Class 5 Interference-Fit Threads Torques and Interferences

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Class 5 Interference-Fit Threads Torques and Interferences

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Torques, Interferences, and Engagement Lengths for Class 5 Interference-Fit Threads

Reference: ASME B1.12-1987 (R2013)

Nominal Size	Interference on Pitch Diameter		Engagement Lengths, External Thread Lengths and Tapped Hole Depths¹						Torque at 1-1⁄4D Engagement in Ferrous Material
	Interference on Pitch Diameter		In Brass and Ferrous			In Nonferrous Except Brass			Torque at 1-1⁄4D Engagement in Ferrous Material
	Max	Min	L_e	T_s	T_h min	L_e	T_s	T_h min	Max, lb-ft	Min, lb-ft
0.2500-20	.0055	.0003	0.312	0.375 + .125 − 0	0.375	0.625	0.688 + .125 − 0	0.688	12	3
0.3125-18	.0065	.0005	0.391	0.469 + .139 − 0	0.469	0.781	0.859 + .139 − 0	0.859	19	6
0.3750-16	.0070	.0006	0.469	0.562 + .156 − 0	0.562	0.938	1.031 + .156 − 0	1.031	35	10
0.4375-14	.0080	.0008	0.547	0.656 + .179 − 0	0.656	1.094	1.203 + .179 − 0	1.203	45	15
0.5000-13	.0084	.0010	0.625	0.750 + .192 − 0	0.750	1.250	1.375 + .192 − 0	1.375	75	20
0.5625-12	.0092	.0012	0.703	0.844 + .208 − 0	0.844	1.406	1.547 + .208 − 0	1.547	90	30
0.6250-11	.0098	.0014	0.781	0.938 + .227 − 0	0.938	1.562	1.719 + .227 − 0	1.719	120	37
0.7500-10	.0105	.0015	0.938	1.125 + .250 − 0	1.125	1.875	2.062 + .250 − 0	2.062	190	60
0.8750- 9	.0016	.0018	1.094	1.312 + .278 − 0	1.312	2.188	2.406 + .278 − 0	2.406	250	90
1.0000- 8	.0128	.0020	1.250	1.500 + .312 − 0	1.500	2.500	2.750 + .312 − 0	2.750	400	125
1.1250- 7	.0143	.0025	1.406	1.688 + .357 − 0	1.688	2.812	3.094 + .357 − 0	3.095	470	155
1.2500-7	.0143	.0025	1.562	1.875 + .357 − 0	1.875	3.125	3.438 + .357 − 0	3.438	580	210
1.3750-6	.0172	.0030	1.719	2.062 + .419 − 0	2.062	3.438	3.781 + .419 − 0	3.781	705	250
1.5000-6	.0172	.0030	1.875	2.250 + .419 − 0	2.250	3.750	4.125 + .419 − 0	4.125	840	325

¹L_e = Length of engagement.
T_s = External thread length of full form thread.
T_h = Minimum depth of full form thread in hole.

Maximum Interference

Minimum Interference

Friction between the nut, bolt head or washer may need to be determined as part of specifying an accurate fastener torque.

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.