Oak kitchen chair - all wood and seat is built by gluing three or so boards on edge.
Repair issue is boards are starting to work loose and need reglued.
So the question is how do professional wood repair shops handle this problem?
As stated the entire chair is wood, rungs in seat and seat back (vertical) are glued, seems that the chair would almost have to be separated to rebuild to drill, add dowels, and reglue. That has some risk in damaging the rungs and such that are still tightly glued.
How is this repair accomplished? I see it difficult without separating the entire chair to enable drilling, inserting dowels, and gluing, to make a bottom seat repair. Separating the strong joints will carry a lot of risk, there is a constraint here.
Doyle
Dowels do not add any structural strength. A good edge-grain glue job is stronger than the wood. The dowels do help with alignment (assuming you do it exactly spot on).
Would it be possible to add some reinforcement from the bottom -- pocket screws or dutchmen?
If there is any gap in the joint, you can get some glue in from one side and suck it through with a vacuum from the other. But glue on glue is not the strongest joint.
You will have to clean the joint out the best you can. Removing all old glue nut no wood. A thin knife is best for this. Sting, anything to break away the old glue and debris in the joint. Clamp it dry to be sure it will all come together perfectly and if it doesn't then clean it out again. When it meets perfectly loosen the clamps and add some glue. clamp to the point where it starts to ooze and let it set. You can add like a 1/4" plywood to the underside rasp the edges at a long angle to make it less noticeable. But you will need to get a good glue up first.
Thanks for the response - You two:
Keith - that is an interesting response - regarding the dowel not adding strength. Makes sense as it is all wood even after drilling and inserting a dowel. Probably stronger without the dowel. But, I suppose a tongue and groove joint would enhance strength as there would be more surface area than the butt join to apply glue to. Like I said - interesting, never thought of the vacuum technique.
Paul: Got you loud and clear on cleaning and butt gluing with added bottom support - glued I assume. Hard to see but it doesn't appear that there is much residual glue - which I don't understand why a factory wouldn't have added but such small amount.
To Add: Your two recommendations is the way I was going to go intuitively, but the idea of adding dowels drew me into thinking that it would be stronger (forcing strong joints apart to repair was tough to fathom). But, I understand - no, wood dowels will not add strength. Essentially clean with care and it should be repairable with good glue.
BTW, I use Carpenters professional wood glue and clamp. In this case, it appears I will be able to spread the joint about a 1/16 inch to help applying the glue.
Good advice!!
Doyle
The best repair is to disassemble the chair rather then pocket screws, drizzling glue into slightly open joints or drilling dowels through the furthest ends into the center of the chair seat. To aid disassembly vinegar may help but sometimes you just need to tap apart with a rubber mallet or force apart by twisting and pulling on a joint that is already compromised.
Once apart - scrape edges and lightly sand - don't round over edges..... - dowels or biscuits can add tremendous strength however not necessary with a long grain joint. Use yellow glue - clamp overnight and leave the rungs and crest rail for another day. As long as you're at it - I'd do the legs as well - Always dry fit and plan your glue up before applying the glue.
SA
The project amounted to several chair bottom repairs. I took the advice of all that responded and came up with two or three estimates of cost depending on the method used. This information was provided customer who decided to go with the technique that called for adding a high grade plywood (hardwood veneer) added on the bottom side with the glue suggested here.
The customer agreed that total disassembly, cleaning, and gluing sounded very professional but didn't like the idea of spending more money on a process that appeared to be more risk (the separating of joints already tight).
I understood their position and did it the way stated. My time would have been significantly more in the other options presented.
The seat boards were brought to gether with clamps and looked seamless as possible and the chairs appeared very strong when completed.
That's how the situation worked out.
Thanks for all the ideas, it represented a great study of the issue at hand.
Doyle