Screw and Washer Assemblies-SEMS (Inch Series)
Screw and Washer Assemblies - SEMS (Inch Series)
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CONTENTS
Foreword ivCommittee Roster ACorrespondence With the B18 Committee vi2 Introduction . General Data 11 13 Data for Helical Spring Lock Washer SEMS 124 Data for Tooth Lock Washer SEMS 135 Data for Conical Spring Washer SEMS. 13Data for Plain Washer SEMS. 14
Figures
Unthreaded Length on Screws With Machine Screw Thread DiameterPitchUnthreaded Length on Tapping Screws With Spaced Thread Diameter-Pitch Combinations 112 Combinations 113 4 Enlarged Conical Spring Washer Section and Tooth Washer Dimensions Verification of Bearing Width on Helical Spring Lock Washers 13 145 Conical Spring Washer Twist Test 15
Tables
1 Dimensions of Helical Spring Lock Washers for Socket Head Cap Screw SEMS2 Dimensions of Helical Spring Lock Washers for SEMS With Machine and Tapping Screws Having Machine Screw Thread Diameter-PitchDimensions of Helical Spring Lock Washers for SEMS With Screws Having CombinationsType B Tapping Screw Thread DiameterPitch Combinations5 Dimensions of Internal Tooth Lock Washers for SEMS Dimensions of Extermal Tooth Lock Washers for SEMS ....6 7 Dimensions of Conical Spring Washers for SEMS Dimensions of Plain Washers for SEMS
Nonmandatory Appendix
A Relative Proportions of Screw Heads and Plain or Conical Spring Washers 17
FOREWORD
American National Standards Committee B27 for the standardization of plain and lock washersStandards Association (later the United States of America Standards Institute and as of October 6 was organized in March 1926 as Sectional Committee B27 under the aegis of the American1969 the American National Standards Institute Inc.) with the Society of Automotive Engineers and the American Society of Mechanical Engineers as joint sponsors. Since 1950 this Committehas also been assigned responsibility for standardization of washers and machine rings.) Thecarry on development work: Submittee 1 on plain washers and Submittee 2 on lock Committe was reorganized in May 1928 at which time two submittees were established towashers.
In 1940 the B27 Committee was reactivated and Submittee 2 proceeded to draft a proposalcovering helical spring lock washer. It was further amended in 1943 and following approval by the B27 Committe and sponsor organizations accepted as an American Standard under thedesignation ASA B27.1-1994.
applicable tohelical spring lock washers made from materials other than carbon steel and included A draft proposal pleted by Submitte 2 in September 1949 incorporated requirementsscrew assemblies. Subsequent to approval by the B27 Committee and sponsors this proposal specifications for tooth lock washers both helical spring and tooth lock washers and machinewas forwarded to the American Standards Association and declared an American Standard on May 22 1950.
During the years 1951 through 1956 Submittee 2 considered numerous refinements to theeees ss blies.A formal draft dated June 1957 was approved by letter ballot of theB27Committe andthe sponsor organizations and submitted to the American Standards Association for designation
as an American Standard. This was granted on November 3 1958.
that the screw and washer assemblies monly known as SEMS be published as a separate In 1961 a study group prised of members of the B18 and B27 Commiees remendeddocument under the jurisdiction of the B18 Commitee but subject to approval of both SectionalCommittees and theaffected submittes thereof.This remendationwas accepted by the B27 and B18 Committees respectively on the 28th and 30th of November 1961. Submittee 272
At the initial meeting of Submittee 27 on February 1 1962 a proposal was submittedconsisting of pertinent data for lock washer SEMS extracted from ASA B27.1-1958 and for plain washer SEMS proposed for inclusion in ASA B27.2 plus information gleaned fromSAE Standard J773 Conical Spring Washers. It was agreed that the proposal should be extendedto include tapping screw SEMS. Consequently aditional meetings of the submittee were held at which new drafts incorporating data for these products were reviewed and further changesand corrections were remended. On February 15 1963 a formal proposal was circulated for ment to Submittees 3 9 and 27 of the B18 Committee and Submittees 1 and 2 ofthe B27 Committee. On November 15 1963 a revised draft incorporating resolutions to the ments received and additional refinements was letter balloted to Sectional Committees B18and B27. The resulting ments and disapprovals were resolved at a meeting of SectionalCommittee B18 on June 4 1964 and by circulation of the remended dispositions to Sectional
