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By Sgian Dubh
#1336419
Iroko is one of the world's least volatile movers as far as expansion and contraction in response to changes in moisture content, i.e., ~3.8% tangentially and ~2.8% radially throughout the 'Shrinkage Zone', that being from 30% - 0% MC of the wood. So that's a decent start.

However, even if your iroko top swings 2 percentage points either side of a fair median of ~10% MC over the typical annual seasonal response to changes in relative humidity found in habitable buildings, i.e., ~8% MC (winter) and ~ 12% MC (summer) in the UK you're likely to see shrinkage of up to 1.5 mm and expansion of a similar 1 to 1.5 mm, i.e., a total change in width of up to 3 mm, but more likely about 2.25 - 2.5 mm.

Given that, I wouldn't have framed your top as you've done because the mitres are highly likely to fail, or the two end cross pieces (mitred end clamps) might cause the top to split, all depending upon how well and solidly they're attached to the end of the panel. My suggestion is to remove that mitred framing if you can assuming that leaves enough length and width in the remaining top. If not, you'll just have to live with what you've got, and take on board the lesson about wood movement for the future.

I'd like to point you towards what I think might be a half decent source of information about woody topics ... but for the life of me I can't recall where I saw such a source, ha, ha. Slainte.
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By woodbloke66
#1336425
Sgian Dubh wrote:I'd like to point you towards what I think might be a half decent source of information about woody topics ... but for the life of me I can't recall where I saw such a source, ha, ha. Slainte.


I can't remember that source either but for all your woody information I'd thoroughly recommend 'Cut & Dried' by some bloke called Jones :lol: :lol: - Rob
By Mike Jordan
#1336432
You are right in saying that Iroko won't move as much as most other timbers, but it does still move enough to make the mitred edges an impossible task. No measurable movement occurs along the grain, but across the grain it cannot be restrained by any method. As the moisture content increases so does the width of the top. The mitres will gape as it expands or split off the side pieces as it contracts.
Those who use bread board ends learn to live with the fact that the ends are usually a different size to the width of the top. My suggestion is to rejoin the the top after ripping the boards used down to about 75mm wide, these are then arranged so that they alternate heart side up then down right across the width, that will prevent any distortion pulling the top out of shape and the ends won't need to be held straight.
The oily nature of the timber means that the only really suitable glue is two pack epoxy, other glues are prone to early failure. Please ignor the myths about degreasing the glue faces with solvents, it's nonsense.
I am hoping that you have fastened the top to the frame with buttons or expansion brackets to allow movement of the top to occur. If it's just fastened directly to the frame movement of the top could destroy that nice looking frame.
By Farm Labourer
#1336443
Mike - if you look really closely at the second pic, you'll see the buttons on the plastic in front of the legs!

Really appreciate everyone's input. I was trying to avoid any end grain showing - what other methods would acheive this aim?
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By woodbloke66
#1336454
Farm Labourer wrote:
Really appreciate everyone's input. I was trying to avoid any end grain showing - what other methods would acheive this aim?

The only other way to avoid seeing the end grain is to use so called 'bread board' ends. Personally, I would just opt for seeing the end grain and have done with it as there's nothing intrinsically wrong with that approach - Rob
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By MikeG.
#1336469
Farm Labourer wrote:...... I was trying to avoid any end grain showing


Why?

what other methods would acheive this aim?


Breadboard ends, as Rob says. Remember, they "float, being only fixed in the middle (there is a variation where they are fixed at the outside and the middle floats, but this requires gaps to be left between the boards of the table).
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By AndyT
#1336473
If you really want to hide all end grain, you could do what you did, but use veneered ply or MDF in the middle, not solid timber.