333

0.00

650.

2500

2A0.

0010

0.24

900.

2425

...

0.22

580.

2225

0.00

3322

0.20

652B

0.21

10.

220

0.22

680.

2311

0.00

430.

2500

3A0.

0000

0.25

000.

2435

...

0.22

680.

2243

0.00

2500

0.20

753B

0.21

100.

2190

0.22

680.

2300

0.00

320.

2500

1 ⁄4

–32

or0.

2500

–32

UN

EF2A

0.00

100.

2490

0.24

30..

.0.

2287

0.22

550.

0032

290.

2118

2B0.

216

0.22

40.

2297

0.23

390.

0042

0.25

003A

0.00

000.

2500

0.24

40..

.0.

2297

0.22

730.

0024

000.

2128

3B0.

2160

0.22

290.

2297

0.23

280.

0031

0.25

00

5 ⁄16

–18

or0.

3125

–18

UN

C1A

0.00

120.

3113

0.29

82..

.0.

2752

0.26

910.

0061

000.

2451

1B0.

252

0.26

50.

2764

0.28

430.

0079

0.31

252A

0.00

120.

3113

0.30

260.

2982

0.27

520.

2712

0.00

4041

0.24

512B

0.25

20.

265

0.27

640.

2817

0.00

530.

3125

3A0.

0000

0.31

250.

3038

...

0.27

640.

2734

0.00

3000

0.24

633B

0.25

200.

2630

0.27

640.

2803

0.00

390.

3125

(7)

5 ⁄16

–20

or0.

3125

–20

UN

2A0.

0012

0.31

130.

3032

...

0.27

880.

2747

0.00

4060

0.25

182B

0.25

80.

270

0.28

000.

2853

0.00

530.

3125

(7)

3A0.

0000

0.31

250.

3044

...

0.28

000.

2770

0.00

3000

0.25

303B

0.25

800.

2680

0.28

000.

2840

0.00

400.

3125

9




Tabl

e2

Lim

its

ofSi

zefo

rSt

anda

rdSe

ries

Thre

ads

(UN

/UN

R)(C

ont’

d)

Exte

rnal

[Not

e(1

)]In

tern

al[N

ote

(1)]

Pitc

hD

iam

eter

and

UN

RM

inor

Func

tion

alD

iam

eter

Pitc

hD

iam

eter

and

Dia

met

er,

Maj

orD

iam

eter

[Not

e(4

)]M

inor

Func

tion

alD

iam

eter

Ser

ies

Max

.M

ajor

Dia

met

er[N

ote

(4)]

Nom

inal

Siz

ean

dD

esig

-M

ax.

Min

.M

ax.

Tole

ranc

e[N

ote

(6)]

Dia

met

er,

Thre

ads/

in.

nati

onCl

ass

Allo

wan

ce[N

ote

(2)]

Min

.[N

ote

(3)]

[Not

e(2

)]M

in.

[Not

e(5

)](R

ef.)

Clas

sM

in.

Max

.M

in.

Max

.To

lera

nce

Min

.

5 ⁄16

–24

or0.

3125

–24

UN

F1A

0.00

110.

3114

0.30

06..

.0.

2843

0.27

880.

0055

000.

2618

1B0.

267

0.27

70.

2854

0.29

250.

0071

0.31

252A

0.00

110.

3114

0.30

42..

.0.

2843

0.28

060.

0036

600.

2618

2B0.

267

0.27

70.

2854

0.29

020.

0048

0.31

253A

0.00

000.

3125

0.30

53..

.0.

2854

0.28

270.

0027

000.

2629

3B0.

2670

0.27

540.

2854

0.28

900.

0036

0.31

25

(7)

5 ⁄16

–28

or0.

3125

–28

UN

2A0.

0010

0.31

150.

3050

...

0.28

830.

2848

0.00

3495

0.26

902B

0.27

40.

282

0.28

930.

