Miniature Screws Notes for Table 1 through Table 4 Machinery's Handbook, 31st Edition
1786
Material: Corrosion resistant steels: ASTM Designation A276 CLASS 303, COND A
CLASS 416, COND A, heat treat to approx 120,000–150,000 PSI (28–34 on Rockwell C scale) CLASS 420, COND A, heat treat to approx 220,000–240,000 PSI (50–53 on Rockwell C scale) Brass: Temper half hard ASTM Designation B16 Nickel Silver: Temper hard ASTM Designation B151, Alloy C Machine Finish: Machined surface roughness of heads shall be approximately 63 μ in. arithmetical average determined by visual comparison. Applied coatings: Corrosion resistant steel: passivate; Brass: bare, black oxide, or nickel flash. Nickel silver: none Notes: 1) The diameter of the unthreaded body shall not be more than the maximum major diameter nor less than the minimum pitch diameter of the thread. 2) For screw lengths four times the major diameter or less, thread length ( L T ) shall extend to within two threads of the head bearing surface. Screws of greater length shall have complete threads for a minimum of four major diameters. 3) Screws shall be free of all projecting burrs, observed at 3 × magnification. 4) All dimensions are in inches. Table 2. Miniature Screws - Pan Head ASA B18.11-1961, R2010
H
L
T
C
L T
A J
D
UNM THREAD ASA B1.10
TO MINOR DIA . MIN .
45 Ο + 0 o - 5 o
45 Ο + 0 o - 5 o
Pan Head Dimensions
D Basic Major Dia., Max.
A Head Dia.
H Head Hgt
J Slot Width
T Slot Depth a
C Chamfer
R Radius b
Size Desig- nation
Thds per Inch
Max. Min. Max. Min. Max. Min. Max. Min. Min. 30 UNM 318 0.0118 0.025 0.023 0.010 0.008 0.005 0.003 0.005 0.003 0.002 0.002 35 UNM 282 0.0138 0.029 0.027 0.011 0.009 0.005 0.003 0.006 0.004 0.002 0.002 40 UNM 254 0.0157 0.033 0.031 0.012 0.010 0.006 0.004 0.006 0.004 0.002 0.002 45 UNM 254 0.0177 0.037 0.035 0.014 0.012 0.006 0.004 0.007 0.005 0.002 0.002 50 UNM 203 0.0197 0.041 0.039 0.016 0.013 0.008 0.005 0.008 0.006 0.003 0.002 55 UNM 203 0.0217 0.045 0.043 0.018 0.015 0.008 0.005 0.009 0.007 0.003 0.002 60 UNM 169 0.0236 0.051 0.049 0.020 0.017 0.010 0.007 0.010 0.007 0.004 0.003 70 UNM 145 0.0276 0.056 0.054 0.022 0.019 0.010 0.007 0.011 0.008 0.004 0.003 80 UNM 127 0.0315 0.062 0.058 0.025 0.021 0.012 0.008 0.012 0.009 0.005 0.004 90 UNM 113 0.0354 0.072 0.068 0.028 0.024 0.012 0.008 0.014 0.011 0.005 0.004 100 UNM 102 0.0394 0.082 0.078 0.032 0.028 0.016 0.012 0.018 0.014 0.006 0.005 110 UNM 102 0.0433 0.092 0.088 0.036 0.032 0.016 0.012 0.018 0.014 0.006 0.005 120 UNM 102 0.0472 0.103 0.097 0.040 0.035 0.020 0.015 0.020 0.016 0.008 0.006 140 UNM 85 0.0551 0.113 0.107 0.045 0.040 0.020 0.015 0.022 0.018 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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