FINAL December 20, 2006 A Guide for the Development of ASME B18 Standards for Mechanical Fasteners ASME B18.12.1 - 2006 Key Words: Guide, B18 Standards FINAL: December 20, 2006 Sponsored and Published By THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS Three Park Avenue New York, N.Y. 10016-5990ASME BI8,12.1-2006 GUIDE BI8 STANDARDSGUIDE BIS STANDARDS ASME 18,12.1-2006 A GUIDE FOR THE DEVELOPMENT OF ASME B18 STANDARDS FOR MECHANICAL FASTENERS, 1, Introductory Notes 11 Scope This guide covers the elements forthe com- plete development of B18 standards. It should be understood that only those clements applicable to the development of any given standard should be adopted. Clearly, not all may be reasonably ap- plied to any given standard. ‘The discussion ofthe clements is presented in the order they would nor- mally appear in a given B18 standard and a tem- plate is included in Appendix A. 1.2 Comparison to ISO Standards ‘Where ISO standards exist, a detailed com- parison to the ASME metric standard, including each geometric characteristic, material, range of size, and performance is suggested to facilitate specification byrespective users. The detail of comparison should be included in an appendix while this paragraph in the standard identifies the ISO standards for com- parative purposes and refers to the appendix fora detailed summary by applicable characteristic, A good example of this comparison may be found in Appendix IV of ASME B18.2.3.1M. Also, an ex- ample taken from B18.2.3.4M is included in Ap- pendix B of this standard for illustrative purposes. 1.3 Dimensions A statement indicating that: "unless other- wise specified, all dimensions are in inches" or that “all dimensions, unless otherwise specified, are in met- ric (mm)" should be included. Itis recommended that standards be written only in inch or only in met- ric (mm) and that dual dimensions be avoided. This is intended to provide a basis for possible global acceptance of purely metric documents, All dimen- sions shall apply before coating and this statement should be included to prevent confusion regarding any dimensional changes that may occur as a result of coating, 1.4 Options ‘This paragraph is intended to offer flexibility to the application of the standard. For example, where special materials, coatings, lubrication, ot packaging may be needed by the purchaser, this provision should be included in the standard and specified by the purchaser on the purchase order. 1.5 Terminology ‘This paragraph is intended to reduce the ver- biage in each standard and o focus ona single docu- ment, namely, ASME B18.12, to provide for con- sistency in definitions that may have formerly ap- peared in multiple standards with slight variations. Where terms are not defined in ASME B18.12, they are included and defined in this paragraph. 15.1 Terminology Referenced For definitions of terminology not specifi- cally defined inthis standard, refer o ASME B18.12. 1.6 Referenced Standards ‘This paragraph is intended to identify all stan- dards that are specified or referred to in a given stan-ASME B18,12,1-2006 dard by name, number, and publisher. Itshould also state that the latest edition of the listed standard isto beused, unless specific date of issue is included in the list. Specific dates shall notbe listed, unless a technical engineering reason has been established necessitating the citing of specific issue 1.6.1 Example of Referenced Standards Standards that are called out should be listed by issuing source. The most current issue of the referenced standard is applicable, unless otherwise specified by the purchaser. Below is an example: Example: Referenced Standards Unless otherwise specified, the standards referenced shall be the most recent at the time of order placement. ASME B11, Unified Inch Screw Threads (UN and UNR Thread Form) ASME BI8.12, Glossary of Terms for Me- chanical Fasteners ASME BI8.18.1, Inspection and Quality As- surance for General Purpose Fasteners ASME BI8.18.2, Inspection and Quality As- surance for High-Volume Machine As- sembly Fasteners ASME B18.24, Part Identifying Number (PIN) Code System for B18 Fastener Products Publisher: The American Society of Me- chanical Engineers (ASME Interna- tional), Three Park Avenue, New York, NY 10016-5990; Order Department: 22 Law Drive, Box 2300, Fairfield, NJ 07007-2300 ASTM B21, Specification for Naval Brass, Rod, Bar, and Shapes GUIDE BIS STANDARDS ASTM FII37, Specification for Phosphate! Oil and Phosphate/Organic Corrosion Protective Coatings for Fasteners ASTM FI941, Specification for Electrode- posited Coatings on Threaded Fasten- ers [Unified Inch Screw Threads (UN/ UNR)] Publisher: American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428 1.7 Related Standards This may list standards and their sources that are not referred to in the given document but may cover similar or related products or tests. For ex- ample, a spring pin standard may list related stan- dards for other pins such as clevis, cotter, or dowel. pins. These would be listed ina similar way as shown in paragraph 1.6.1. 1.8 PartIdentifying Number This isa standard "boiler plate” paragraph torefer the specification user to ASME B18.24 and recommended procedure to establish a part iden- tification number (PIN) applicable to all B18 prod- uct standards, typically, paragraph 1.8: For a Part Identifying Number, refer to ASME B18.24. 