repairs to M and T joints on chairs

[neilyweely]

Hi Folks
I have committed myself to fixing about a hundred chairs, in a restaurant, that are all developing the same problem. The mortice and tenon joints are becoming loose and are allowing movement in the chair, for instance when people lean back etc.....
I need an economical way to remedy this problem, production line style, but in the restaurant premises, preferably without taking the chairs to pieces. I did think about injecting a glue into the joint then using the kreg (one of) or the like, however the M+T joints are already reinforced on one side with a pocket hole screw so this may prove difficult. I believe there is enought room to get another screw in without causing damage, and with some success, but just wondered if there were other ideas?
Funny thing is that the chairs are quite nice looking; leather seats and backs, fairly decent materials and quite new-ish. There are angled struts running across the inside of the 90' angles (inside the mortice and tenons) to strengthen them, so that is a dead duck.

My problem is time. I need to get it done sharpish. If possible. Family comittments will doubtless call me away before long, so.....
I have done this sort of thing before, but never so many and never where I needed to get them done quickly and still as well as possible.
Help???

Thanks folks
Neil

 

[OPJ]

What about using Miller Dowels?

Clamp it up, take the screw out, drill the hole, drive the dowel in with a fast-setting PVA and you're done (once you've trimmed it flush).

I can't think of a better solution without having to take the joints. :S

If the tenons are in tact you could look at driving smaller dowels in from the sides, so the joints cannot slide apart.

 

[neilyweely]

Hey Olly

I do have a miller dowel set, trouble is I only have the small ones. That said, they may be the only ones that are suitable.

You are right though, that is a good idea. I was worried about using a screw from the outside as it would ruin the 'look' of the chair and be visible. But a flush cut miller dowel? Well, that might look OK. And fitted correctly would stop any 'pull' on the joint. Problem is though the gaffer may not like the idea. I think he was after an invisible fix, and I am not sure i could get inside the chair enough to fit a dowel throught the tenon to firm it up and stop any movement. I'll have a look, it is certainly a better idea than screws, eh? Cheers Olly.

Has anyone done this??

Thanks again

Neil

 

[woodbloke]

Hi Folks
I have committed myself to fixing about a hundred chairs, in a restaurant, that are all developing the same problem. The mortice and tenon joints are becoming loose and are allowing movement in the chair, for instance when people lean back etc.....
I need an economical way to remedy this problem, production line style, but in the restaurant premises, preferably without taking the chairs to pieces. I did think about injecting a glue into the joint then using the kreg (one of) or the like, however the M+T joints are already reinforced on one side with a pocket hole screw so this may prove difficult. I believe there is enought room to get another screw in without causing damage, and with some success, but just wondered if there were other ideas?
Funny thing is that the chairs are quite nice looking; leather seats and backs, fairly decent materials and quite new-ish. There are angled struts running across the inside of the 90' angles (inside the mortise and tenons) to strengthen them, so that is a dead duck.

My problem is time. I need to get it done sharpish. If possible. Family comittments will doubtless call me away before long, so.....
I have done this sort of thing before, but never so many and never where I needed to get them done quickly and still as well as possible.
Help???

Thanks folks
Neil

The perennial problem with chairs. If they look newish and have an angled support piece inside the internal 90deg, my guess is that they won't have been m/t at all but will be dowel construction, which is a favourite way for chair construction and probably why they're failing so soon 'specially with unejumercated customers who probably don't know how to sit properly on a chair.
Doing this sort of job quickly and 'on site' is not something I'd come anywhere close to even attempting as to do a half-decent job would entail stripping the joints down, cleaning up and then re-gluing. I'd also then dispose of the angled metal(?) bracket in each corner and fit a big triangular block of timber (again, the traditional way to reinforce the corner) which is glued and screwed with some big 'uns :wink:
Olly's suggestion is a sound one but I think is only a temporary 'quick fix' - Rob

 

[OldWood]

Having worked for a period with my cabinet maker brother and had to do something similar, I now look on chair design with a pretty sceptical eye.

For any chair that is going to have to work hard, it must be adequately braced in the lower frame. All to often chairs are just not designed to be mechanically effective, and there is absolutely no way that a purse can be made of a sow's ear - there must be stretchers between the front and back frames. If these 100 chairs are inadequately designed / built then you are onto a hiding for nothing and really the best option is to find a way out of the task.

Having said that I have just repaired 5 second hand chairs for my son with Chair Doctor glue. I will be interested to see how long this seemingly effective tightening of the joints will last. The material would seem to be a watered down PVA of some sort - that is it is white, thin, water soluble and not expensive. A £7 kit from Axi will go quite a long way - not a 100 chairs but 2 or 3 kits would do and would be a quick and on site repair. I would be tempted to go that way and if the repair doesn't last wash your hands on the basis of lousy cheap chairs!!

