Won’t stay square
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- This topic has 3 replies, 3 voices, and was last updated 6 years, 6 months ago by lattice.
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I recently bought two slaps of “Wenge” for a display case project. The slaps are roughly 1400 x 300 x 45 (mm) and are flatsawn. The case will essentially be a cube with all glass sides and a wooden frame. I want the frame to be made of approximately 40 mm x 40 mm material. For this I have ripped the sides of the slaps into riftsawn rectangular strips.
I am now trying to dimension the strips and this has proven more difficult than I had anticipated. I can get them square but after a couple of days they are out of square again – not by a lot but more than I feel confident using for joinery. As a hobbyist woodworker, I only have a few hours here and there for working on this project and simply doing the dimensioning and the joinery in one go is not really an option for me.
I figure the issue is moist and wood movement or maybe internal stresses in the wood. According to my moisture measuring device, the wood is at about 11% in the end grain. My cheap moisture meter cannot get an accurate reading on the center of the board due to the hardness of the wood.
Any ideas on how to overcome this problem of mine will be greatly appreciated!Thanks!
- This topic was modified 6 years, 6 months ago by lattice.
8 November 2017 at 8:10 am #359076As someone fairly new to woodworking (1 year!) I find myself coming across this, but/and you can caveat all my comments below with that very limited experience!
My wood is stored in an unheated slightly ventilated garage and I too tend to have to pace my projects – meaning the cut to glue time may be weeks…
I don’t have an ‘answer’ per se, but I do tend to rough cut and dimension and then store the pieces indoors for a few days before final dimensioning, soon after which I try to do the joinery.
Then they stay indoors until I’m ready for glue up, and then again until finished. My limited experience is showing that (a) they’re staying fairly stable from dimension to glue up, and (b) they don’t show any noticeable sign of moving subsequently.
Some timber left in the garage does exhibit radical cupping, bowing, warping and winding and anything else I’ve left out. I’ve had to plane 15mm softwood down to under 12 for later (2 months) use.
I’m finding the hardwoods more generally stable, but they do move over time depending on how they’re sawn and the specific grain direction(s).
I’m no expert on wood types, but I wonder if, although you’ve endeavoured to get as close to rift sawn as you can for obvious reasons, the grain is wavy or interlocked?
The ratio of tangential to radial shrinkage for Wenge is about 1.6 so not extreme, although if the grain is a bit wavy that will give some twist – which since you say ‘square’ and not ‘size’ I assume is your issue.
What I do know from my engineering days is how the relative humidity affects the equilibrium water content of the wood: in our houses where we see a range from 25%-75%, the actual wood moisture content gets driven back and forth by 5-10% – which is a lot.
Your 11% sounds fairly normal for ‘delivered’ timber, and from everything I have read, it seems working with timber which is intended for interior use ideally wants it drier than that.
So, if there is any ‘answer’ perhaps holding it in the final environment before working it is a way to try?
When you have finished dimensioning, and want to store it, even if it is just overnight fully wrap it in cling wrap. This avoids moisture content changing. Hope that helps. Check for instance when Paul is making the chest of drawers, he had wrapped his dimensioned stock there in the first episode.
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