Thread: tightening up the back/seat joint of some chairs

Pictures please.

If the joints are loose enough to get a saw blade into (oscillating saw if you're lucky) taking one chair apart might be an option.

questions at this stage are
what tools do you currently have for the task?
how confident are you with your hand tool skills?
how competent are you using the power tools you already own?

how much are you prepared to invest in repairing these chairs?

Originally Posted by ian

Pictures please.

Here are the requested pictures.

These are from the Broyhill Brasila line and I believe they are made of walnut. As mid-century modern antiques, they go for $100-$250 each. I looked this up because I probably wouldn't try this unless I could replace one if necessary.

chair_front.jpg

The joint that is loose is the joint between the back/leg and the seat. You can see that the back/leg is a single, rather slender single piece of curved wood.

chair_profile.jpg

This is a closeup of the joint where it is coming apart. You can see the dowels in this picture. Not every joint is as open as this one.

dowell_joint.jpg

Originally Posted by ian

If the joints are loose enough to get a saw blade into (oscillating saw if you're lucky) taking one chair apart might be an option.

Some of the joints are open enough to get an oscillating saw blade into, but I'm not sure that all of them are. It seems that since the joint is loose, I should be able to pry it open. How would the joint be loose if the glue is still holding. Is that correct, or am I wrong?

Originally Posted by ian

questions at this stage are
what tools do you currently have for the task?

I have a pretty complete shop, much of which I would not expect to use in this project (table saw, SCMS, etc). I have an oscillating saw, a bench top delta drill press, a bench top delta band saw, a bench top belt sander, a router, a small router table, and most hand tools you would expect. If it was really necessary to have something special, I could go and use a local collaborative workshop that has pretty much everything and is reasonable to use per day.

Originally Posted by ian

how confident are you with your hand tool skills?
how competent are you using the power tools you already own?

I am an okay carpenter. I built the desk I am sitting at as well as most of the built-in bookshelves in my office. I have done a fair amount of furniture refinishing. I have installed custom windows in a stone foundation, repaired broken floor joists, installed new wooden floors, refinished wooden floors and woodwork, re-built a porch with new windows and interior wood trim and wainscoat, and many other things that come with living in a 140 year old house. I generally think I can do most any project, but it will take more time and I will likely waste materials and such compared to an experienced carpenter or joiner. There issue here is that there really aren't materials to start over with if things go south like there would be if I was making something new. I am prepared to take some risk in that direction in that I will be careful and can replace a chair or so if I really mess things up.

Originally Posted by ian

how much are you prepared to invest in repairing these chairs?

That's a difficult question to answer. I was going to look into what it would cost to have them restored but I haven't got that far since I was going to try myself. There is a carpenters union trade school not far from here and I thought about checking with them to see if this is something they do there. I don't mind buying a tool or so and I don't mind about my time.

What costs would you anticipate with a project like this?

LMHmedchem

When we get repair jobs like this at work, the first option is always trying to non-destructively dismantle the broken joints - sharp taps with a mallet to the leg as close to the rail as possible. If you can pull it apart without breaking anything, it's generally ok to just sand/chisel off the dried glue and re-assemble with new glue. You can also glue and screw corner blocks between the side and back rails if there aren't already some.

The angle between the side rail and the back leg will probably make it a bit trickier to get your holes lined up for new dowels.

If you want to pay someone, probably allow for 1.5-2 hours at whatever the going rate is there; we charge $80/hr

Picking up on Elan's comment re glue blocks.
Do the chairs already have glue blocks under the seat? Can you post a photo of the underside of the seat?

Originally Posted by elanjacobs

The angle between the side rail and the back leg will probably make it a bit trickier to get your holes lined up for new dowels.

If I was doing this with a piece of steel on a milling machine I would use a pointed centering bit to center the existing hole under the bit, clamp down the piece, and change out to the next higher size bit. That would center the new, larger hole on the existing hole. I would finish with a reamer bit to get the hole perfectly round. It seems like this would work here as well, but I would have to get the existing dowel out of the hole and I'm not sure how I would do that.

