Express Software Production

ThreadSpecs3 ™

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30° Trapezoidal Threads

Trapezoidal threads are metric and similar in purpose to Acme threads, except that their flank angles are 15°, rather than 14.5°.
Like 60° metric threads, they have tolerance classes composed of a grade and position. Only the pitch diameter class is specified.
The tolerance grades are single digit numbers, whereas the positions are letters, capital for internal threads, lowercase for external threads.
The grade indicates the actual tolerance used for pitch diameter, whereas the position indicates a fundamental deviation for the external pitch diameter, which is either zero or negative, and is applied to the basic pitch diameter.
The only grades supported by this software are 7, 8, and 9 for both external and internal threads.
Internal threads always use position H, and have no deviation.
External threads can use position e or c in this software.
Only the pitch diameter class is specified in the thread designation.
The external major diameter always uses class 4h, and the internal minor diameter always uses 4H.

References :
For Trapezoid product threads, see ISO 2901-2016,ISO 2902-2016,ISO 2903-2016, and ISO 2904-2020.
For gages, see DIN 103-9, except for setting rings; for them, refer to ANSI/ASME B1.2-1983 or ANSI/ASME B1.16M-1984.

Tip on using this software : Non-standard sizes

If the pitch diameter tolerance cannot be determined directly from a table in ISO 2903, then the formula is used, where the nominal size is the geometric mean of the matching range of sizes. After the calculation is applied, the nearest "preferred" number is used, based on the R40 series of numbers. For example, if the formula results in a tolerance of .231 mm, the reported tolerance will be .236 .

Gages

Working Thread Rings are used to gage external product threads. The "GO" ring should assemble with the product it is gaging, whereas the "NOT GO" ring should not. Generally, the minimum major diameter is specified, without a tolerance.

Working Thread Plugs are used to gage internal product threads. The "GO" plug should assemble with the product it is gaging, whereas the "NOT GO" plug should not. Generally, the maximum minor diameter is specified, without a tolerance.

Setting Rings are used to set indicating gages for internal product threads. GO rings are used to set gages to the maximum material size, NOT GO for the minimum material size. Generally, the minimum major diameter is specified, without a tolerance.
DIN 103-9 does not specify dimensions for setting rings, so we specify basic dimensions per ANSI/ASME B1.16M-1984, with tolerances specified in DIN 103-9 for setting plugs.

Setting Plugs are used to set indicating gages for external product threads, in addition to adjustable working ring gages. GO plugs are used to set gages to the maximum material size, NOT GO for the minimum material size. Generally, the maximum minor diameter is specified, without a tolerance.