Type AB Screw Thread Specifications and Dimensions

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Thread Dimensions for Type AB Self-tapping Screw Threads - ANSI B18.6.4

Basic Screw Diameter or Nominal Size		Threads Per Inch	D		d		L		Minimum Torsional Strength (Lb In)
			Major Diameter		Minor Diameter		Minimum Practical Screw Length
			Max	Min	Max	Min	90° Heads	Csk Heads
2	.560	32	.088	.082	.064	.060	3/16	7/32	4
4	.1120	24	.114	.108	.086	.082	7/32	9/32	13
5	.1250	20	.130	.123	.094	.090	1/4	5/16	18
6	.1380	20	.139	.132	.104	.099	9/32	11/32	24
7	.1510	19	.154	.147	.115	.109	5/16	3/8	30
8	.1640	18	.166	.159	.122	.116	5/16	3/8	39
10	.1900	16	.189	.182	.141	.135	3/8	7/16	56
12	.2160	14	.215	.208	.164	.157	7/16	21/32	88
1/4	.2500	14	.246	.237	.192	.185	1/2	19/32	142
5/16	.3125	12	.315	.306	.244	.236	5/8	3/4	290
3/8	.3750	12	.380	.371	.309	.299	3/4	29/32	590
* 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. Recommended over a Type A, particularly in brittle materials. Material AISI 1016-1024 oe equivalent steel8 Heat Treatment Steel only - Quenched in liquid and then tempered by reheating to 650°F minimum Case Hardness Rockwell C45 Minimum Case Depth Nos. 4 thru 6 Dia. - .002-.007, Nos. 8 thru 12 dia. - .004 - .009, 1/4" and larger - .005 - .011 Core Hardness Rockwell C28 - C38 after tempering Plating See plating pages