2938

0.00

450.

3125

(7)

3A0.

0000

0.31

250.

3060

...

0.28

930.

2867

0.00

2600

0.27

003B

0.27

400.

2807

0.28

930.

2927

0.00

340.

3125

(7)

5 ⁄16

–32

or0.

3125

–32

UN

EF2A

0.00

100.

3115

0.30

55..

.0.

2912

0.28

790.

0033

020.

2743

2B0.

279

0.28

60.

2922

0.29

650.

0043

0.31

25(7

)3A

0.00

000.

3125

0.30

65..

.0.

2922

0.28

970.

0025

000.

2753

3B0.

2790

0.28

460.

2922

0.29

540.

0032

0.31

25

3 ⁄8

–16

or0.

3750

–16

UN

C1A

0.00

130.

3737

0.35

95..

.0.

3331

0.32

660.

0065

000.

2993

1B0.

307

0.32

10.

3344

0.34

290.

0085

0.37

502A

0.00

130.

3737

0.36

430.

3595

0.33

310.

3287

0.00

4363

0.29

932B

0.30

70.

321

0.33

440.

3401

0.00

570.

3750

3A0.

0000

0.37

500.

3656

...

0.33

440.

3311

0.00

3300

0.30

063B

0.30

700.

3182

0.33

440.

3387

0.00

430.

3750

3 ⁄8

–20

or0.

3750

–20

UN

2A0.

0012

0.37

380.

3657

...

0.34

130.

3372

0.00

4124

0.31

432B

0.32

10.

332

0.34

250.

3479

0.00

540.

3750

3A0.

0000

0.37

500.

3669

...

0.34

250.

3394

0.00

3100

0.31

553B

0.32

100.

3297

0.34

250.

3465

0.00

400.

3750

3 ⁄8

–24

or0.

3750

–24

UN

F1A

0.00

110.

3739

0.36

31..

.0.

3468

0.34

110.

0057

000.

3243

1B0.

330.

340.

3479

0.35

530.

0074

0.37

502A

0.00

110.

3739

0.36

67..

.0.

3468

0.34

300.

0038

040.

3243

2B0.

330

0.34

00.

3479

0.35

280.

0049

0.37

503A

0.00

000.

3750

0.36

78..

.0.

3479

0.34

500.

0029

000.

3254

3B0.

3300

0.33

720.

3479

0.35

160.

0037

0.37

50

3 ⁄8

–28

or0.

3750

–28

UN

2A0.

0011

0.37

390.

3674

...

0.35

070.

3471

0.00

3559

0.33

142B

0.33

60.

345

0.35

180.

3564

0.00

460.

3750

3A0.

0000

0.37

500.

3685

...

0.35

180.

3491

0.00

2700

0.33

253B

0.33

600.

3426

0.35

180.

3553

0.00

350.

3750

3 ⁄8

–32

or0.

3750

–32

UN

EF2A

0.00

100.

3740

0.36

80..

.0.

3537

0.35

030.

0033

660.

3368

2B0.

341

0.34

90.

3547

0.35

910.

0044

0.37

503A

0.00

000.

3750

0.36

90..

.0.

3547

0.35

220.

0025

000.

3378

3B0.

3410

0.34

690.

3547

0.35

800.

0033

0.37

50

7 ⁄16

–14

or0.

4375

–14

UN

C1A

0.00

140.

4361

0.42

06..

.0.

3897

0.38

260.

0071

000.

3510

1B0.

360.

376

0.39

110.

4003

0.00

920.

4375

2A0.

0014

0.43

610.

4258

0.42

060.

3897

0.38

500.

0047

130.

3510

2B0.

360

0.37

60.

3911

0.39

720.

0061

0.43

753A

0.00

000.

4375

0.42

72..

.0.

3911

0.38

760.

0035

000.

3524

3B0.

3600

0.37

170.

3911

0.39

570.

