# Chair leg repair advice



## Kidneycutter (29 Jan 2021)

Need to repair a chair. The leg has broken at the castor - the is still intact. WD thinking of cutting the shoulder flush and dowelling a new block on.


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## TheUnicorn (29 Jan 2021)

not following the details. what is still intact? armchair / dining chair? maybe pictures if you can


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## Kidneycutter (29 Jan 2021)

TheUnicorn said:


> not following the details. what is still intact? armchair / dining chair? maybe pictures if you can


Ok sorry, should have proof read before posting. It's an arm chair with square shaped castors and the lag has broken right below the shoulder of the castor seat.
Will post a picture soon


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## TheUnicorn (29 Jan 2021)

much more sense with the pictures, from what I can see the solution (or at least the first thing to try) would be as you suggested, clean cut at the bottom of the leg, block of wood in the castor housing, attach the two, I would opt for a domino rather than a dowel (or maybe use two dowels if space permits?) as that would give it a bit more support against twisting. I'd also suggest that you make sure the castors are all flowing freely as if you sit in the seat and it tries to roll but the castor binds that would stress the repair


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## Inspector (29 Jan 2021)

Doweling or Dominoes to hold a little square stub is not going to work. Better would be to take a square and taper the top into a long point. Like a file or chisel tang and cut a matching socket for it in the leg. Glue that in and it should hold as good as anything else. 

An easier way is to cut 5" or 6"diagonally from the bottom to the opposite side and glue on a new piece of wood so you can shape the bottom to match the castor. Problem with that method is matching the wood/grain and having to refinish the leg, if not the entire chair.

Pete


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## Jacob (29 Jan 2021)

I don't think adding a block would do, however you fixed it. It'd break again with too much leverage from the off-centre castor.
Simplest would be to trim off all four castors and go castor-less in a slightly lower chair.
Strongest (with castors) would be to splice on a good length - 10" perhaps? and reform the leg. Long shallow angle splice for a good glue area.
PS I see Pete is saying similar - beat me to it!


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## TheUnicorn (29 Jan 2021)

Inspector said:


> An easier way is to cut 5" or 6"diagonally from the bottom to the opposite side and glue on a new piece of wood so you can shape the bottom to match the castor. Problem with that method is matching the wood/grain and having to refinish the leg, if not the entire chair.


 is the point of the diagonal cut just to give more surface area for the glue?

I would have though a half lap would give more support


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## Jacob (29 Jan 2021)

TheUnicorn said:


> is the point of the diagonal cut just to give more surface area for the glue?



Yes, sort of. A better structural joint.



TheUnicorn said:


> I would have though a half lap would give more support



Two glued end-grain joints to open up with eccentric loads. I reckon a straight splice (long) would be stronger.


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## Kidneycutter (29 Jan 2021)

Thanks for the replies. My other thought was to turn a block on the lathe so the dowel was part of the block or would this create a weak point?


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## Inspector (29 Jan 2021)

Yes the diagonal cut is for more glue surface. The lap has two end grain ends that add no strength and the face grain glue area is smaller than the longer splice. Modern glue will make the splice as strong as the original wood. Hint make the piece you are glueing on a little bigger than the leg so if it shifts a bit while glueing you can shape and trim to size after.

This time Jacob is quicker than me but saying the same.

Pete


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## TheUnicorn (29 Jan 2021)

so with the long splice its all glue, no dowels or similar?


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## Jacob (29 Jan 2021)

TheUnicorn said:


> so with the long splice its all glue, no dowels or similar?


Yes. Dowels make weak points.


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## Inspector (29 Jan 2021)

Kidneycutter said:


> Thanks for the replies. My other thought was to turn a block on the lathe so the dowel was part of the block or would this create a weak point?



It is better than a dowel in a little block but not as good as as the long glued splice. Problem with it is too big a dowel for the bottom square strength makes for thin leg wood around the dowel. Make the dowel small enough for leg strength and the square bit in the castor is weak once more. 

Pete


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## Inspector (29 Jan 2021)

Modern glues make the scarf joint as strong or stronger than the wood. The other option is to keep large people off the chair.

Pete


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## TheUnicorn (29 Jan 2021)

Jacob said:


> Yes. Dowels make weak points.


I'm obviously wrong, but I would have said that with a diagonal cut, all of the weight in the seat would just drive the joint apart, with the lap joint the weight in the seat is pushing wood together. I'm genuinely suprised that glue is strong enough for the strain. I'm assuming were talking just a quality pva based woodlue, titebond 2 or whatever?


