Machinery's Handbook, 31st Edition
Miniature Screws
1787
Table 3. Miniature Screws - 100 ° Flat Head ASA B18.11-1961, R2010
H
L
L T
T
100 0 + 2 0
A
A V
J
D
UNM THREAD ASA B1.10
TO MINOR DIA . MIN .
45 Ο + 0 o - 5 o
Head Dimensions
D Basic Major Dia.
Av at Full Cone a at max. H
J Slot Width
T Slot Depth
R Radius b
A Head Dia.
H Head Hgt
Size Desig- nation
Thds per Inch
Max. Max. Min. Max. Min. Max. Min. Max. Min. Max. 30 UNM 318 0.0118 0.023 0.021 0.0285 0.007 0.005 0.004 0.003 0.004 0.002 0.005 35 UNM 282 0.0138 0.025 0.023 0.0305 0.007 0.005 0.004 0.003 0.004 0.002 0.005 40 UNM 254 0.0157 0.029 0.027 0.0348 0.008 0.006 0.005 0.003 0.005 0.003 0.006 45 UNM 254 0.0177 0.033 0.031 0.0392 0.009 0.007 0.005 0.003 0.005 0.003 0.006 50 UNM 203 0.0197 0.037 0.035 0.0459 0.011 0.008 0.006 0.004 0.006 0.004 0.008 55 UNM 203 0.0217 0.041 0.039 0.0503 0.012 0.009 0.006 0.004 0.006 0.004 0.008 60 UNM 169 0.0236 0.045 0.043 0.0546 0.013 0.010 0.008 0.005 0.008 0.005 0.010 70 UNM 145 0.0276 0.051 0.049 0.0610 0.014 0.011 0.008 0.005 0.008 0.005 0.010 80 UNM 127 0.0315 0.056 0.054 0.0696 0.016 0.012 0.010 0.007 0.010 0.006 0.012 90 UNM 113 0.0354 0.062 0.058 0.0759 0.017 0.013 0.010 0.007 0.010 0.006 0.012 100 UNM 102 0.0394 0.072 0.068 0.0847 0.019 0.015 0.012 0.008 0.012 0.008 0.016 110 UNM 102 0.0433 0.082 0.078 0.0957 0.022 0.018 0.012 0.008 0.012 0.008 0.016 120 UNM 102 0.0472 0.092 0.088 0.1068 0.025 0.020 0.016 0.012 0.016 0.010 0.020 140 UNM 85 0.0551 0.103 0.097 0.1197 0.027 0.022 0.016 0.012 0.016 0.010 0.020 Bold face type indicates preferred sizes. See Notes for Table 1 through Table 4 on page 1786. a Av derived from maximum D , maximum H , and mean angle. b Relative to maximum major diameter. Specifications.— Head Height: The head heights given in the dimensional tables represent the metal measurement (after slotting). Depth of Slots: The depth of slots on fillister, pan and binding head screws is measured from the bearing surface to the intersection of the bottom of the slot with the head diameter. On heads with a conical bearing surface, the depth of slots is measured parallel to the axis of the screw from the flat top surface to the intersection of the bottom of the slot with the bearing surface. The maximum permissible concavity of the slot shall not exceed 3 percent of the mean head diameter. Bearing Surface: The bearing surface of fillister, pan and binding head screws shall be at right angles to the axis of the body within 2°. Eccentricity: Eccentricity is defined as one half of the total indicator reading. Head Eccentricity: The heads of miniature fastening screws shall not be eccentric with the screw bodies by more than 2 percent of the maximum head diameter or 0.001 inch, whichever is the greater. Eccentricity of Slots: Slots in miniature fastening screw heads shall not be eccentric with screw bodies by more than 5 percent of the nominal body diameter.
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