A turnbuckle, also known as a bottlescrew, is a device consisting of two threaded eye bolts with opposite-handed threads that are screwed into each end of a frame. We can better understand its characteristics and applications by understanding the following about the composition and installation methods of turnbuckles.
When the central frame rotators, the eye bolts are prevented from doing so because the two bolts have opposite-handed threads. This causes the bolts to simultaneously move inwards or outwards.
The tapped holes at each end of the frame must also have opposite-handed threads to accept the bolts. The end with the right-handed thread is usually marked with an R and the end with a left-handed thread is marked with an L.
Typically, turnbuckles are used to adjust the tension in cables and tie rods. These components are available in a wide range of sizes, from small units designed to tension fencing wire, to turnbuckles, weighing several tons that form structural elements of large buildings.
In a tensioning application, both bolts should be fully extended before fitting. The turnbuckle can then be screwed up until the desired tension is achieved. For a turnbuckle to adjust the tension, the bolts must be prevented from rotating while the frame is rotated. This means that some initial twisting of cables may occur until the torque in the cables is sufficient to overcome the friction in the turnbuckle.
However, because of the opposite threads, there’s no need for the cables to become twisted as the turnbuckle is tightened.
The turnbuckle consists of the following parameters:
(1)Thread diameter, with larger threads able to carry higher loads. It should be noted, however, that a 12 mm thread turnbuckle typically has a much lower load limit than a 12 mm eye bolt or a 12 mm diameter cable.
(2)Take up is the total difference in length between the turnbuckle with the threads screwed all of the ways in or out. Take up can be increased by attaching two or more turnbuckles in line.
(3)End fittings may be eye bolts, hooks, or shackles. Shackles may also be referred to as jaw-end fittings. Many turnbuckles have an eye at one end and a shackle at the other. Toggle jaw end fittings allow rotation of the turnbuckle in any direction.
(4)Working load limit should be carefully matched to the application. This is likely to result in turnbuckles with threads of larger diameter than that of cables and eye bolts in the tensioning system.
(5)Turnbuckles are available in galvanized steel for most construction and industrial applications, as well as in stainless steel for use offshore, in critical applications, or in exposed architectural features.
The method to install the turnbuckle
Before the installation of any type of turnbuckle hardware, it is important to know the right and left thread and the Working Load Limit (WLL).
Keep in mind of straightforward steps:
(1) First, unscrew end fittings from the turnbuckle body until completely extended to the full take-up length.
(2) Second, connect end fittings on either end to desired securement point, for eye end and hook end fittings, simply loop it through whatever securement point it will be connected to, as for jaw end fitting, unscrew the bolt from the jaw, place the securement point between the clevis ears (thimble, eye bolt, etc), then place the bolt through, and screw it shut.
Different sizes and types of turnbuckles have different workloads and use if you want to know more about this. Terada has extensive experience in hardware and can provide you with some professional advice.
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