Miniature Screw Threads Machinery's Handbook, 31st Edition
1993
Table 2. Unified Miniature Screw Threads—Design Thread Form
Basis for Minimum Major Diameter Specified in Tables
0.07216878 P
P
P 2
0.32475953 P (0.375 H )
60°
0.48000000 P (0.554 H )
Pitch Line
0.51608439 P 0.596 H
0.32074 P
0.86602540 P ( H )
90°
Axis of Internal Thread
P
0.125 P
0.32475953 P (0.375 H ) 0.48000000 P (0.554 H )
P 2
60°
Pitch Line
0.57259074 P (0.661 H )
0.86602540 P ( H )
Junction of Root Contour and Flank 0.18518149 P
Basis for Maximum Minor Diameter Specified in Tables
90°
Axis of External Thread
Formulas for Design Thread Form (maximum material) a External Thread Internal Thread
Thread Element Symbol Formula
Thread Element
Symbol Formula
0.32476 p Height of engagement
0.52 p 0.556 p
Addendum
h e h n
h as h s F cs r rs
Height
0.60 p 0.125 p 0.158 p (approx)
Height of thread Flat at crest Radius at root
Flat at crest Radius at root
0.27456 p 0.072 p (approx)
F cn r rn
a Metric units (millimeters) are used in all formulas.
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