2, General Data This paragraph provides for specification of geometry, materials and heat treatment, dimensional conformance, quality assurance, workmanship, gag- ing and acceptance procedures, marking require- ments, and packaging. A review of the template in- cluded in Appendix A of this guide will help to iden- tify, fora given product, which of the features should necessarily be included.GUIDE BIS STANDARDS 2.1 Heads ‘The intention of this paragraph isto describe and identify the head configuration and its dimen- sions and tolerances. A drawing is usually present and the dimensions are identified by letters which are included with a word description in tables to- gether with stated dimensions and tolerances. These should be specific so that wrench or driver fitis as- sured, Inthose produets such as pins or studs, which have no head configuration, this paragraph should not be applied. A list of seventeen head character- isties which may be included as appropriate in sub- paragraphs are listed in Appendix A. The following isan example of typical head characteristics: Example. 2.1.1 Top of Head. Top of head shall be full form and chamfered or rounded with the diameter of chamfer circle or start of rounding being equal to the maximum width across flats within a tolerance of minus 15%, 2.1.2 Width Across Flats. The width across flats of heads shall be the distance, measured perpendicular to the axis of prod- uct, overall between two opposite sides of the head. 213 Head Taper. across flats shall not be exceeded. No transverse section through the head be- tween 25% and 75% of actual head height, as measured from the bearing surface, shall be less than the minimum width across flats. Maximum width 214 Head Height. The head height shall be that overall distance measured ASME 18,12.1-2006 parallel to the axis of the product from the top of the head to the bearing surface and shall include the thickness of the washer face, Raised grade and manufacturer's iden- Lification are excluded from head height. 2.1.5 True Position of Head. The axis of the head shall be located at true posi- tion with respect to the axis of the body (determined over a distance under the head equal to one diameter) within a tolerance zone having a diameter equivalent to 6% of the maximum width across flats at maxi- ‘mum material condition. 2.2 Product Length This paragraph would normally define the overall product length and tolerances, which are stan- dard, anda procedure for measurement. Addition- ally, such lengths as the thread length (2.5), grip gag- ing length, body length, and transition thread length (2.6) are often included as subparagraphs to assist in selection and application, Example: The length of the screw shall be mea- sured parallel to the axis of the screw from the plane of the bearing surface under the head to the plane of the flat of the point. 2.3 Threads ‘Most threads are specified by reference to ASMEBI.1 or ASMEBI.13M including a given pitch anda class of fit. Methods relating to accept- ability are identified asa given system in ASME B13, and a separate paragraph (2.4) would be used to specify the thread acceptance system. The follow- ing is typical paragraph for thread specification:ASME B18,12,1-2006 Example. 24 Threads shall be cut or rolled in ac- cordance with ASME BI.1, Unified Coarse, Class 2A. Thread Acceptance Gaging Typically, this paragraph would specify thread dimensional acceptability in accordance with, Gaging Sy tem 21 as specified in ASME B1.3 or ASME B1.3M for metric product, However, the user may have specified certain thread characteris- tics which will require a different acceptance proce- dure and this paragraph will usually state System 21, unless otherwise specified. Example: 25 Unless otherwise specified by the pur- chaser, gaging for screw thread dimen- sional acceptability shall be in accor- dance with Gaging System 21 as speci- fied in ASME B1.3M. Thread Length Thread length is controlled on many bolts by the so-called grip gaging length maximum, This paragraph will specify this, if applicable, and sub- paragraphs will specify the method or procedure for ‘measurement, Ci tain small produets, suchas ma- chine screws, may specify the thread length in terms ofits approach to the bearing surface of the head by the number of thread pitches. Example: 2.5.1 Machine Screws. Machine screws shall have thread lengths conforming to the following: On screws threaded full length, the distance to first full form thread shall be ‘measured, parallel to the axis of screw, from GUIDE BIS STANDARDS the bearing surface of the head to the face of @ nonchamfered or noncounterbored standard 34 GO thread ring gage assembled by hand as far as the thread will permit (a) Sizes No. 5 and Smaller, Screws of ‘nominal lengths equal to three diameters and shorter shall have full form threads extend- ing to within one pitch (thread) of the bear- ing surface of the head, or closer, if practi- cable. Nominal lengths greater than three diameters, up to and including 1-1/8 in., shall have full form threads extending to within two pitches (threads) of the bearing surface of the head, or closer, if practicable. Screws of longer nominal lengths shall, un- less otherwise specified, have a minimum length of full form thread of 1 in (b) Sizes No. 6 and Larger. Screws of nominal lengths equal to three diameters and shorter shall have full form threads extend- ing to within one pitch (thread) of the bear- ing surface of the head, or closer, if practi- cable. Nominal lengths greater than three diameters, up to and including 2 in., shall have full form threads extending to within two pitches (threads) of the bearing surface of the head, or closer, if practicable. Screws of longer nominal lengths shall, unless oth- erwise specified, have a minimum length of full form thread of 1.50 in 2.5.2 Body Length Body length isthe distance, as measured par- allel to the axis of the fastener, fiom the underside of the head to the last scratch of thread or top of the extrusion angle. 