Rob

 

[neilyweely]

my guess is that they won't have been m/t at all but will be dowel construction,

err - Definitely mortice and tenon. Not sure if I said they were metal angle supports, but they are wooden, not triangles but with 45' ends so they fit in the corners nicely with ends flush to the sides. Then a screw driven in a la Kreg to keep the strut in place (sort of like a bit of timber herringbone in floor joists, if you know what I mean?)

Bearing in mind they ARE M + T's I did wonder if there was any use in setting a couple of dowels through the tenon, over and under style, in order to stop it from moving. What I would ideally like to do is slightly offset the dowel holes through the mortice and tenons so the dowels would pull the m+t together. This may be impossible as I don't want to take the chairs to pieces if I can help it. But even without the offset.....

Oldwood - I agree, I have seen (and made) too many chairs which have been sub standard design wise for heavy use. Certainly restaurant chairs need to be of a very high standard robustness wise in order to put up with all the lager louts etc (indian) rolling about on said chairs.

As I said, these really do not look too bad, I bet they cost him a pretty penny, and obviously not all 100 have come unstuck - yet, but the man has a plan and this is to fix the loose ones and make sure the others don't go the same way. Enter me.
I think I can probably do some good with my (?) idea of over and under dowels through the tenon, coupled with some glue (I have seen chair doctor, never used it; will it be better than PVA?) and will give this a go on a 'prototype'.

I did wonder if there was a product that you could inject into the wood that would swell up the timber in a localised area, thus compressing (in effect) and tightening the joints? (like a biscuit swells?) Not sure if I have heard of it or if I have just invented something amazing!!

Oh well, junior is asleep again, so I can float some ZZzzZZzz's again. Have you seen the time?

Thanks for your help Rob, Oldwood, much appreciated.

Neil (bug eyed and tired)

 

[Steve Maskery]

All good advice so far.

I wouldn't touch it with a barge pole. Get him to commission 100 new chairs!
S

 

[JWF]

Neil

What you describe in the latter part of your last posting is what "Chair Doctor" does. Drill a small hole, the size of the hypodermic needle, into the space in the mortice and inject Chair Doctor. It swells the tenon into the mortice and glues it as well. As far as I aware it is not watered down PVA.

Hope this helps

John

 

[OldWood]

Neil

As far as I aware it is not watered down PVA.

John

Yes, I will admit to that being an assumption, but the 'PVA' family is pretty big nowadays and has a range of capabilities. What lead me to suggesting it is a PVA type is the colour, the water solubility, the setting time, the smell ... do you want me to go on ? I don't think that that denigrates from the product one iota - but Chair Doctor is quick and easy to apply, it does seem to be effective and it is not expensive.

Rob

 

[neilyweely]

Ok, how about this. I will explain that there is a possibility that all efforts will be futile, and that in my opinion he is better off buying new chairs (although the problem is that only a percentage of them are failing so far). I know this guy, and he is not gonna want to do that; he will want me to have a go.

At least I have told him. Then I can proceed with the chair doctor idea, and perhaps drill and double dowel the tenons at the same time.
I did fix up a dozen garden variety chairs, and used the kreg jig which so far (a year later) is still doing the job. That said it was at an old folks home, so I don't suppose they get the same battering as those in an indian restaurant!!!

Steve - Thanks mate.

JWF - I am in Bedford, if you ever want to meet up for a yarn PM me and I'll send you my number. Am in Town Centre-ish.

And Rob - If it has four legs, stands in a field, moos and leaks milk, then its a cow, eh?

Cheers folks

Neil

 

[woodsworth]

without seeing the chairs it is hard to say if such a repair would work. I would suggest doing a test group of chairs. Do the chair doctor idea and see how well they last after the fact. No sense doing a hundred if they are all going to fail, especially if you know him.

Tell him it is a gamble and he may get some time out of them which will prolong getting new ones which is the idea.

That being said all it takes is for someone who is terribly over weight to sit on it and lean back land on the floor! That wouldn't be good for business in my opinion.

I have repaired chairs in the past but they are usually antique ones of some value. They are usually hide glue as well which is easier to repair, that is as long as no one has done another repair using some other glue that needs to be cleaned out.

good luck

 

[Matt@]

possibly a bit late to this thread but as a pro restorer, I wouldnt touch this job with a bargepole. Chairs in commercial enviroments get a hammering and you cannot in any way warrant any of the regluing you'll do and the likelyhood is that whatever you do, some/all will work loose over time. Heard reports that chair doctor loses effectiveness over 12 months as the expanded joint shrinks back. Dowels through the side of tenons will always work loose in time but by definition won't fall apart so thats a blessing! Get out of the job altogther - its a nightmare IMO

PS How much would you be charging for these out of interest? is it a paying job or a favour??

 

[Jake]

Nail down some exclusion of liability/indemnity provisions in case chairs fall apart under customers, whack in some coverhead screws through the tenons and run away with the loot.