Dining Table Chair Repair

Question

Some years ago, I purchased a set of dining table chairs. Alas, despite being happy with them in other ways, they are not well made. After a few months of normal use (pulling them out, sitting in them, scooching forward and back, etc) the legs get wobbly.

The reason is that the legs are held firm only by two bolts, each, as shown below. The bolts go through those crosspieces and into the chair leg itself. When tight, they provide rigidity to the whole structure, but they are the only thing doing so-- the pieces at right angles are just glued on. After normal use, the bolts get loose, the legs get wobbly, and I have to turn them upside down and tighten the nuts with a wrench which is awward due to the positions. (And annoying, because I should not need to provide quarterly maintenance on chairs.)

Question 1: How can I get these things to stay straight? A little locktite, maybe? Where would it be best applied?

The upper image shows what this assembly is supposed to look like, from underneath the seat of the chair. However, I just discovered one of the chairs has a bolt that has completely pulled out of the chair leg, as shown in the lower image. But that bolt (if that's the right term) has nothing to grip on to make driving it in easier. Fingers are just not sufficient.

Question 2: Is there any easy way to get that thing driven deep into the chair leg, other than aligning it and turning the nut quarter-turn by quarter-turn? (In fact, will even that work?)

Answer 1

A lot of good suggestions here already - pack & glue in the cross-members being primary.
On the one where the bolt has pulled out completely, you will also need to pack & glue. You've basically stripped the thread - which is only wood, of course, so setting it back in more firmly is going to help. Fix this back & allow to set fully before re-assembling the rest. While you've got everything apart, it would probably be a good time to pull all those bolts & glue them back, before they suffer the same fate.
i note from comments that there's nowhere to get a wrench on between the threads. In that case borrow a nut from another bolt & lock two nuts together; then you can drive the entire bolt from the rear-most nut.

Part of what causes it to come apart is that the small leverage on each joint gets ironically greater as it works loose, accelerating the process - so the trick is to prevent it starting in the first place.

Packing every joint with slivers of wood & gluing solid will help prevent the initial movement.
Replacing those regular nuts with Nylocks will help prevent them coming loose at all, or get an identical set of nuts & lock them in pairs, like you did to drive the bolts back in, above.

This looks like the perfect job for a drill-driver with a set of deep socket adaptors. Much easier on the wrists & you can get even tension on all the components.

Answer 2

This is a fairly common setup. The bolt is usually a double threaded one with a wood screw at one end and a machine bolt at the other end.

One such example is here (ad from google / walmart)

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These are designed to bite into the wood and hold that end of the leg so that you can tighten it with the machine screw.

However, if your chairs are wobbling, it is often because this screw isn't tight or it has compressed the wood and made the hole bigger. So you can remove the dowel and pack the hole with sawdust, matches, and epoxy and re-install the dowel (pro tip: the center piece can be turned by a wrench).

Your second picture suggests that you might actually have broken the end of the wood screw off in the chair leg, and you'll have to drill it out.

Apart from that, in addition to using a wrench, you can use a long socket. However, overtightening the machine screw just tends to bend the quarter wooden piece forcing the rails apart.

Answer 3

Borrow one of the other nuts and use it to lock them together at the end of the bolt. Tighten the outer nut to spin the whole thing.

Then keep the inner nut from spinning with a second wrench and take the outer one back off.

Answer 4

I had a similar setup. A couple of the legs fell off. My table actually had little triangular blocks but I think were just friction holding against the rails.

I used PL 400 construction adhesive on the joints between the legs and the rails and the blocks and then put the bolts/nuts back on. You've got more to work with than I did. In your case I'd get PL400 and a popsicle stick and apply the adhesive to the rail leg connection.

It is hard to tell what the bolt is screwing into. Sometimes there are furniture connectors that are glued into the hole to receive the bolt. For the bolt that failed I'd throw some adhesive into the hole and get the bolt to bottom out and put the nut on after the glue has setup. Modern adhesives can be stronger than the resin that is holding the wood fibers together - the wood fibers will pull apart before the glue to fiber connections fail.

Answer 5

Buy some toothpicks and wood glue. Stick the toothpicks into the hole and mark where they reach the end of the hole. Cut them, then apply some wood glue and place them in the hole.

