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AS 3635-1990
[Current]Unified (ISO inch) screw threads, associated gauges, and gauging practice
Specifies requirements for parallel screw threads having the Unified thread form for the diameter size range No. 0 (0.060 in) to 6 in inclusive. Limits of size for the Unified coarse, fine, extra fine, and constant pitch screws and a supplementary series of Unified threads of diameter greater than 6 in are given. It also covers screw gauges, associated check and setting gauges, and plug gauges with information being given on types of gauges, materials and hardness, general gauge design requirements, marking, and general notes on inspection of screw threads. Appendices give the basis of tabulated values, examples for calculating the limits of size of untabulated screw threads, notes on the production of external threads, notes on pitch and flank angle errors, notes on recommended system for gauging coated threads, and the limiting dimension of screw gauges for the more commonly used Unified threads.
Published: 12/11/1990
Pages: 136
Table of contents
Cited references
Content history
Table of contents
Header
About this publication
PREFACE
1 SCOPE AND GENERAL
1.1 SCOPE
1.2 APPLICATION
1.3 THE UNIFIED SCREW THREAD SYSTEM
1.4 REFERENCED DOCUMENTS
1.5 NOTATION
2 SCREW THREAD PROFILES
2.1 SCOPE OF SECTION
2.2 BASIC PROFILE AND THREAD DATA
2.3 MAXIMUM MATERIAL (DESIGN) PROFILE
2.3.1 Maximum material (design) profile—internal thread
2.3.2 Maximum material (design) profile—external thread
2.4 LIMITING PROFILES
2.5 ROOT CONTOURS
2.5.1 Internal threads
2.5.2 External threads
3 GENERAL PLAN
3.1 SCOPE OF SECTION
3.2 THREAD SERIES
3.2.1 General
3.2.2 Coarse pitch series (UNC) threads
3.2.3 Fine pitch series (UNF) threads
3.2.4 Extra fine pitch series (UNEF) threads
3.2.5 Constant pitch series
3.3 SELECTION OF DIAMETER/PITCH COMBINATIONS
3.4 BASIC DIMENSIONS
4 THREAD CLASSES, DEVIATIONS, AND TOLERANCES
4.1 SCOPE OF SECTION
4.2 FUNDAMENTAL DEVIATIONS
4.3 TOLERANCES
4.3.1 General
4.3.2 Pitch diameter tolerances
4.3.3 Crest diameter tolerances
4.3.4 Root diameter tolerances
4.4 THREAD CLASSES
4.4.1 General
4.4.2 Recommended combinations
4.4.2.1 General
4.4.2.2 Thread classes 1A and 1B
4.4.2.3 Thread classes 2A and 2B
4.4.2.4 Thread classes 3A and 3B
4.5 LENGTH OF AXIAL THREAD ENGAGEMENT
4.5.1 General
4.5.2 UNC, UNF, 4 UN, 6 UN and 8 UN threads
4.5.3 UNEF, 12 UN, 16 UN, 20 UN, 28 UN, 32 UN and UNS threads
4.6 COATED THREADS
4.6.1 General
4.6.2 External threads
4.6.2.1 Class 1A
4.6.2.2 Class 2A
4.6.2.3 Class 2AG
4.6.2.4 Class 3A
4.6.3 Internal threads
5 LIMITS OF SIZE
5.1 SCOPE OF SECTION
5.2 LIMITS OF SIZE
6 DESIGNATION
6.1 UNCOATED THREADS
6.2 COATED THREADS
6.3 THREADS WITH SPECIAL REQUIREMENTS
6.3.1 Threads with non-standard lengths of axial thread engagement
6.3.2 Thread with modified crests
7 GAUGING OF UNIFIED SCREW THREADS
7.1 SCOPE OF SECTION
7.2 TYPES OF GAUGES
7.2.1 Gauges for external threads and associated check and setting plugs
7.2.1.1 Screw gauges
7.2.1.2 Associated check and setting gauges
7.2.2 Gauges for internal threads
7.3 MATERIALS AND HARDNESS
7.3.1 Materials
7.3.2 Hardness
7.4 REFERENCE TEMPERATURE
7.5 MARKING
7.6 INSPECTION OF SCREW THREADS
7.6.1 General considerations
7.6.2 Gauging of screw threads
7.6.2.1 General
7.6.2.2 Gauging of external threads
7.6.2.3 Gauging of internal threads
7.6.3 Gauge wear
7.6.4 Disputes
7.7 DESIGN FEATURES OF SCREW GAUGES
7.7.1 General construction
7.7.1.1 Gauge blanks and handles
7.7.1.2 Gauging surfaces
7.7.1.3 Axial length of gauge thread
7.7.2 Breaking of sharp edges
7.7.2.1 General
7.7.2.2 Feather edges
7.7.3 Dirt grooves
7.7.4 Thread profiles
7.7.4.1 GO screw gauges and GO screw check plugs
7.7.4.2 NOT GO screw gauges and NOT GO screw check plugs
7.7.4.3 GO screw check plugs for solid NOT GO screw ring gauges
7.7.4.4 Double and single length setting plug gauges
7.8 LIMITS OF SIZE OF GAUGING ELEMENTS
7.8.1 General
7.8.2 Deviations for GO Screw plug gauges
7.8.3 Deviations for NOT GO screw plug gauges
7.8.4 Deviations for GO and NOT GO plain plug gauges
7.8.5 Deviations for GO solid screw ring gauges
7.8.6 Deviations for NOT GO solid screw ring gauges
