Threads and Threading - Sportpilot.info

1828 ACME SCREW THREADS
Table 1. American National Standard General Purpose Acme Screw Thread Form
— Basic Dimensions ASME/ANSI B1.5-1997
Thds.
per
Inch
n
Pitch,
P = 1/n
Machinery's Handbook 27th Edition
Height of
Thread
(Basic),
h = P/2
Total
Height of
Thread,
h s = P/2 + 1 ⁄ 2
allowance a
Thread
Thickness
(Basic),
t = P/2
Crest of
Internal Thread
(Basic),
F cn = 0.3707P
Width of Flat
Root of Internal
Thread, F rn
0.3707P −0.259 ×
allowance a
16 0.06250 0.03125 0.0362 0.03125 0.0232 0.0206
14 0.07143 0.03571 0.0407 0.03571 0.0265 0.0239
12 0.08333 0.04167 0.0467 0.04167 0.0309 0.0283
10 0.010000 0.05000 0.0600 0.05000 0.0371 0.0319
8 0.12500 0.06250 0.0725 0.06250 0.0463 0.0411
6 0.16667 0.08333 0.0933 0.08333 0.0618 0.0566
5 0.20000 0.10000 0.1100 0.10000 0.0741 0.0689
4 0.25000 0.12500 0.1350 0.12500 0.0927 0.0875
3 0.33333 0.16667 0.1767 0.16667 0.1236 0.1184
21 ⁄ 2 0.40000 0.20000 0.2100 0.20000 0.1483 0.1431
2 0.50000 0.25000 0.2600 0.25000 0.1853 0.1802
11 ⁄ 2 0.66667 0.33333 0.3433 0.33333 0.2471 0.2419
11 ⁄ 3 0.75000 0.37500 0.3850 0.37500 0.2780 0.2728
1 1.00000 0.50000 0.5100 0.50000 0.3707 0.3655
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 ASME/ANSI B1.5-1997
D = Basic Major Diameter and Nominal Size, in Inches.
P = Pitch = 1 ÷ Number of Threads per Inch.
E = Basic Pitch Diameter = D − 0.5P
K = Basic Minor Diameter = D − P
No. External Threads (Screws)
1 Major Dia., Max. = D
2 Major Dia., Min. = D minus 0.05Pa 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 finerpitches.
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
12 Minor Dia., Max. = Minor Dia., Min. (Formula 11) plus 0.05Pa 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.
Copyright 2004, Industrial Press, Inc., New York, NY