MODIFIED STUB ACME THREAD FORM 1 (M1)

Recognizing the fact that one Stub Acme thread form may not provide a generally acceptable thread system to meet the requirements of all applications, basic data for two of the other commonly used forms (shown in Figs. A1 and A2) are tabulated inT ables A1 and A2. Wherever practicable, the standard Stub Acme thread form should be used.

In applying the foregoing data to special designs, the allowances and tolerances can be taken directly from Tables 4, 5, and 6 for standard Stub Acme threads. Therefore, the major diameter and basic thread thickness at pitch line for both external and internal threads will be the same as for the standard form, as shownin Tables 3 and 7. The pitch diameter and minor diameterw ill vary from the data shown in Tables 3 and 7. For the Modified Form 1 Stub Acme thread, the pitch and minor diameters will be smaller than similar values for the standard form; and for Modified Form 2 the pitch and minor diameters will be larger than those dimensions for the standard forms.

For gaging these modified Stub Acme threads, the principles of gaging outlined in Section 2 (para. 2.1.3) of this Standard will apply. The dimensions of gages can be calculated from the data in Section 2 (paras. 2.1.1, 2.1.2, and 2.1.4). The gage tolerances should be taken from para2.. 1 and Tables 8, 9, and 10.These threads should be designatedo n drawings as described in para. 1.14 with the insertion after “Acme” of ‘”1” for the Modified Form 1 and“2” for the Modified Form 2.