# Advice on cleaning up dodgy mitre joints



## IanB (1 Aug 2021)

I'm having a go at making my first small box with mitred corners, but a couple of the corners slipped a little during the glue up. (I used masking tape on the joints but didn't seem to get a tight enough join, so added some clamps which I think is when the slippage took place).

So, is there a 'least worst' way to clean up the corners on the outside and remove the protruding edges and disguise it as best as possible? Plane, pare with a chisel, flush cut saw, sand, or something else? Or even plane a chamfer on all the corners?


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## TheTiddles (1 Aug 2021)

Inlay a square bead on all edges, mitred into every corner, easy to do with an accurate shooting board and will look very smart if you go for something contrasting like box or harewood


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## eribaMotters (1 Aug 2021)

As the mitre joint is not a strong one you may be able to break the joint open without damage, clean up and re-glue.
Option two would be to radius the corners with sandpaper around a block of wood,

Colin


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## recipio (1 Aug 2021)

Ditto. You will find that the joint comes apart with a few taps of a hammer. Its best not to use a PVA glue on mitres as they will slide and the glue actually has a definite but visible glue line. Use a mitre bond cyanoacrylate glue instead and reinforce with splines.


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## Ntre25 (1 Aug 2021)

If you don't want to take the joint apart and start again, the route of least resistance is to plane each side and reduce the thickness of all sides by the same amount. It is tricky as you need to avoid end grain break out on all the corners but it is possible with care and a really sharp smoothing plane


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## Derek Cohen (Perth Oz) (2 Aug 2021)

If a heat gun and water (=steam) does not open the joint, then use a Japanese saw (thin blade) to saw down the centre. (The saw is a good method to create parallel sides with mitre corners when the fourth corner is not a good fit).

You will never be happy with a poor fit or planing down the sides. Either do the above or toss in the bin as a learning experience.

What did you use to fit the corners together? For something like this, use tape on the corners, than a square form …
















Regards from Perth

Derek


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## IanB (2 Aug 2021)

Thanks everyone for all the helpful advice, I've learnt a lot! I think I may try taking it apart and re-cut the mitres for a slightly smaller size, especially as I seem also to have made the base a fraction too small and it's showing a gap along one side


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## thetyreman (2 Aug 2021)

I tend to avoid this joint unless it's reinforced with something like splines or cocktail sticks e.t.c which will help stop it coming apart when the wood moves.


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## TheTiddles (2 Aug 2021)

IanB said:


> Thanks everyone for all the helpful advice, I've learnt a lot! I think I may try taking it apart and re-cut the mitres for a slightly smaller size, especially as I seem also to have made the base a fraction too small and it's showing a gap along one side


Ok, definitely the best option then!


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## Derek Cohen (Perth Oz) (4 Aug 2021)

thetyreman said:


> I tend to avoid this joint unless it's reinforced with something like splines or cocktail sticks e.t.c which will help stop it coming apart when the wood moves.



Mitred corners in solid wood without using corner reinforcements? My recommendation is to first "size" the joint. This involves rubbing glue (e.g. Titebond ll) over the face of the mitre, allowing it to sink in and get close to touch dry. Before it is dry, add more glue to the faces and clamp the lot together. 

This should create a strong joint. The main reason why mitre joints are not strong enough is that the "straws" soak up the glue and the joint is glue-deprived. Block the straws by sizing, and the problem goes away.

Putting my money where my mouth is, I recently glued up a new plinth for a turntable. The wood is Jarrah ...






The corners are braced internally, but this has more to do with creating a rigid structure than a glue joint ...






Getting there …






When it comes to any corners not closing up perfectly, the easy way to fix these is by burnishing with glue and a smooth, round shaft.

Regards from Perth

Derek


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## thetyreman (4 Aug 2021)

Derek Cohen (Perth Oz) said:


> Mitred corners in solid wood without using corner reinforcements? My recommendation is to first "size" the joint. This involves rubbing glue (e.g. Titebond ll) over the face of the mitre, allowing it to sink in and get close to touch dry. Before it is dry, add more glue to the faces and clamp the lot together.
> 
> This should create a strong joint. The main reason why mitre joints are not strong enough is that the "straws" soak up the glue and the joint is glue-deprived. Block the straws by sizing, and the problem goes away.
> 
> ...



lovely job derek as usual!


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