Controlling movement in Milled slabs.

[Squaredy]

31 minutes ago, Retired Climber said:

Presumably the increase in value of very straight / stable timber would not cancel out the wastefulness? 

 

Could you put the planks through a planer / thicknesser? 

No.  

Yes you can use a thicknesser but it would need to be a very wide one.  Most are only 18 inches or two feet wide.  A good wide slab will often be wider than this.

[Rob D]

3 hours ago, Retired Climber said:

Forgive my lack of understanding of the subject; I know roughly the square root of nothing about milling. 

If flat, straight boards are valuable, is it not worth cutting slightly oversized, drying them, and then cutting them to final size to take out any distortion? 

 

I do realise I'm probably misunderstanding the problem, but can't work out how. 

 

 

It's a big question - there's a lot to it and to understand it all I'd say is around 4 hours worth of info. It's to do with how wood grows/how it is cut/where the rings are/how fast it is dried/through sawn or quarter sawn - like sharpening a chainsaw or dismantling a tree. You need to already know a certain amount of info to understand it.

[Retired Climber]

4 minutes ago, Rob D said:

 

 

It's a big question - there's a lot to it and to understand it all I'd say is around 4 hours worth of info. It's to do with how wood grows/how it is cut/where the rings are/how fast it is dried/through sawn or quarter sawn - like sharpening a chainsaw or dismantling a tree. You need to already know a certain amount of info to understand it.

I have a good understanding of how trees grow, the forces that act upon them before and after they are cut and the reasons why they warp and bend; I just couldn't really understand why they couldn't be cut roughly, left to do their thing, then cut to size. 

It would seem that it's simply not financially viable, for a number of reasons. 

[openspaceman]

4 hours ago, Rob D said:

This is the best method I have found to date - as everything matches up perfectly and gives maximum support. It needs to be refined [and another idea is to mill to say 3" or 4" - allow longer to dry - then re saw the planks afterwards if you need accurate 1.5" etc.

 

Full video on the process here - I checked back a year later and it seems to be drying very well.

 

 

Good to see the stickers  flush with the ends of the boards too.

[Rob D]

3 hours ago, Retired Climber said:

I have a good understanding of how trees grow, the forces that act upon them before and after they are cut and the reasons why they warp and bend; I just couldn't really understand why they couldn't be cut roughly, left to do their thing, then cut to size. 

It would seem that it's simply not financially viable, for a number of reasons. 

 

 

Ah ok fair enough - you could do it - but it's more down to time - in that if you say cut to 4" as a rule of thumb it would take around 3-4 years to dry. But if you had the time then what you are suggesting does make sense. I often saw to 4" and then re saw at a later date.

 

[Rob D]

Another slight issue with sawing oversize is that you can get more tension in the plank - depending on how it is cut and species - so a nice flat looking 4" piece after cut into x2 1 3/4 pieces - after cut they can move and warp as they no longer have the same support that was present in the 4" piece.

 

But I have a some horse chestnut I am cutting at the moment into 4" slabs - to dry in situ - then re saw in 2 years as 2" or just under. Will see how that goes.

[ucoulddoit]

3 hours ago, Rob D said:

so a nice flat looking 4" piece after cut into x2 1 3/4 pieces - after cut they can move and warp as they no longer have the same support that was present in the 4" piece.

 

Sounds like case hardening caused by drying too quickly if the two thinner boards cup significantly. I find the old rule of thumb for air drying of a year per inch thickness plus a year for hardwoods up to about 4" thickness works pretty well, regardless of what the moisture meter tells you sooner. I remember seeing a kiln dried perfectly flat plank of lovely walnut being ripped into two thinner boards which cupped so badly it had to be thrown away!

 

And there are other issues to consider. How many folk use 1/2" stickers for oak for instance instead of the usual 1"? That helps to slow the drying and also avoid other defects such as surface checking and internal honeycombing.

 

Further drying after air drying also needs to be slow and dehumidifier kilns are better for this than a steam kiln. But only a small proportion of wood will be split into two thinner boards, so that's not a reason to be negative about steam kilns.

 

Overall, I'd say, it's a matter of pre-planning which boards will be milled thick, for future re-sawing, and dry them accordingly. That's what I do, but only on a small scale for my own use. I've found it works well and gives good flexibility to re-saw for designs that have not even been thought about when timber is first milled.

 

Andrew