Machinery's Handbook, 31st Edition
1788
Miniature Screws Table 4. Miniature Screws - Binding 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
45 Ο + 0 o - 5 o
Binding Head Dimensions
D Basic Major Dia
C Chamfer
R Radius
H Head Hgt
J Slot Width
T Slot Depth a
A Head Dia.
Size Desig- nation
Thds per Inch
Max. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. 40 UNM 254 0.0157 0.041 0.039 0.010 0.008 0.006 0.004 0.005 0.003 0.002 0.004 0.002 45 UNM 254 0.0177 0.045 0.043 0.011 0.009 0.006 0.004 0.006 0.004 0.002 0.004 0.002 50 UNM 203 0.0197 0.051 0.049 0.012 0.010 0.008 0.005 0.006 0.004 0.003 0.004 0.002 55 UNM 203 0.0217 0.056 0.054 0.014 0.012 0.008 0.005 0.007 0.005 0.003 0.004 0.002 60 UNM 169 0.0236 0.062 0.058 0.016 0.013 0.010 0.007 0.008 0.006 0.004 0.006 0.003 70 UNM 145 0.0276 0.072 0.068 0.018 0.015 0.010 0.007 0.009 0.007 0.004 0.006 0.003 80 UNM 127 0.0315 0.082 0.078 0.020 0.017 0.012 0.008 0.010 0.007 0.005 0.008 0.004 90 UNM 113 0.0354 0.092 0.088 0.022 0.019 0.012 0.008 0.011 0.008 0.005 0.008 0.004 100 UNM 102 0.0394 0.103 0.097 0.025 0.021 0.016 10.012 0.012 0.009 0.006 0.010 0.005 110 UNM 102 0.0433 0.113 0.107 0.028 0.024 0.016 0.012 0.014 0.011 0.006 0.010 0.005 120 UNM 102 0.0472 0.124 0.116 0.032 0.028 0.020 0.015 0.016 0.012 0.008 0.012 0.006 140 UNM 85 0.0551 0.144 0.136 0.036 0.032 0.020 0.015 0.018 0.014 0.008 0.012 0.006 Bold face type indicates preferred sizes. See Notes for Table 1 through Table 4 below. a T measured from bearing surface. Underhead Fillets: The radius of the fillet under perpendicular bearing surface type heads shall not exceed 1 ∕ 2 times the pitch of the thread. The radius of the fillet under conical bearing surface type heads shall not exceed 2 times the pitch of the thread. The radius of the fillet under the binding head is given in Table 4. Max. Unthreaded Diameter: On miniature fastening screws not threaded to the head, the diameter of the unthreaded body shall not be more than the maximum major diameter of the thread nor less than the minimum pitch diameter of the thread. Length: The length of miniature screws having perpendicular bearing surface type heads shall be measured from the bearing surface to the extreme end in a line parallel to the axis of the screw. The length of screws with conical bearing surface type heads shall be measured from the top of the head to the extreme end in a line parallel to the axis of the screw. Preferred lengths are those listed in Table 5. Tolerance on Length: The length tolerance of miniature screws shall conform to the limits given in Table 5. Length of Thread: On all miniature screws having a length four times the nominal body diameter or less the threaded length shall extend to within two threads of the bearing sur face of the head. Screws of greater length shall possess complete threads for a minimum of four diameters.
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