she oak and thermal distortion

[PAH1]

Made an interesting discovery the other day. I made a second box from some she oak I have, unfortunetly no more details than that. When I made the first box I fitted the lid and found that when it cooled the fit changed noticeably, I was not impressed but assumed that I had done something wrong.
The second box was made taking into account the lessons of the first ie the final fit on the lid was done when everything was cold. However the lid changes its fit from loose to tight, egg shaped to round simply by changing the room temp over a very short period of time. It is not humidity as that takes a far longer period but really temp.

I had not expected timber to be so thermally plastic over such short periods. Anybody else noted this sort of behaviour?

The piece of timber is probably river she oak, east coast, obtained from Dorrigo, it is also spalted.

[Skew ChiDAMN!!]

Definitely. I no longer make vacuum fit lids for exactly that reason. Some days the lids literally fall off, on others it's a case of don't even try... they won't budge.

I've also learnt not to leave items in jam chucks... they may be a perfect fit when turning, but it's so disheartening to head back to the shop and discover the item in pieces on the floor.

[Hickory]

Your She Oak (which is in the Pine family) is probably not a good choice for a lidded box. I am not versed on Aussie woods except to be in awe of their beauty, but local Pines move way too much with changing weather. Only way to approach such would be to use kiln dried woods only, that are taken to 6 percent MC. Allowed to acclimate to the shop (shed) area and then turn in one setting and apply as much finish as you can muster, both inside and out side the box. I would use a sealing hardening finish that can retard seasonal changes to maintain the fit.

Show a picture, I am interested in how the She Oak looks, compared to regional pines. I have seen She Oaks growing in Florida (here in the States) but never the wood.

[PAH1]

Your She Oak (which is in the Pine family) is probably not a good choice for a lidded box. I am not versed on Aussie woods except to be in awe of their beauty, but local Pines move way too much with changing weather.
Show a picture, I am interested in how the She Oak looks, compared to regional pines. I have seen She Oaks growing in Florida (here in the States) but never the wood.

The she oak family is very distantly related to the pines as it is a flowering plant. It looks like a pine because the leaves have been reduced to small brown scales in a whorl around the "leaf" which is actually a stem that has been adapted to photosynthesise. A lot of Australian plants do this, wattles (Acacia) are a good example.

I will try to get a picture of the box up, it is a very pretty wood. It is however one of the harder woods to dry well, Richard Raffan told me that one time he roughed out a large quantity of she oak bowls and when dried measured 12"x9" from long to short side.

Skew I have not had the problem with anything other than this she oak and then only in response to temp. Camphor laurel, walnut, fringed wattle, and a couple of others that I can't think of have not done the same thing.

[reeves]

yes. this behaviour happens cos Sheok, allocasurina fraserna and the torluosa (rose sheok) and inopholia (hairy oak) have the highest contraction along the grain of 'any' australian hardwood..about 12% max which is huge....hence its a bitch unless it is 'totally' cured...

this means that when its drying it will lose 12% of its usable wood area along the grain as opposed to across the grain..most other woods have much lower diverse contaction or r even with its self..

thats why they used to use it for shingles, splits well and is pretty hard...

even fully cured its more prone to weather changes than most...sun, humidity....eventually if it cant move it will fully stabilise and be quite good...

u may need to either make better structural reinforcements or take into account wood movement..

i find its best being 'very careful' with it in terms of keeping it in a cool place and being aware of its propensity to split and move...man cut some rose sheok recently from fallen logs and u can see it start to split up in minutes as soon as moisture is released...

still its grain is worth any pain in my book...

cheeeeeers

[Skew ChiDAMN!!]

Skew I have not had the problem with anything other than this she oak and then only in response to temp. Camphor laurel, walnut, fringed wattle, and a couple of others that I can't think of have not done the same thing.

I neglected to say that my probs were all with oak... I felled an old oak (unknown type) some time ago and the grain is ... well... bland's the best I can say for it. So I used it for items (like the afore-mentioned lidded boxes) that were stained or painted and more mundane items such as jam chucks, sacrificial blocks, etc.

I don't think the humidity changes enough overnight here to change the timber's MC that radically... like you I put it down to temperature. So, yes I have had your problem. :)

[powderpost]

If I make a lidded bowl now, it is rough turned and thrown under the bench for six to eight weeks and then finished off, even if the timber is well seasoned. This allows the timber to settle down and movement is minimised. And even then there are no tight fits. This is one of the many reasons I have gone down the laminating track. Highly figured and "dificult" timbers are easily tamed, and it is more challenging.
Jim