0046

0.43

75

(7)

7 ⁄16

–16

or0.

4375

–16

UN

2A0.

0014

0.43

610.

4267

...

0.39

550.

3909

0.00

4626

0.36

172B

0.37

00.

384

0.39

690.

4029

0.00

600.

4375

(7)

3A0.

0000

0.43

750.

4281

...

0.39

690.

3934

0.00

3500

0.36

313B

0.37

000.

3800

0.39

690.

4014

0.00

450.

4375

(7)

7 ⁄16

–20

or0.

4375

–20

UN

F1A

0.00

130.

4362

0.42

40..

.0.

4037

0.39

740.

0063

000.

3767

1B0.

383

0.39

50.

4050

0.41

310.

0081

0.43

752A

0.00

130.

4362

0.42

81..

.0.

4037

0.39

950.

0041

670.

3767

2B0.

383

0.39

50.

4050

0.41

040.

0054

0.43

753A

0.00

000.

4375

0.42

94..

.0.

4050

0.40

190.

0031

000.

3780

3B0.

3830

0.39

160.

4050

0.40

910.

0041

0.43

75

10


Tabl

e2

Lim

its

ofSi

zefo

rSt

anda

rdSe

ries

Thre

ads

(UN

/UN

R)(C

ont’

d)

Exte

rnal

[Not

e(1

)]In

tern

al[N

ote

(1)]

UN

RM

inor

Pitc

hD

iam

eter

and

Pitc

hD

iam

eter

and

Dia

met

er,

Maj

orD

iam

eter

Func

tion

alD

iam

eter

[Not

e(4

)]M

inor

Func

tion

alD

iam

eter

Ser

ies

Max

.M

ajor

Dia

met

er[N

ote

(4)]

Nom

inal

Siz

ean

dD

esig

-M

ax.

Min

.M

ax.

Tole

ranc

e[N

ote

(6)]

Dia

met

er,

Thre

ads/

in.

nati

onCl

ass

Allo

wan

ce[N

ote

(2)]

Min

.[N

ote

(3)]

[Not

e(2

)]M

in.

[Not

e(5

)](R

ef.)

Clas

sM

in.

Max

.M

in.

Max

.To

lera

nce

Min

.

(7)

7 ⁄16

–28

or0.

4375

–28

UN

EF2A

0.00

110.

4364

0.42

99..

.0.

4132

0.40

960.

0036

160.

3939

2B0.

399

0.40

70.

4143

0.41

900.

0047

0.43

753A

0.00

000.

4375

0.43

10..

.0.

4143

0.41

160.

0027

000.

3950

3B0.

3990

0.40

510.

4143

0.41

780.

0035

0.43

75

(7)

7 ⁄16

–32

or0.

4375

–32

UN

2A0.

0010

0.43

650.

4305

...

0.41

620.

4128

0.00

3423

0.39

932B

0.40

40.

411

0.41

720.

4216

0.00

440.

4375

3A0.

0000

0.43

750.

4315

...

0.41

720.

4146

0.00

2600

0.40

033B

0.40

400.

4094

0.41

720.

4205

0.00

330.

4375

1 ⁄2

–13

or0.

5000

–13

UN

C1A

0.00

150.

4985

0.48

22..

.0.

4485

0.44

110.

0074

000.

4069

1B0.

417

0.43

40.

4500

0.45

970.

0097

0.50

002A

0.00

150.

4985

0.48

760.

4822

0.44

850.

4435

0.00

4965

0.40

692B

0.41

70.

434

0.45

000.

4565

0.00

650.

5000

3A0.

0000

0.50

000.

4891

...

0.45

000.

4463

0.00

3700

0.40

843B

0.41

700.

4284

0.45

000.

4548

0.00

480.

5000

1 ⁄2

–16

or0.

5000

–16

UN

2A0.

0014

0.49

860.

4892

...

0.45

800.

