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Internal Thread Dimensions for Class 5 Interference-Fit Threads

ANSI ASME Hardware Design Guide

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

Data within design chart is based on internall 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 spcifications 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 Size	NC-5 IF Ferrous Material			NC-5 INF Nonferrous Material			Pitch Diameter		Major Diameter
	Minor Diameter		Tap Drill	Minor Diameter		Tap Drill
	Min	Max		Min	Max		Min	Max	Min
.2500–20	.196	.206	.2031	.196	.206	.2031	.2175	.2201	.2532
.3125–18	.252	.263	.2610	.252	.263	.2610	.2764	.2794	.3161
.3750–16	.307	.318	.3160	.307	.318	.3160	.3344	.3376	.3790
.4375–14	.374	.381	.3750	.360	.372	.3680	.3911	.3947	.4421
.5000–13	.431	.440	.4331	.417	.429	.4219	.4500	.4537	.5050
.5625–12	.488	.497	.4921	.472	.485	.4844	.5084	.5124	.5679
.6250–11	.544	.554	.5469	.527	.540	.5313	.5660	.5702	.6309
.7500–10	.667	.678	.6719	.642	.655	.6496	.6850	.6895	.7565
.8750– 9	.777	.789	.7812	.755	.769	.7656	.8028	.8077	.8822
1.0000– 8	.890	.904	.8906	.865	.880	.8750	.9188	.9242	1.0081
1.1250– 7	1.000	1.015	1.0000	.970	.986	.9844	1.0322	1.0381	1.1343
1.2500– 7	1.125	1.140	1.1250	1.095	1.111	1.1094	1.1572	1.1631	1.2593
1.3750– 6	1.229	1.247	1.2344	1.195	1.213	1.2031	1.2667	1.2738	1.3858
1.5000– 6	1.354	1.372	1.3594	1.320	1.338	1.3281	1.3917	1.3988	1.5108

Related:

• Standard Tolerance Limits Fits ANSI B4.1 | GD&T Tolerances
• Class V Locational Interference Tolerance Chart for Holes and Bolts
• Bushing and Plain Bearings Press or Shrink Fit Design and Application
• Cylinder Feature Press Fit Design Equations
• Preferred Force Shrink Fits Chart ANSI B4.1 Calculator