Glue & chairs

ken lutes

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Winchester Ky.
I have project that involves taking a part and reglueing some old chairs. Would someone with experience on this recommend the best glue to use? Thanks ahead of time. Ken
 
High strength epoxy. It is one of the few glues we use that has good gap filling properties. The five minute stuff might also work, but the high strength stuff would be best. FWW or Wood (I'm pretty sure it is the former) magazine did an article quite some time back in which the author intentionally made all of his mortises a hair large and used epoxy to glue everything up. I, personally, would not go quite that far, but it does show the confidence one can have in the strength of epoxy.
 
My 'technique' involves removing the rungs, cutting a verticle slot in the ends, inserting a small wedge, slop on liberal amounts of your favorite wood working glue (I use Elmer's Probond), reinserting rung in leg and pounding in with a non-marring mallet to force the wedge to spread the rung for a tight grip. Then on the, less noticeable, inside of the leg, I drill a small hole to accept a round toothpick or 1/8" hardwood dowel and tap in with more wood glue. I actually prefer the toothpick because true hardwood dowels are pretty much a thing of the past. And, being small, they are easy to touch up with stain or paint to make invisible. Works for me.
 
What kind of chairs are you working on? I'm going to assume they are late 19th century or early 20th century factory made chairs. If so, the parts of the seat will be held together by dowels, two per joint, probably 3/8" or 7/16".

The first issue is to decide which joints need to be disassembled. For me, it's any joint that you can move the joined pieces relative to each other. Almost always, the back chair joint is loose, meaning that if you grab the back of the chair and push and pull it, the back moves relative to the seat (meaning that back joint is loose). Any joint that doesn't move should be left alone.

The next problem is to get the joint apart. Before you take the joints apart, TAKE PICTURES. You'll be amazed that you can forget how the chair goes together. Also mark the pieces - left, right, front, left leg, right leg. Left and right is as you are sitting in the chair. It also helps on the side rails to mark them "front joint" and "back joint" so you don't try to put them together backwards - don't ask why I recommend that.

You can pound on the pieces or use a clamp in reverse to push them apart, but doing so risks breaking the wood. If the joint is loose, I use a flush cut saw and cut the dowels always being careful not to cut the wood along the visible seam. If you're going to mark the wood with the saw, do it on the inside of the seat where it won't be seen when re-glued.

Use a drill one size smaller than the dowel and drill out the dowels. So if you have a 7/16" dowel, use a 3/8" drill. Use a small (1/8") chisel and remove the rest of the dowel along the side of the mortise. If you're careful, you can re-assemble with the same size dowel.

If you want to do a trial fitting, cut yourself some short dowels - maybe an inch - and do the trial fitting. You don't want to use full length dowels because they're hard to get out and you haven't put any glue on them yet.

For your real glue up, measure the holes carefully and cut your dowels a bit shorter. Remember that on the front legs, one dowel will likely interfer with the dowel from the other joint so allow for that space.

To glue up, use slow epoxy - not fast for a bunch of reasons - you want to have plenty of time to do everything and slow epoxy is stronger.

That's about it.

Mike
 
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A bit more. If you screw up in drilling out the dowels, or if someone else has tried to repair the joints and the holes are screwed up, you'll have to do some more elaborate repairs.

What I do is cut a 1/2" by 1/2" square loose tenon and make the mortises to fit. Transferring the location from one face to the other is not that difficult. Use a small combination square and mark off a line about even with the existing holes, using the visible face as a reference. Do this on both pieces (same distance on both pieces). Then on the rail, cut your mortises to fit the loose tenon. Now, run a line, using your small combination square along the sides of the mortises and bring the lines up the side of the rail. Put the rail against the other joint piece in the location you want it to be. Transfer the lines to the other joint piece. Remove the rail and bring the lines across the joint with your small combination square. Cut your mortises to those lines.

