Machinery's Handbook, 31st Edition
Löwenherz Threads
2119
Löwenherz Thread
Diameter
Approximate No. of Threads per Inch
Diameter
Approximate No. of Threads per Inch
Pitch, Millimeters
Pitch, Millimeters
Millimeters
Inches 0.0394 0.0472 0.0551 0.0669 0.0787 0.0905 0.1024 0.1181 0.1378 0.1575 0.1772 0.1968 0.2165 0.2362 0.2756
Millimeters
Inches 0.3543 0.3937 0.4724 0.5512 0.6299 0.7087 0.7874 0.8661 0.9450 1.0236 1.1024 1.1811 1.2599 1.4173 1.5748
1.0 1.2 1.4 1.7 2.0 2.3 2.6 3.0 3.5 4.0 4.5 5.0 5.5 6.0 7.0 8.0
0.25 0.25 0.30 0.35 0.40 0.40 0.45 0.50 0.60 0.70 0.75 0.80 0.90 1.00 1.10 1.20
101.6 101.6 84.7 72.6 63.5 63.5 56.4 50.8
9.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0 36.0 40.0
1.30 1.40 1.60 1.80 2.00 2.20 2.40 2.80 2.80 3.20 3.20 3.60 3.60 4.00 4.40
19.5 18.1 15.9 14.1 12.7 11.5 10.6 9.1
42.3 36.3 33.9 31.7 28.2 25.4 23.1 21.1
9.1 7.9 7.9 7.1 7.1 6.4 5.7
0.3150 … Swiss Screw Thread.— This is a thread system originated in Switzerland as a standard for screws used in watch and clock making. The angle between the two sides of the thread is 47 degrees 30 minutes, and the top and bottom of the thread are rounded. This system is used by the British Association as a standard for small screws, and is known as the British Association thread. See British Association Standard Thread (BA) on page 2114. Historical and Miscellaneous Threads … … … Aero-Thread.— The name “Aero-thread” has been applied to a patented screw thread sys- tem that is applicable where the nut or internally threaded part is made from a soft mate - rial, such as aluminum or magnesium alloy, for lightness, as in aircraft construction, and where the screw is made from a high-strength steel to provide strength and good wearing qualities. The nut or part containing the internal thread has a 60-degree truncated form of thread. See Fig. 1 . The screw, or stud, is provided with a semi-circular thread form, as shown. Between the screw and the nut there is an intermediary part known as a thread lining or insert, made in the form of a helical spring, so that it can be screwed into the nut. The stud is then screwed into the thread formed by the semicircular part of the thread insert. When the screw is provided with a V-form of thread, like the American Standard, frequent loosening and tightening of the screw would cause rapid wear of the softer metal from which the nut is made; furthermore, all the threads might not have an even bearing on the mating threads. By using a thread insert which is screwed into the nut permanently and made from a reasonably hard material, good wearing qualities are obtained. Also, the bearing or load is evenly distributed over the threads of the nut since the insert, being in the form of a spring, can adjust itself to bear on all the thread surfaces. Boss or Nut
Thread Insert
Screw or Stud
Fig. 1. The Basic Thread Form Used in the Aero-Thread System
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