Type A Screw Thread
Specifications and Dimensions

Note:  Countersunk heads are measured from the top

Thread Dimensions for Type A Self-Tapping Screw Threads
ANSI B18.6.4 - 1998

Basic Screw Diameter
or
Nominal Size
Threads
Per Inch
D d L Minimum
Torsional
Strength
(Lb In)
(Steel
Screws
Only)
Major Diameter Minor Diameter These Lengths or Less
Have AB threads
Max Min Max Min 90° Heads * Csk Heads
6 .1380 .18 .141 .136 .102 .096 1/4 5/16 24
7 .1510 16 .158 .152 .114 .108 5/16 3/8 30
8 .1640 15 .168 .162 .123 .116 3/8 7/16 39
10 .1900 12 .190 .188 .133 .126 3/8 1/2 48
12 .2160 11 .221 .215 .162 .155 7/16 9/16 83
14 .2420 10 .254 .248 .185 .178 1/2 5/8 125
20 .3200 9 .333 .327 .234 .226 11/16 13/16 250
24 .3720 9 .390 .383 .291 .282 3/4 1 492
* Countersunk Bolts and Screws lengths are always measured from the top of the head


  • Advantages For self starting in thin, .015-.050, metal or resin filled plywood. 18-8 Stainless Steel may be used in applications that require more corrosion resistance. Remember that fastening some dis-similar metals, like stainless steel to aluminum, can cause galvanic reactions, electrolysis corrosion, in some environments.
  • Material Steel: AISI 1016-1024 oe equivalent steel, Stainless Steel: Austenitic 18-8
  • Heat Treatment Steel only - Quenched in liquid and then tempered by reheating to 650°F minimum
  • Case Hardness Rockwell C45 Minimum
  • Case Depth Nos. 6 Dia. - .002-.007, Nos. 8 thru 12 dia. - .004 - .009, 1/4" - .005 - .011
  • Core Hardness Rockwell C28 - C38 after tempering
  • Plating See plating pages




Smith Fastener Company • 3613 East Florence Avenue, Bell, California, 90201
Phone: ( 323 ) 587-0382 • FAX: ( 323 ) 587-8712 • E-mail: [email protected]
Copyright © 2009 by Smith Fastener Company

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