Just cleaning up the old glue with some sanding would be ok, but I really don't like to re-do this kind of think. I would rather take more time and have a repair that would outlast me. The next time can be someone else's problem. I also like simple solutions though, so I am still a ways from a decision.

If I can't get the joint apart be tapping what other method can I use. I think you can see from the pictures that these are not very robust chairs so there is only so much that I can lean on them. I don't mind using the oscillating say, but that would preclude re-using the dowels and might make it much harder to get the old dowels out.

LMHmedchem

I have pulled joints apart by sawing thru the dowels with one of the thin japanese blades that have no set.

Originally Posted by ian

Picking up on Elan's comment re glue blocks.
Do the chairs already have glue blocks under the seat? Can you post a photo of the underside of the seat?

There are corner brackets under the seat but I don't know if they are glued. There are 4 screws in each corner (two to the side rail and two to the back rail). There is also a screw in each corner where the seat is attached. I think you can see the screw holes well enough in this picture. Let me know if not.

seat_underside.jpg

The screws look like brass flat-head screws and I certainly could replace those with a bit bigger size. To my eye, the angle of the brackets doesn't look like they can really do much to keep the back in place. It looks like they are anchored too close to the center of the back rail to hold the back very well.

Originally Posted by Bohdan

I have pulled joints apart by sawing thru the dowels with one of the thin japanese blades that have no set.

How did you get the old dowels out after you cut the joint apart?

LMHmedchem

I somehow managed to post my message twice.

LMHmedchem

I agree with Elan. A packer to protect the timber and a few good love taps will open it.

If not, or its open a bit, do as Bohdan suggests, use a japanese saw to saw through the dowel.

You'll need to take off the under seat brace, which may or may not be glued. Ive found it usually isnt.

For the dowels, drill out the old ones with a larger forstner bit, glue in a new dowel to fit. Once dry, fit new tenons.

LDH.
You sound like you have a reasonable grasp of woodwork and the various tools.
As suggested, carefully dismantle the thing , clean up and re-glue.
If you have trouble getting the joints fully apart, cut the dowels leaving a little bit of each dowel a bit proud of the leg or seat. Using your doweling jig, slip it over the old dowel and drill it out with the same size drill bit. Glue new ones in.
I think you will handle this easily.

John

Originally Posted by LMHmedchem

There are corner brackets under the seat but I don't know if they are glued. There are 4 screws in each corner (two to the side rail and two to the back rail). There is also a screw in each corner where the seat is attached. I think you can see the screw holes well enough in this picture. Let me know if not.

seat_underside.jpg

The screws look like brass flat-head screws and I certainly could replace those with a bit bigger size. To my eye, the angle of the brackets doesn't look like they can really do much to keep the back in place. It looks like they are anchored too close to the center of the back rail to hold the back very well.

to get some of the engineering out of the way...

The corner blocks provide a place to attach the seat and also stiffen the chair to resist diagonal racking.
if the blocks were cut properly, they should be a good fit to the seat rails and normally would be attached with glue as well as screws. The close fit between the braces and the side and rear rails strongly implies a glued joint.

the front and back seat rails are probably doweled into the front and rear legs with two dowels per joint. I think it unlikely that the front rail is attached to the front legs with a mortice and tenon joint.

The side and rear rails appear to be of laminated construction -- which strongly again implies dowel joints.
There will be very little meat left where the dowel joints cross inside each leg. Perhaps less than 1/8".

If the braces don't easily pop off after you remove the screws, you will have to cut them away from the seat rails. Try and make an accurate pattern before cutting them off as that will make making replacements easier. To avoid damaging the rails, I'd probably use a straight saw cut a short distance away from the rails. A furniture maker's rasp and sanding is possibly the cleanest way to remove the residual bits of each brace after sawing.

Lastly, I'd only work on those chairs where the joints that are loose enough to be visible. These are likely the chairs used most often by heavier people -- other chairs in the set are possibly in good enough condition to leave for another 10 to 20 years before restoration.

I started with the first chair today. I picked the chair the loosest chair I could find and removed the seat. I then removed the screws from the corner braces. I did some tapping on alternating sides to separate the back and seat. It came apart fairly easily but a piece of one of the legs broke off when the joint came apart.

broken_rail.jpg

The break is fairly clean and I think that if I clamp it tightly I can glue the splinter back without it showing much.