7.8.7 Deviations for GO screw check plugs for solid GO screw ring gauges
7.8.8 Deviations for NOT GO screw check plugs for new solid GO screw ring gauges
7.8.9 Deviations for NOT GO screw check plugs for worn solid GO screw ring gauges
7.8.10 Deviations for GO screw check plugs for solid NOT GO ring gauges
7.8.11 Deviations for NOT GO screw check plugs for NOT GO solid screw ring gauges
7.8.12 Deviations for GO and NOT GO plain check plugs for GO and NOT GO solid screw ring gauges
7.8.13 Deviations for adjustable GO screw ring and calliper gauges
7.8.14 Deviations for adjustable NOT GO screw ring and calliper gauges
7.8.15 Deviations for double length setting plugs for adjustable GO screw ring gauges
7.8.16 Double length setting plugs for adjustable NOT GO screw ring gauges
7.8.17 Deviations for single length setting plugs for adjustable GO screw calliper gauges
7.8.18 Deviations for single length setting plugs for adjustable NOT GO screw calliper gauges
7.8.19 Deviations for GO and NOT GO plain calliper gauges
7.8.20 Values for use in calculating gauge dimensions
APPENDIX A
A1 SCOPE
A2 DIAMETERS
A2.1 Vulgar fractional inch diameters
A2.2 Decimal fractional inch diameters
A3 PITCHES
A4 DESIGNATION
A5 DEVIATIONS AND TOLERANCES
A6 LIMITS OF SIZE
APPENDIX B
B1 SCOPE
B2 TOLERANCE GRADES
B2.1 Pitch diameter tolerances
B3 CREST DIAMETER TOLERANCES
B3.1 Major diameter tolerances for external threads
B3.2 Minor diameter tolerances for internal threads
B4 ROOT DIAMETER TOLERANCES
B4.1 Minor diameter tolerances for external threads
B4.2 Major diameter tolerances for internal threads
B5 FUNDAMENTAL DEVIATIONS
B6 LENGTH OF AXIAL THREAD ENGAGEMENT (Le)
B6.1 External threads
B6.2 Internal threads
B7 DEPTH OF RADIAL ENGAGEMENT
APPENDIX C
C1 NOTATION
C2 DATA FOR CALCULATION OF CLASSES 1A, 2A, AND 3A EXTERNAL THREADS—UNCOATED
C3 DATA FOR CALCULATION OF CLASSES 1B, 2B and 3B INTERNAL THREADS—UNCOATED
C4 DETAILED EXAMPLES
C4.1 Example 1
C4.2 Example 2
C4.3 Example 3
APPENDIX D
APPENDIX E
E1 SCOPE
E2 THE PRINCIPLE OF GAUGING
E2.1 General
E2.2 The Taylor Principle
E2.3 Permissible departures from the Taylor Principle
E3 FUNCTION AND USE OF GAUGES
E3.1 Gauges for external threads
E3.1.1 Solid and adjustable GO screw ring gauges
E3.1.2 Solid and adjustable NOT GO screw ring gauges
E3.1.3 Adjustable GO screw calliper gauges
E3.1.4 Adjustable NOT GO screw calliper gauges
E3.1.5 GO and NOT GO plain ring and calliper gauges
E3.2 Gauges for internal threads
E3.2.1 GO screw plug gauges
E3.2.2 NOT GO screw plug gauges
E3.2.3 GO and NOT GO plain plug gauges
E3.3 Setting and check plug gauges
E3.3.1 Single length setting plug gauges
E3.3.2 Double length setting plug gauges
E3.3.3 Screw check plug gauges
E3.3.4 NOT GO wear check plug gauges
E3.3.5 GO and NOT GO plain plug gauges
E4 CHECKING (VERIFICATION) OF GAUGES
APPENDIX F
F1 SCOPE
F2 DEFINITIONS
F3 EFFECT OF PITCH AND FLANK ANGLE ERRORS
F3.1 General
F3.2 Effect of errors in pitch
F3.3 Effect of errors in flank angles
F4 COMBINATION OF PITCH AND FLANK ANGLE ERRORS
APPENDIX G
G1 SCOPE
G2 RECOMMENDED SYSTEM OF GAUGING EXTERNAL THREADS BEFORE AND AFTER COATING
G2.1 External threads with specified allowances which have to be maintained after coating—Unified threads, Class 1A
G2.2 External screw threads with specified allowances (in the uncoated condition) which may be absorbed by the coating—Unified threads, Class 2A
G2.3 External screw threads with no specified allowance—Unified threads, Class 3A
G.3 RECOMMENDED SYSTEM OF GAUGING INTERNAL THREADS BEFORE AND AFTER COATING
G3.1 Unified threads, Classes 1B and 2B
G3.2 Unified threads, Class 3B
G4 SUMMARY OF GAUGES FOR CHECKING UNIFIED THREADS
APPENDIX H
H1 SCOPE
H2 MANUFACTURING RECOMMENDATIONS
H3 SETTING GO AND NOT GO ADJUSTABLE SCREW RING GAUGES
H3.1 General
H3.2 Setting GO and NOT GO adjustable screw ring gauges using double length setting plugs
APPENDIX I
I1 SCOPE
I2 UNIFIED COARSE THREAD SERIES (UNC)—SIZE RANGE 1/4 in TO 4 in (INCLUSIVE)
I3 UNIFIED FINE THREAD SERIES (UNF)—SIZE RANGE 1/4 in TO 1 1/2 in (INCLUSIVE)
I4 UNIFIED EXTRA FINE THREAD SERIES (UNEF)—SIZE RANGE 1/4 in TO 1 11/16 in (INCLUSIVE)
Cited references in this standard
Content history
DR 87198
AS 3635-1990 REC:2017
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