Interference-Fit Threads Machinery's Handbook, 31st Edition
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Table 3. Torques, Interferences, and Engagement Lengths for Class 5 Interference-Fit Threads ANSI/ASME B1.12-1987 (R2018)
Engagement Lengths, External Thread Lengths and Tapped Hole Depths a
Torque at 1- 1 ∕ 4 D Engagement in Ferrous Material
Interference on Pitch Diameter
In Brass and Ferrous
In Nonferrous Except Brass
Nominal Size 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 Max Min L e T s T h min L e T s T h min Max, lb-ft 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 a L e = Length of engagement. T s = External thread length of full form thread. T h = Minimum depth Materials for Externally Threaded Products: The length of engagement, depth of thread engagement and pitch diameter in Table 1, Table 2, and Table 3 are designed to produce adequate torque conditions when heat-treated medium-carbon steel products, ASTM A325 (SAE Grade 5) or better, are used. In many applications, case-carburized and non- heat-treated medium-carbon steel products of SAE Grade 4 are satisfactory. SAE Grades 1 and 2 may be usable under certain conditions. This standard is not intended to cover the use of products made of stainless steel, silicon bronze, brass or similar materials. When such materials are used, the tabulated dimensions will probably require adjustment based on pilot experimental work with the materials involved. of full form thread in hole. All dimensions are inches. Lubrication: For driving in ferrous material, a good lubricant sealer should be used, particularly in the hole. A non-carbonizing type of lubricant (such as a rubber-in-water dispersion) is suggested. The lubricant must be applied to the hole and it may be applied to the male member. In applying it to the hole, care must be taken so that an excess amount of lubricant will not cause the male member to be impeded by hydraulic pressure in a blind hole. Where sealing is involved, the lubricant selected should be insoluble in the medium being sealed. For driving, in nonferrous material, lubrication may not be needed. The use of medium gear oil for driving in aluminum is recommended. American research has observed that the minor diameter of lubricated tapped holes in nonferrous materials may tend to close in, that is, be reduced in driving; whereas with an unlubricated hole the minor diameter may tend to open up. Driving Speed: This standard makes no recommendation for driving speed. Some opin ion has been advanced that careful selection and control of driving speed is desirable to obtain optimum results with various combinations of surface hardness and roughness. Experience with threads made to this standard may indicate what limitations should be placed on driving speeds.
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