Machinery's Handbook, 31st Edition
Miniature Screws
1785
Slotted Head Miniature Screws The ASA B18.11 standard establishes head types, their dimensions, and lengths of slot ted head miniature screws, threaded in conformance with American Standard Unified Miniature Screw Threads, ASA B1.10. The standard covers threads of a nominal diameter from 0.0118 inch (0.3 mm) to 0.0551 inch (1.4 mm). Preferred diameter pitch combina tions for general use are shown in bold type in the tables. Head Types.— Fillister Head: The fillister head has a flat top surface (oval crown optional) with cylindrical sides and a flat bearing surface. The head proportions are given in Table 1. Pan Head: The pan head has a flat top surface, cylindrical sides, and a flat bearing sur face. The head height is less than the fillister but the head diameter is slightly larger. Head proportions are given in Table 2. Flat Head: The flat head has a flat top surface and a conical bearing surface with an included angle of approximately 100°. Head proportions are given in Table 3. Binding Head: The head height is less than the pan head but the head diameter is greater, and is intended for applications which would otherwise require washers. Head proportions are given in Table 4. Table 1. Miniature Screws - Fillister Head ASA B18.11-1961, R2010
H
L
T
C
L T
D
A J
UNM THREAD ASA B1.10
TO MINOR DIA . MIN .
45 Ο + 0 o - 5 o
OVAL CROWN OPTIONAL MIN. RADIUS 0.85 OF NOMINAL HEAD DIA.
Fillister Head Dimensions
D Basic Major Dia.
A Head Dia.
C Chamfer
R Radius b
J Slot Width
T Slot Depth a
H Head Hgt
Size Desig- nation
Thds per Inch
Max. Max. Min. Max. Min. Max. Min. Max. Min. Min. 30 UNM 318 0.0118 0.021 0.019 0.012 0.010 0.004 0.003 0.006 0.004 0.002 0.002 35 UNM 282 0.0138 0.023 0.021 0.014 0.012 0.004 0.003 0.007 0.005 0.002 0.002 40 UNM 254 0.0157 0.025 0.023 0.016 0.013 0.005 0.003 0.008 0.006 0.002 0.002 45 UNM 254 0.0177 0.029 0.027 0.018 0.015 0.005 0.003 0.009 0.007 0.002 0.002 50 UNM 203 0.0197 0.033 0.031 0.020 0.017 0.006 0.004 0.010 0.007 0.003 0.002 55 UNM 203 0.0217 0.037 0.035 0.022 0.019 0.006 0.004 0.011 0.008 0.003 0.002 60 UNM 169 0.0236 0.041 0.039 0.025 0.021 0.008 0.005 0.012 0.009 0.004 0.003 70 UNM 145 0.0276 0.045 0.043 0.028 0.024 0.008 0.005 0.014 0.011 0.004 0.003 80 UNM 127 0.0315 0.051 0.049 0.032 0.028 0.010 0.007 0.016 0.012 0.005 0.004 90 UNM 113 0.0354 0.056 0.054 0.036 0.032 0.010 0.007 0.018 0.014 0.005 0.004 100 UNM 102 0.0394 0.062 0.058 0.040 0.035 0.012 0.008 0.020 0.016 0.006 0.005 110 UNM 102 0.0433 0.072 0.068 0.045 0.040 0.012 0.008 0.022 0.018 0.006 0.005 120 UNM 102 0.0472 0.082 0.078 0.050 0.045 0.016 0.012 0.025 0.020 0.008 0.006 140 UNM 85 0.0551 0.092 0.088 0.055 0.050 0.016 0.012 0.028 0.023 0.008 0.006 Bold face type indicates preferred sizes. See Notes for Table 1 through Table 4 on page 1786. a T measured from bearing surface. b Relative to maximum major diameter. Max.
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