Centralizing Acme Screw Threads Machinery's Handbook, 31st Edition
2063
0.0945 P max
45 °
Internal Thread (Nut)
P 4
P 4
External Thread (Screw)
Fig. 2. Disposition of Allowances, Tolerances, and Crest Clearances for General Purpose Single-start Acme Threads (All Classes)
Thread Form: The thread form is the same as the General Purpose Acme Thread and is shown in Fig. 3 . The formulas in Table 7 determine the basic dimensions, which are given in Table 6 for the most generally used pitches. Angle of Thread: The angle between the sides of the thread measured in an axial plane is 29 degrees. The line bisecting this 29-degree angle shall be perpendicular to the axis of the thread. Chamfers and Fillets: External threads have the crest corners chamfered at an angle of 45 degrees with the axis to a minimum depth of P /20 and a maximum depth of P /15. These modifications correspond to a minimum width of chamfer flat of 0.0707 P and a maximum width of 0.0945 P (see Table 6, columns 6 and 7). External threads for Classes 2C, 3C, and 4C may have a fillet at the minor diameter not greater than 0.1 P Thread Series: A series of diameters and pitches is recommended in the Standard as preferred. These diameters and pitches have been chosen to meet present needs with the fewest number of items in order to reduce to a minimum the inventory of both tools and gages. This series of diameters and associated pitches is given in Table 9.
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