2.5.3 Grip Gaging Length This is the distance as measured parallel to the axis of the fastener from the underside of theGUIDE BIS STANDARDS head bearing surface to the face of a noncounter- bored or noncountersunk standard Go thread ring gage which has been assembled by hand as far as the thread will permit. 2.6 [ransition Thread Length A dimension commonly expressed asa refer- cence dimension which accounts forthe length of in- complete threads, extrusion angle for rolled threads, and the tolerances on the grip length. It is recom- ‘mended that both a rolled and cut thread represen- tation be present for each threaded product as may be applicable, Often, the transition thread length may be expressed as the number of pitches for a given thread. 2.7 Point All screws have a point to facilitate starting or to apply pressure (compression). Such points are called out as flat, oval, cup, cone, or half dog. In other cases, points are described as chamfered or rounded from a given diameter below the minor thread diameter, and having a length which is amul- tiple of the thread pitch. The length of the point ‘measured to the first full formed thread at the major diameter may be specified in the dimensional table fora given screw. Rivets and pins may have sheared ends or may be crowned or chamfered as specified in the applicable product standard. Point features not defined in a given product standard are at the discretion of the manufacturer. 2.8 Body Diameter This is generally the unthreaded portion ofa shank whose diameter is the maximum or minimum. limit or the basic size with plus and minus tolerances applied. Itis often used to "account" for any swell, fin, or die seam under the head from manufacture. ASME 18,12.1-2006 2.8.1 Reduced meter Body ‘These have a body diameter not less than the minimum pitch diameter, and not exceeding the specified minimum full size diameter body. 2.9 True Position of Tapped Hole The axis of a tapped hole in the mut is lo- cated at true position with respect to the axis of the nut body within a tolerance zone having a diameter equal toa given percentage of the the maximum width across flats. 2.10 Nut Thickness The nut thickness is the overall distance ‘measured parallel to the axis of the mut, from the top of the nut to the bearing surface. This includes the thickness of the washer face where provided. Raised ‘markings are not included in nut thickness. 2.11 Prongs Cotter pins havea preferred point extended prong having a square or hammered lock design unless otherwise specified. 2.12 Taper ‘Taper pins provide for a taper on the diam- eter based on a unit of length and fora given toler ance, 2.13 Straightness A rail gage or a sleeve gage is used to as- sure shank straightness or camber limitations included within respective product standards. At maximum ‘material condition, maximum camber per unit length is generally specitied for given product lengths.ASME B18,12,1-2006 2.14 Finishes Dimensions for products and dimensional characteristics are usually specified for plain finish, Ifa coating is specified, itshould be in accordance witha class or condition specified in an applicable standard such as an ASTM standard, 2.18 Workmanship A clause which assures that a product will be visually free of irregularities that would impact its fit, form, or function. 2.16 Designation This provides a standard method for call out in communications. Example: Product name, ASME dimensional standard, diameter-pitch, length, mechanical or per- formance standard, finish type and thick ness including applicable standard, Examples: Heavy hex mut, ASME BI8.2.6, Unified 1/2 13, ASTM AS63 Grade C, Plain Finish Hex cap screw, ASME B18.2.1, Unified 3/8 16 x 4, ASTM A354 Grade BD, type Fe/Zn- 5A, ASTM 1941 Metric hex cap screws, ASME BI8.2.3.1M, MIG x 2 x 100, ASTM 568M Class 10.9, Plain Finish Metrie hex nuts Style 2, ASME B18.2.4.2M, M10 x 1.5, ASTM AS63M Class 9, Plain Fin: ish GUIDE BIS STANDARDS 2.17 Grade or Property Class Symbol These marks are mandated by the applicable ‘material and performance specification such as those found in ASTM or SAE, Inch series products are generally related to Grades 2, 5,and 8; while metric series products are related to property classes rang- ing from 4.6 to 12.9. Atypical calloutis as follows: Example: Each bolt shall be marked in accordance with the requirements of ASTM A449. 2.18 Manufacturer's or Source Symbol These marks are mandated by the standards that specify material, mechanical, and performance requirements. For fasteners subject to the Fastener Quality Act requirements, the marks used are to be fully traceable and registered by the manufacturer with the U.S, Patent and Trademark Office. This registration is required by the Fastener Quality Act. 2.19 Inspection and Quality Assurance ASME has seven quality assurance docu- ments (ASME BI8.18.1 thru B18.18.7) for me- chanical fasteners. ASTM has a document (ASTM F1470) to determine sample sizes for mechanical properties using detection or prevention techniques. The standard should be called out in this paragraph, which is the most basic for the given product, with the option for altemative specification leftto the pur- chaser. Example: Unless otherwise specified, products shall be furnished in accordance with ASME BIB.18.2.