What is a Turnbuckle?

About This Video

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Video Transcription

Hi, I’m Brad from Tenshon, and this video is about turnbuckles.

I’m going to show you the parts of a turnbuckle, explain how it works and demonstrate installing one. Here I have two turnbuckles, one is assembled and one is disassembled so you can more easily see the parts. There’s a body, two eye bolts and two lock nuts. As you can see these eye bolts are welded shut. Eye bolts that are welded are optimal because they are stronger, allowing for higher working loads. Not all turnbuckles have eye bolts that are welded shut.

Here I have a turnbuckle with the eyes not welded. Other turnbuckles have hooks instead of eyes. The best turnbuckles have eyes that are welded shut. Other turnbuckles with unwelded eyes are more likely to fail under load.

A turnbuckle works because the two eye bolts have opposite threads. One is a conventional thread with right to tighten and left to loosen, and the other eye bolt is a reverse thread, left to tighten, right to loosen.

Because they have opposite threads, when the main body is turned, the eye bolts are either drawn in together or pushed away from each other.

Let me show you what would happen if both sides had conventional threads.

Here I have a coupler nut and two conventional bolts. If I hold the bolt and turn the coupler nut, it simply moves the coupler up and down the bolts.

Now that you have an understanding of what a turnbuckle is and how it works, I’m going to show you how to install one.

When installing a turnbuckle you’ll use a D shackle on each end. As you perhaps guessed, this gets its name from its shape, since it looks like a capital D. The D shackle has two parts, the body and the pin. The body has two holes, one that’s unthreaded and one that’s threaded. The pin goes through the unthreaded hole first, and then threads into the second hole.

You’ll have an issue if you try and install it the other direction, as the threads will thread, but it will hit a stop.

To begin, remove the pin from the D shackle. Loop the D shackle through the corner of the sail, making sure the shackle passes around both the D ring and the wire rope. Take the turnbuckle and push it between both arms of the D shackle, then, reinsert the pin.

Once the D ring is attached to the sail, you’ll attach the D ring to the other side. In this case we’ll be attaching to a pull tab.

Once again, remove the pin from the D shackle. Place the D shackle through one of the holes on the pull tab, and then insert the eye bolt between the two holes, and reinsert the pin.

The pin needs to be more than hand tight, so you’ll need to use a wrench to tighten it. Use an adjustable wrench like this one to tighten the pins on the D shackles.

The pins need to be snug but be careful not to over tighten them. If you over tighten them, you run the risk of locking up the threads and the pin will be stuck.

Once the turnbuckle is attached at both ends you’ll need to tighten it, to do this use a wrench. Make sure that the wrench is large enough to cover both sides of the body of the turnbuckle. This wrench is too small, notice how it doesn’t fully grab both sides of the body.

When tightening a turnbuckle, don’t use a screwdriver inserted into the two halves of the body. This puts stress on the two halves of the body separately and can damage it. Both sides need to be turned in unison.

At a minimum, you’ll need to tighten the turnbuckle until the threaded eyes extend into the body.

Here, you can see the threads extend into the body.

Sails work best when they’re tight, so it’s important to continue tightening the turnbuckle, even after the eye bolts have entered the body. It’s normal to feel some resistance as the sail stretches.

The turnbuckles I’ve shown so far have not been greased, and that’s to keep things a bit cleaner here in the studio. It’s very important that your turnbuckles are properly greased to prevent binding or seizing. Here’s a turnbuckle that’s been greased using white lithium grease.

We have a full video about greasing turnbuckles. The link to that video can be found in the description below. Be sure to check that video out after you watch this video.

After the turnbuckle is fully tightened, you’ll need to lock it in place by tightening the two lock nuts. Use a wrench to hold the body in place.

Use a second wrench to tighten the lock nut. This step is very important as it prevents the turnbuckle from backing off and becoming disconnected.

If you need added security you can use a length of non-corrosive wire. Loop the wire through the body of the turnbuckle and through the D shackle, then twist it off.

That’s it for today’s video. Thanks for watching. If you have any questions leave them in the comments below.

As always, for more information, visit tenshon.com.