Now screw your bolts back in. Give it a day or so to dry.

This works because the toothpick provides more surface to bite to. The wood glue keeps it from working loose easily. This might not be a permanent fix (you're still putting all the stress on the bolts) but it should provide you more stability than you have, and it's a cheap fix for cheap furniture.

Answer 6

Start by putting two nuts on the same bolt. Secure them against each other but not at the wood. Then use a socket or spanner to drive the threaded stud into the wood. The risk here is that you overdrive it and split the leg, then that whole chair is dead.

The stud that has pulled loose has removed the threads with it, so remove it completely along with diagonal plate.
Drill the hole to a larger size and firmly tap home a tight-fitting dowell with wood-glue/PVA as a lubricant. Sometimes it helps to have a small hole drilled down through the bore of the dowell to release air from inside the joint.
Once that is dry and cured, drill through the middle of the dowell with a drill that is no bigger than the minor diameter of the coarse thread.
Roughen the valleys of the course thread with a file, scratch it up to add some tooth.
Add some 2 part epoxy to the thread and drive it home into the leg as per above, back into its original position. Then leave it for at least a day for the epoxy to cure. Then reassemble. You should either use nylock nuts with anti-vibration washers inside, or get double the nuts and use two on each stud such that they are tight against each other.

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I might be tempted to cut an octagonal shape out of 10~12mm ply such that it fills the entire base of the chair, and rests between the two bolts in each corner. Use glue and pocket screws or brads to secure it permanently. This will stiffen the base against racking and separating, but doesn't help to hold the legs on.

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Or I'd accept that the finish will never be right again, and drill from the outside through each leg into the side-piece with a 10mm dowelling bit and then drive home some round wooden dowell. Normally this would be done before assembly, but its already assembled hence the need to do it from the outside.
Looks like you will get 2 dowells placed alternating directions easily, 2+3 would be nicer, or 3 each way would be better again.
When the wood glue is dried and cured (several days) then flush-cut the exposed portion of dowell, file, sand, fill any holes, sand, stain, and varnish.

Your third option might be to disassemble the chair base, and build it again using the same dowelling techniques, but from the inside as it should have been done.
You could also replace the four diagonal stubs with a triangle shaped biscuit, and rebate that into the leg and sides. Downside of this is that its a lot of work and you don't know the quality of the existing wood. Also depends on some fairly finicky carpentry/cabinetry techniques. But here's a great chance to learn.

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Final thought - you can always choose to allocate time and effort to something else and just replace the chairs. It's an unpleasant option, but is a time-saving.

Answer 7

All great answers, but if the same problem re-occurs, the next step is to use metal straps, that have a hole in their centre, for the bolt/screw, and a couple of smaller holes in the ends, to drive screws through into the two sides.(As in the strap will have a 135 degree bend at each end.) Yes, that could be a lot of metal straps and drilling, but in addition to the other solutions, will make it a job that only needs to be done once.

Answer 8

In addition to fixing any holes that are stripped, if you got a nut and washer on the other side of the diagonal block, you could tighten it to the diagonal block and that should help prevent that particular failure mode. I think in order to accomplish this, you would have to remove the block first by taking out the 4 smaller screws, put the inside nut/washer on the main screws and then reinstall the block. I'm not sure it's actually feasible but let me know if you need clarification.

Answer 9

I am sorry to say that I think I don't like that construction. The crosspieces should have a mortise and tenon joint into the leg, in addition to being glued as you say. Maybe they do; I can't tell from the pictures.

The bolts should go into a metal threaded nut inserted into the leg. Ideally there should be one in the crosspiece as well. Without that they will eventually work loose from the wood and back out from the hole in the leg without rotation as your lower picture shows, even if the bolts are held in place to the crosspiece as suggested in other answers. If you can install inserts into the legs your chairs will give you fewer problems. That will be hard with the crosspiece in place and it should have been done when the chairs were made.

I have a table made this way with a single large bolt through the diagonal crosspiece into the leg. It is held there by a wingnut. It's easy to remove the legs for transportation (the top comes apart, too, in a puzzle-like way) and re-assemble the table. I've had that table for several decades and moved it half-a-dozen times.