Machinery's Handbook, 31st Edition
ACME SCREW THREADS 2057 Table 1. American National Standard General Purpose Acme Screw Thread Form— Basic Dimensions ANSI/ASME B1.5-1997 (R2014)
Width of Flat
Total Height of Thread, h s = P /2 + 1 ∕ 2 allowance a
Root of Internal Thread, F rn 0.3707 P − 0.259 × allowance a
Thread Thickness (Basic), t = P /2 0.03125 0.03571 0.04167 0.05000 0.06250 0.08333 0.10000
Crest of Internal Thread (Basic), F cn = 0.3707 P
Height of Thread (Basic), h = P /2 0.03125 0.03571 0.04167 0.05000 0.06250 0.08333 0.10000 0.12500 0.16667 0.20000 0.25000 0.33333 0.37500 0.50000
Thds. per Inch n
Pitch, P = 1/ n 0.06250 0.07143 0.08333 0.10000 0.12500 0.16667 0.20000 0.25000 0.33333 0.40000 0.50000 0.66667 0.75000 1.00000
16 14 12 10
0.0362 0.0407 0.0467 0.0600 0.0725 0.0933 0.1100 0.1350 0.1767 0.2100 0.2600 0.3433 0.3850 0.5100
0.0232 0.0265 0.0309 0.0371 0.0463 0.0618 0.0741 0.0927 0.1236 0.1483 0.1853 0.2471 0.2780 0.3707
0.0206 0.0239 0.0283 0.0319 0.0411 0.0566 0.0689 0.0875 0.1184 0.1431 0.1802 0.2419 0.2728 0.3655
8 6 5 4 3
0.12500 0.16667 0.20000 0.25000 0.33333 0.37500 0.50000
2 1 ∕ 2
2
1 1 ∕ 2 1 1 ∕ 3
1
All dimensions are in inches. a Allowance is 0.020 inch for 10 threads per inch and coarser, and 0.010 inch for finer threads. Table 2a. American National Standard General Purpose Acme Single-Start Screw Threads—Formulas for Determining Diameters ANSI/ASME B1.5-1997 (R2014) D = Basic Major Diameter and Nominal Size, in Inches. P = Pitch = 1 ÷ Number of Threads per Inch. 1 Major Dia., Max. = D 2 Major Dia., Min. = D minus 0.05 P a but not less than 0.005. 3 Pitch Dia., Max. = E minus allowance from Table 4. 4 Pitch Dia., Min. = Pitch Dia., Max. (Formula 3) minus tolerance from Table 5. 5 Minor Dia., Max. = K minus 0.020 for 10 threads per inch and coarser and 0.010 for finer pitches. 6 Minor Dia., Min. = Minor Dia., Max. (Formula 5) minus 1.5 × pitch diameter tolerance from Table 5. Internal Threads (Nuts) 7 Major Dia., Min. = D plus 0.020 for 10 threads per inch and coarser and 0.010 for finer pitches. 8 Major Dia., Max. = Major Dia., Min. (Formula 7) plus 0.020 for 10 threads per inch and coarser and 0.010 for finer pitches. 9 Pitch Dia., Min. = E 10 Pitch Dia., Max. = Pitch Dia., Min. (Formula 9) plus tolerance from Table 5. 11 Minor Dia., Min. = K E = Basic Pitch Diameter = D − 0.5 P K = Basic Minor Diameter = D − P No. External Threads (Screws) 12 Minor Dia., Max. = Minor Dia., Min. (Formula 11) plus 0.05 P a but not less than 0.005. a If P is between two recommended pitches listed in Table 3 , use the coarser of the two pitches in this formula instead of the actual value of P .
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