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## Kidneycutter (29 Jan 2021)

I'm going to resin this - west system.


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## Jacob (29 Jan 2021)

TheUnicorn said:


> I'm obviously wrong, but I would have said that with a diagonal cut, all of the weight in the seat would just drive the joint apart, with the lap joint the weight in the seat is pushing wood together. I'm genuinely suprised that glue is strong enough for the strain. I'm assuming were talking just a quality pva based woodlue, titebond 2 or whatever?


Have to be a well made joint - long for good glue area, close fitting dead flat surfaces slightly roughened with light pass of sandpaper, glue spread thick on BOTH surfaces, clamped nicely - and end to end to stop them sliding apart. The stuck in part to be well over size and planed down to match existing.


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## sammy.se (29 Jan 2021)

how about making the chair a bit shorter all around? tapering the broken leg into the castor


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## Tuna808 (29 Jan 2021)

Scarf joint as suggest is the one I would go with,glue and weight issue isn’t a problem as the weight is distributed.I use scraf joints for guitar necks and the take a huge amount of stain from the strings.
straight scarf or the following.


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## cowtown_eric (30 Jan 2021)

Having had to repair a few chair legs over the years, doweling is to me a fools errand, as even a slight misalignment of dowels, as often happens as the brad point drill follows the grain, yields either an incorrect fit on the surfaces to be glued, or an imperfect match of outside surfaces, which could be sanded and then you'd go down the rabbit hole of matching finishes

So, albiet anatheme to the "restoration" bibles, as often the break is in an are of angular grain, I took to boring a very slightlyoversized hole and inserting a metal rod slathered with epoxy, carpenters glue on the flat break areas, clamp and align- or vise-versa

Anyway, that's what i do

Eric


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## TheUnicorn (30 Jan 2021)

cowtown_eric said:


> Having had to repair a few chair legs over the years, doweling is to me a fools errand, as even a slight misalignment of dowels, as often happens as the brad point drill follows the grain, yields either an incorrect fit on the surfaces to be glued, or an imperfect match of outside surfaces, which could be sanded and then you'd go down the rabbit hole of matching finishes
> 
> So, albiet anatheme to the "restoration" bibles, as often the break is in an are of angular grain, I took to boring a very slightlyoversized hole and inserting a metal rod slathered with epoxy, carpenters glue on the flat break areas, clamp and align- or vise-versa
> 
> ...


so the metal rod sits loose it the epoxy? acting like a dowel?


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## SaltyBob (30 Jan 2021)

If your wood is sound, I would follow the earlier post and Use West System epoxy; In the past 8 years I have built several rowing boats, clinker(marine ply & 1/4" laps) which (before Covid) were on the sea every week with crews of 5 and are have never sprung. The heavier sections (keels, gunwales, ribs) use 8:1 scarfs, but the planks are just lapped. The West System epoxy is considerably stronger than any timber, even just butted. Use only when temp is >5 degrees C, 'wet' both surfaces (and dowel, if used), mix remainder to peanut butter consistency with colloidal silica or micro fibers, this will 'pack' the joint (or equivalent); clean wet work as well as you possibly can, leave 24hrs then sand; 'simples'. (Your should be able to buy a 'small 300g pack' for about £18.00; expensive, but if kept out of the frost, will last for years)

Dont know about Araldite?

Bob


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## TheTiddles (30 Jan 2021)

Why is that chair on castors? I’m surprised that’s the only bit that’s broken, it looks very susceptible and castors will put dynamic loads that it may well struggle with. I’d go for cutting them all off and if it’s too low, adding feet back on tennons.
Aidan


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## peter-harrison (31 Jan 2021)

cowtown_eric said:


> Having had to repair a few chair legs over the years, doweling is to me a fools errand, as even a slight misalignment of dowels, as often happens as the brad point drill follows the grain, yields either an incorrect fit on the surfaces to be glued, or an imperfect match of outside surfaces, which could be sanded and then you'd go down the rabbit hole of matching finishes
> 
> So, albiet anatheme to the "restoration" bibles, as often the break is in an are of angular grain, I took to boring a very slightlyoversized hole and inserting a metal rod slathered with epoxy, carpenters glue on the flat break areas, clamp and align- or vise-versa
> 
> ...


Me too


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