Screw Threads: Standard Practice for Calculating and Rounding Dimensions
|Publication Date:||1 January 2002|
The American National Standards Committee B1 for standardization of screw threads was organized in 1920 as sectional Committee B1 under the sponsorship of the American Engineering Standards Committee (later the American Standards Association, then the United States of America Standards Institute and as of October 6, 1969, the American National Standards Institute, Inc.), with the Society of Automotive Engineers and The American Society of Mechanical Engineers as joint sponsors. As a result, a great deal of effort was expended through the years toward development of several screw thread standards.
Recognizing the need to standardize the method of rounding decimal values in the calculation of screw thread dimemsions, the ASME Standards Committee B1 charged Subcommittee 30 with the responsibility for producing such a standard.
This Standard designated ASME B1.30 was developed only to serve as the basis for rounding of decimal values associated with the computation of screw thread dimensions.
The examples and formulas depicted within this Standard are for reference only and are presented only to clarify the rounding procedures described. When calculating the different thread characteristics for a particular thread form, refer to the appropriate ASME B1 standard for the formulas and methodology of calculation for that thread.
This Standard was originally approved as an American National Standard on June 29, 1992. This issue updates the 1992 issue and includes:
(a) the addition of a note to para. 1.2 for the clarification of the use of this Standard for metric applications;
(b) the addition of an exception in para. 3.1.3 to the number of decimal places for the allowance 2A when used in intermediate calculations as Td2;
(c) the addition of the maximum external UN minor diameter, maximum and minimum internal pitch diameters and the minimum internal major diameter to the example in para. 3.2.1;
(d) removal of Appendix A containing various common values for 60 deg thread elements. This was done because the values are either listed or can be calculated by formulas in other existing B1 standards;
(e) the addition of an example for a standard metric size that is listed in ASME B1.13M and ISO 261;
(f) the addition of an example for a special inch size showing how to round numbers with an infinite number of digits after the decimal point;
(g) added a new Appendix A with a table listing the number of decimal places for each of the thread characteristics used in the examples in B1.30.
Suggestions for improvement of this Standard will be welcome. They should be sent to Secretary, ASME B1 Standards Committee, Three Park Avenue, New York, NY 10016-5990 U.S.A.
This revision was approved as an American National Standard on July 12, 2002.