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Class 5 Interference-Fit Threads ANSI/ASME B1.12

ANSI ASME Hardware Design Guide

External Thread Dimensions for Class 5 Interference-Fit Threads ANSI/ASME B1.12-1987 (R1998). The following thread detail specifications are typical for stud applications.

Data within design chart is based on external threaded members being steel ASTM A-325 (SAE Grade 5) or better. L_e = length of engagement.

The following thread designations are used on engineering drawing specifications to distinguish the American Standard Class 5 Threads from the tentative Class 5 and alternate Class 5 threads, specified in Handbook FED H28.

They also distinguish between external and internal American Standard Class 5 Threads.

Class 5 External Threads are designated as follows:

• NC-5 HF—For driving in hard ferrous material of hardness over 160 BHN.
• NC-5 CSF—For driving in copper alloy and soft ferrous material of 160 BHN or less.
• NC-5 ONF—For driving in other nonferrous material (nonferrous materials other than copper alloys), any hardness.

Class 5 Internal Threads are designated as follows:

• NC-5 IF—Entire ferrous material range.
• NC-5 INF—Entire nonferrous material range.

Nominal	Major Diameter, Inches						Pitch Diameter, Inches		Minor Diameter, Inches
	NC-5 HF for driving in ferrous material with hardness greater than 160 BHN Le = 1 1⁄4 Diameter		NC-5 CSF for driving in brass and ferrous material with hardness equal to or less than 160 BHN Le = 1-1/4 Diameter		NC-5 ONF for driving in nonferrous except brass (any hardness) Le = 2 - 1/2 Diameter
Size	Max	Min	Max	Min	Max	Min	Max	Min	Max
.2500–20	.2470	.2418	.2470	.2418	.2470	.2418	.2230	.2204	.1932
.3125–18	.3080	.3020	.3090	.3030	.3090	.3030	.2829	.2799	.2508
.3750–16	.3690	.3626	.3710	.3646	.3710	.3646	.3414	.3382	.3053
.4375–14	.4305	.4233	.4330	.4258	.4330	.4258	.3991	.3955	.3579
.5000–13	.4920	.4846	.4950	.4876	.4950	.4876	.4584	.4547	.4140
.5625–12	.5540	.5460	.5575	.5495	.5575	.5495	.5176	.5136	.4695
.6250–11	.6140	.6056	.6195	.6111	.6195	.6111	.5758	.5716	.5233
.7500–10	.7360	.7270	.7440	.7350	.7440	.7350	.6955	.6910	.6378
.8750– 9	.8600	.8502	.8685	.8587	.8685	.8587	.8144	.8095	.7503
1.0000– 8	.9835	.9727	.9935	.9827	.9935	.9827	.9316	.9262	.8594
1.1250– 7	1.1070	1.0952	1.1180	1.1062	1.1180	1.1062	1.0465	1.0406	.9640
1.2500– 7	1.2320	1.2200	1.2430	1.2312	1.2430	1.2312	1.1715	1.1656	1.0890
1.3750– 6	1.3560	1.3410	1.3680	1.3538	1.3680	1.3538	1.2839	1.2768	1.1877
1.5000– 6	1.4810	1.4670	1.4930	1.4788	1.4930	1.4788	1.4089	1.4018	1.3127