This makes me very hesitant to continue with other chairs unless there is a better way to get the joints apart. Posters in the glue forum mentioned using hot water or a heat gun to loosen the old glue. Is that something that can be helpful or more likely to do harm then help? One of the dowels broke in half and a piece of wood from the leg near the dowel holes pulled off so I suspect that what happened is that some newer glue in the joint was still holding even though the original glue was not.

Is there any advice regarding how to glue the broken piece back in place so that it will look as good as possible?

LMHmedchem

Firstly, I would have used a japanese saw to separate this. They have zero set and make a fantastically clean and small cut. To ensure you get no marks, put painters tape either side to act as a slide/protectant for the surface.

With these breaks, I use the same painters tape trick. I don't clamp. When glueing, put painters tape over the break and cut it with a scalpel (or sharp knife) right to the edge. This is so when you get glue squeeze out it doesn't ooze out everywhere. It can be wiped up easily.

Secondly, with chairs and fancy curves, to save making elaborate clamping jigs, I use massive elastic bands rather than clamps. You can get giant ones from Officeworks. They are 20mm wide. Cut them and wind them on like a bandage. The pressure they apply is fantastic.

Lastly, to clean up the glueline without damaging the finish, I use the blade-and-tape-trick: https://www.youtube.com/watch?v=rTVScFJoe24 (skip to the one minute mark).

Originally Posted by woodPixel

Firstly, I would have used a japanese saw to separate this. They have zero set and make a fantastically clean and small cut. To ensure you get no marks, put painters tape either side to act as a slide/protectant for the surface.

I don't mind using a saw to remove the joints but then I will not be able to re-use the dowels. That makes this a more significant project where I have to remove and replace the old dowels instead of just cleaning them up and re-gluing. I am still not sure how I would go about getting the old dowels out and about how to re-drill the holes.

If I leave a small amount of each dowel as has been suggested, will there be enough there to fit a dowel jig down over the remaining piece of dowel and then drill? It seems as if that might be a good way to remove the old dowels and create new holes that are lined up.

Originally Posted by woodPixel

With these breaks, I use the same painters tape trick. I don't clamp. When glueing, put painters tape over the break and cut it with a scalpel (or sharp knife) right to the edge. This is so when you get glue squeeze out it doesn't ooze out everywhere. It can be wiped up easily.

I don't see how I can get this tight enough without clamping or using the rubber bands as you suggest later. The broken fragment doesn't seem to sit perfectly flat and I need to apply some pressure to get the crack to tighten up. I will clean up the area around the dowels some and that may help. I will only get one shot at re-gluing this fragment, so it will need to be held in place as tightly as possible to minimize the appearance of the crack.

Originally Posted by woodPixel

Secondly, with chairs and fancy curves, to save making elaborate clamping jigs, I use massive elastic bands rather than clamps. You can get giant ones from Officeworks. They are 20mm wide. Cut them and wind them on like a bandage. The pressure they apply is fantastic.

I will get some of these tomorrow.

Originally Posted by woodPixel

Lastly, to clean up the glueline without damaging the finish, I use the blade-and-tape-trick: https://www.youtube.com/watch?v=rTVScFJoe24 (skip to the one minute mark).

I will check this out, thanks.

Should I use hide glue to repair the fragment that has broken off or should I use regular wood glue for that?

I don't have a doweling jig at the moment. I don't mind getting one but there are allot of options. I don't mind spending something for this but the main thing is that it is easy to use, specifically for this situation.

Here are some options I found,

Milescraft 13090003 DowelJigKit with Milescraft JointMate ($20)
DCT Woodworking Self-Centering Dowel Drilling Jig & Bushings Set ($25)
Milescraft 13110003 Joint Pro Doweling Jig ($54)
Dowl It 2500 Dowel Self Centering Jig ($55)

Can anyone make a recommendation? If I understand how the Milescraft 13110003 works, you can fit and drill both the boards you are joining at the same time which would be helpful. I am really just guessing though. There is quite a range in price and I don't see any difference between the $25 DTC jig and the $55 Dowl It jig.

LMHmedchem