Do a trial fit before glue up - here you should use almost full length tenons to make sure the angle of the mortises are okay. You might have to trim a bit because you have two mortises and they both have to line up - makes it a bit more difficult, but only a bit. Once you have a good trial fit, measure the depth of each mortise and cut your loose tenons a bit short. Glue with slow epoxy glue.

[I guess that's more than you asked for. Sorry.]

Mike
 
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Oops, one more thing. You should make new corner blocks. Make them substantial and glue and screw them. Use slow epoxy here, also. Most of the old corner blocks are too small (too thin) to work well.

The only thing to watch for here is the height where the glue blocks are located if the seat sits on the glue blocks. You don't want them too high or the seat is too high. If too low, the seat will be down in the rails and it will be uncomfortable to sit on.

Mike
 
Would All Depend.... On the condition of the chairs and why they need reglueing.

For instance, just last night, my wife said to reglue the highchair befor Easter dinner. So Of course I obeyed and did. Problem was that the joints were loose, Not wiggle loose but simply glue failure, dried out, etc. I could pull each dowel and spindle out of socket, still a tight fit but no longer glued. I simply used Titebond and took all the spindles apart (remembering the order of distruction and laying them out, etc. Cleaned off the old clue and re-applied new fresh glue. Re assembled the chair and clamped it in place. This morning it was as tight and secure as ever and will outlast yet another grandchild. (oldest one is 17 and he started the chair, been 3 since)

In the past I have reglued some really old and wallered out joints, for these I have used Either Polyurethane glue or Epoxy. With these I usually work in small sections and repair segments that eventually fit together to make a complete repair.

I don't like to peg or brad the joints as this usually will not allow subsiquent failure or relief if the joint fails. It usually results in the peg or pin eating away at the tenon or allows the tenon to wiggle around inside the socket till it makes a giant hole and a rounded off peg. I feel that there has to be a way for the joint to fail should excessive force be applied, w/o breaking the parts down.

Often as not, If you get to the chair before excessive wear, It is not too important to re-invent the wheel and just re-do what was done before and get many more years of service.

Also there is a product on the market, Chair Doctor, I think, that you squirt into the loose joints and hold for 30 sec. I have used this with a good deal of success.

Also I have pried open joints and dripped in a thick CA re clamped and had great success.

Options are abound.
 
Just a comment. According to wikipedia, CA glue has low shear strength, and shear strength is what you need in a dowel joint (if it fails, the dowel will be pulled out of the joint). To quote the relevant section:

"Cyanoacrylate glue has a low shearing strength, which has also led to its use as a temporary adhesive in cases where the piece can easily be sheared off at a later time. Common examples include mounting a workpiece to a sacrificial glue block on a lathe and also tightening pins and bolts."

Mike
 
No matter what type of glue, OR which method you use, one of the most "IMPORTANT" items for a successful "Reglue", is to make sure that you get ALL of the Old Glue off of the tenons/dowels and out of the mortises/dowel holes and any other areas that had glue applied originally, so that the new glue can react with and attach to the wood, because the new glue WILL NOT attach well to many of the glues that have been used previously. (Slow setting Epoxy is the Best IMHO).
 
I'm surprised that nobody mentioned hide glue... lots of older chairs were made with it, and it is reversable... it dissolves in warm water, and if you add new hot hide glue, (unlike other glues) it will redisolve and stick to the old. It also has moderate gap filling capacity, unlike polyurethane glue (where the foam has no strength).

It was mentioned but not emphasized that carpenter's glue (PVA, titebond, etc.) only sticks to porous surfaces, not to dry glue or paint. I doubt if I could get things clean enough, so I would lean towards hide glue (if the original was the same, or epoxy.
 
I will remove as much of the old epoxy or glue from the joint as possible. After this I will check the joint. I f it is fairly tight, then re attach it with your favorite flavor adhesive:rolleyes: and clamp it. If the joint is lose and has slop, I will cut a triangle out of the bottom of te spindle and place a wedge in there. This will tighten up the lose joint and keep it for pulling out later.
 
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