4533

0.00

4678

0.42

422B

0.43

20.

446

0.45

940.

4655

0.00

610.

5000

(7)

3A0.

0000

0.50

000.

4906

...

0.45

940.

4559

0.00

3500

0.42

563B

0.43

200.

4420

0.45

940.

4640

0.00

460.

5000

1 ⁄2

–20

or0.

5000

–20

UN

F1A

0.00

130.

4987

0.48

65..

.0.

4662

0.45

980.

0064

000.

4392

1B0.

446

0.45

70.

4675

0.47

590.

0084

0.50

002A

0.00

130.

4987

0.49

06..

.0.

4662

0.46

190.

0042

880.

4392

2B0.

446

0.45

70.

4675

0.47

310.

0056

0.50

003A

0.00

000.

5000

0.49

19..

.0.

4675

0.46

430.

0032

000.

4405

3B0.

4460

0.45

370.

4675

0.47

170.

0042

0.50

00

1 ⁄2

–28

or0.

5000

–28

UN

EF2A

0.00

110.

4989

0.49

24..

.0.

4757

0.47

200.

0036

680.

4564

2B0.

461

0.47

00.

4768

0.48

160.

0048

0.50

003A

0.00

000.

5000

0.49

35..

.0.

4768

0.47

400.

0028

000.

4575

3B0.

4610

0.46

760.

4768

0.48

040.

0036

0.50

00

1 ⁄2

–32

or0.

5000

–32

UN

2A0.

0010

0.49

900.

4930

...

0.47

870.

4752

0.00

3475

0.46

182B

0.46

60.

474

0.47

970.

4842

0.00

450.

5000

3A0.

0000

0.50

000.

4940

...

0.47

970.

4771

0.00

2600

0.46

283B

0.46

600.

4719

0.47

970.

4831

0.00

340.

5000

9 ⁄16

–12

or0.

5625

–12

UN

C1A

0.00

160.

5609

0.54

37..

.0.

5068

0.49

900.

0078

000.

4617

1B0.

472

0.49

0.50

840.

5186

0.01

020.

5625

2A0.

0016

0.56

090.

5495

0.54

370.

5068

0.50

160.

0052

250.

4617

2B0.

472

0.49

00.

5084

0.51

520.

0068

0.56

253A

0.00

000.

5625

0.55

11..

.0.

5084

0.50

450.

0039

000.

4633

3B0.

4720

0.48

430.

5084

0.51

350.

0051

0.56

25

9 ⁄16

–16

or0.

5625

–16

UN

2A0.

0014

0.56

110.

5517

...

0.52

050.

5158

0.00

4725

0.48

672B

0.49

50.

509

0.52

190.

5280

0.00

610.

5625

(7)

3A0.

0000

0.56

250.

5531

...

0.52

190.

5184

0.00

3500

0.48

813B

0.49

500.

5041

0.52

190.

5265

0.00

460.

5625

9 ⁄16

–18

or0.

5625

–18

UN

F1A

0.00

140.

5611

0.54

80..

.0.

5250

0.51

820.

0068

000.

4949

1B0.

502

0.51

50.

5264

0.53

530.

0089

0.56

252A

0.00

140.

5611

0.55

24..

.0.

5250

0.52

050.

0045

470.

4949

2B0.

502

0.51

50.

5264

0.53

230.

0059

0.56

253A

0.00

000.

5625

0.55

38..

.0.

5264

0.52

300.

0034

000.

4963

3B0.

5020

0.51

060.

5264

0.53

080.

0044

0.56

25

(7)

9 ⁄16

–20

or0.

5625

–20

UN

2A0.

0013

0.56

120.

5531

...

0.52

870.

5244

0.00

4280

0.50

172B

0.50

80.

520

0.53

000.

5356

0.00

560.

5625

(7)

3A0.

0000

0.56

250.

5544

...

0.53

000.

