ASME B1.30-2002 pdf download
ASME B1.30-2002 pdf download.SCREW THREADS: STANDARD PRACTICE FOR CALCULATING AND ROUNDING DIMENSIONS.
The purpose of ASME B1.30 is to establish uniform and specific practices for calculating and rounding the numeric values used for inch and metric screw thread dcsign data dimensions only. No attempt is made to establish a policy of rounding actual thread characteristics measured by the manufacturer or user of thread gages. Covered is the Standard Rounding Policy regarding the last figure or decimal place to be retained by a numeric value and the number of decimal places to be retained by values used in intermediate calculations of thread design data dimensions. Values calculated to this Standard for inch and metric screw thread design data dimensions may vary slightly from values shown in existing issues of ASME Bi screw thread standards and are to take precedence in all new or future revisions of ASME 131 standards as applicable except as noted in para. 1.2.
1.2 MetrIc Application
Allowances (fundamental deviations) and tolerances for metric M and MJ screw threads are based upon formulas, which appear in applicable standards. Values of allowances for standard tolerance positions and values of tolerances for standard tolerance grades are tabulated in these standards for a selection of pitches. Rounding rules specified below have not been applied to these values but have followed practices of the International Organization for Standardization (ISO). For pitches, which are not included in the tables, standard formulas and the rounding rules specified herein are applicable.
NOTE: ISO rounding practices, for screw thread tolerances and allowances, use rounding to the nearest values in the R40 series of numbers in accordance with ISO 3. in some cases, the rounded values have been adjusted to produce a smooth progression. Since the ISO rounded values have been standardized internationally, for metric screw threads, it would lead to confusion if tolerances and allowances were recalculated using 81.30 rules, for use in the USA. 81.30 rounding rules are, therefore, only applicable to special threads where tabulated values do not exist in ISO standards. Values calculated using the ISO R40 series values may differ from those calculated using B1.30. In such a case the special thread values generated using B1.30 take precedence.
(a) Minor Diameter Exceptions for Internal Threads:
(1) Minimum Minor Diameter. All classes arc calcukited and then rounded off to the nearest 0.001 in. and expressed in three decimal places for sizes 0.138 in, and larger. For Class 3B, a zero is added to yield four decimal places.
(2) Maximum Minor Diameter. All classes are calcukited before rounding, then rounded for Classes lB and 2B to the nearest 0.001 in. for sizes 0.138 in. and larger. Class 3B values are rounded to four decimal places.
3.1.4 Metric screw threads are dimensioned in millimeters. The final values of pitch diameter, major diameter, minor diameter, allowance and thread element tolerances are expressed to three decimal places.
3.1.5 Values containing multiple trailing zeros out to the required number of decimal places can be expressed by displaying only two of them beyond the last significant digit.
EXAMPLE: 20 threads per inch has a pitch equal to 0.05000000 and can be expressed as 0.0500.
3.2 Examples
The formulas in the examples for inch screw threads in Tables 2, 3,4 and 5 are based on those listed in ASME B1.1, Unified Inch Screw Threads. Tables 2 and 3 are based on a size that when converted from a fraction to a decimal will result in a number that has only four decimal places. Tables 4 and 5 are based on a size that when converted will result in a number with infinite numbers of digits after the decimal point.
The formulas in the examples for metric screw threads in Tables 6, 7, 8 and 9 are based on those listed in ASME B1.13M, Metric Screw Threads. Tables 6 and 7 show the use of the tabulated values for allowances and tolerances (in accordance with ISO 965-I) for the calculation of size limits for standard diameter/pitch combinations listed in both ISO 261 and ASME B1.13M. The constant values differ from those used for inch screw threads, in accordance with the policy of rounding of this Standard, because metric limits of size are expressed to only three decimal places rather than four.
4 THREAD FORM CONSTANTS
For thread form data tables, see Table 10.
