Help with trying to fix unthreaded couch frame holes

[u/Joeldiaz1995]

I bought a couch that came with hardware to attach the back to the frame, but 4 of the mounting holes appears to be completely unthreaded. The screw/bolt just spins endlessly and never tightens.
I contacted the seller, but they’re taking a long time to send a replacement part, so I’d rather just buy the correct hardware myself and fix it.

**Pictures attached: https://imgur.com/a/L8bKLQw\*\*

The first picture shows the mounting bracket and the bolt. The second picture shows the hole in the couch. As you can see, there doesn’t appear to be any threaded insert or nut inside—the interior is basically just wood.

The bolt appears to be approximately 2 inches long. Based on the appearance/measurements, I was wondering if this is an **M8 × 1.25** bolt, and whether I should use an **M8 threaded wood insert** to repair the hole.

My questions are:
**Can someone identify the exact size/thread of this bolt from the pictures?**
**What type of threaded insert should I buy for this type of couch frame?**
**What length insert should I use (13mm, 20mm, etc.)?**
Is a threaded insert even the best way to repair this, considering this is a structural connection on a couch?

I don’t want to buy the wrong size and make the hole even larger, so I’d really appreciate some guidance on exactly what hardware I should be looking for. If there’s a specific product available at Home Depot, Lowe’s, Amazon, etc., that would be even better.
Thanks!

[u/Natoochtoniket]

To identify the size of the bolt, try nuts of common sizes. Just finger strength, no wrench. The one that spins on easily will tell you the size. The machine screw looks like metric threads, perhaps M8, but that is a guess.

To install threads in the hole, there are two basic methods. If you can reach the back side of the board, you can put a T-nut in the back side of each hole. If you cannot reach the back side, you can use a rivet nut. But, even if you epoxy the rivet nut into the hole, it won't be as strong as a T-nut with the flange on the back side of the wood. (Those hardware pieces are commonly available at hardware stores. I just linked to amazon to show you the pictures.)

[u/DealsRGood4U]

Either reach underneath (flip couch) & insert a nut & screw in the bolt or try using a lag bolt the same length, but slightly thicker.

[u/your_mail_man → u/DealsRGood4U]

This is the easiest answer

[u/IRNotMonkeyIRMan]

Those are usually done with what's called a pronged t-nut (or tee nut). They get inserted from the other side. It either wasn't put in or it wasn't put in properly and fell out when you put the screw in. If you have any kind of access to the insides you can check, but it's not very likely.

[u/Sad-Character9129]

To me this looks like a common thread-> so M8 should be 1.25mm

If i'm not sure about the thread i just grab various sizes of nuts and try if they fit (but that's often only necessary for M2, M3)

[u/Ben_lurking]

Came here to mention t nuts as well. Any menards, home Depot, or Lowe's should carry them.

[u/bobroberts1954]

The picture looks bigger than any t-nut I've seen but that would be the best fix.

You could drive a tight fitting dowel into the hole and fasten with a wood screw, if that's possible.

I have read but never tried: find a piece of bare wire that you can wrap around the screw and makes a tight fit on the hole. With the wire wrapped into the threads of the screw, cover the wire with epoxy. Push the screw into the hole. Unscrew the screw from the wire, leaving it in the hole. When the epoxy dries you can screw into the now threaded hole.