5268

0.00

3200

0.50

303B

0.50

800.

5161

0.53

000.

5342

0.00

420.

5625

(7)

9 ⁄16

–24

or0.

5625

–24

UN

EF2A

0.00

120.

5613

0.55

41..

.0.

5342

0.53

020.

0039

600.

5117

2B0.

517

0.52

70.

5354

0.54

050.

0051

0.56

25(7

)3A

0.00

000.

5625

0.55

53..

.0.

5354

0.53

240.

0030

000.

5129

3B0.

5170

0.52

440.

5354

0.53

930.

0039

0.56

25

11




Tabl

e2

Lim

its

ofSi

zefo

rSt

anda

rdSe

ries

Thre

ads

(UN

/UN

R)(C

ont’

d)

Exte

rnal

[Not

e(1

)]In

tern

al[N

ote

(1)]

Pitc

hD

iam

eter

and

UN

RM

inor

Func

tion

alD

iam

eter

Pitc

hD

iam

eter

and

Dia

met

er,

Maj

orD

iam

eter

[Not

e(4

)]M

inor

Func

tion

alD

iam

eter

Ser

ies

Max

.M

ajor

Dia

met

er[N

ote

(4)]

Nom

inal

Siz

ean

dD

esig

-M

ax.

Min

.M

ax.

Tole

ranc

e[N

ote

(6)]

Dia

met

er,

Thre

ads/

in.

nati

onCl

ass

Allo

wan

ce[N

ote

(2)]

Min

.[N

ote

(3)]

[Not

e(2

)]M

in.

[Not

e(5

)](R

ef.)

Clas

sM

in.

Max

.M

in.

Max

.To

lera

nce

Min

.

9 ⁄16

–28

or0.

5625

–28

UN

2A0.

0011

0.56

140.

5549

...

0.53

820.

5345

0.00

3715

0.51

892B

0.52

40.

532

0.53

930.

5441

0.00

480.

5625

3A0.

0000

0.56

250.

5560

...

0.53

930.

5365

0.00

2800

0.52

003B

0.52

400.

5301

0.53

930.

5429

0.00

360.

5625

(7)

9 ⁄16

–32

or0.

5625

–32

UN

2A0.

0011

0.56

140.

5554

...

0.54

110.

5376

0.00

3522

0.52

422B

0.52

90.

536

0.54

220.

5468

0.00

460.

5625

3A0.

0000

0.56

250.

5565

...

0.54

220.

5396

0.00

2600

0.52

533B

0.52

900.

5344

0.54

220.

5456

0.00

340.

5625

(7)

5 ⁄8

–11

or0.

6250

–11

UN

C1A

0.00

170.

6233

0.60

51..

.0.

5643

0.55

600.

0083

000.

5150

1B0.

527

0.54

60.

5660

0.57

670.

0107

0.62

50(7

)2A

0.00

170.

6233

0.61

120.

6052

0.56

430.

5588

0.00

5501

0.51

502B

0.52

70.

546

0.56

600.

5732

0.00

720.

6250

3A0.

0000

0.62

500.

6129

...

0.56

600.

5619

0.00

4100

0.51

673B

0.52

700.

5391

0.56

600.

5714

0.00

540.

6250

5 ⁄8

–12

or0.

6250

–12

UN

2A0.

0016

0.62

340.

6120

...

0.56

930.

5639

0.00

5443

0.52

422B

0.53

50.

553

0.57

090.

5780

0.00

710.

6250

3A0.

0000

0.62

500.

6136

...

0.57

090.

5668

0.00

4100

0.52

583B

0.53

500.

5463

0.57

090.

5762

0.00

530.

6250

5 ⁄8

–16

or0.

6250

–16

UN

2A0.

0014

0.62

360.

6142

...

0.58

300.

5782

0.00

4769

0.54

922B

0.55

70.

571

0.58

440.

5906

0.00

620.

6250

3A0.

0000