Dealing with compression while milling timber

[Rhob the Log]

Starting to get a little daunted by the amount of movement in the timber I'm milling Started with sweet chestnut, which peels away badly from the band. Today, both Ash and Oak started doing the same. The Ash was probably growing on a lean but was perfectly round and straight stemmed and the Oak was pretty straight growth too.

 

Any of you other millers found a way to deal with this? Any signs to recognise it in the end grain? (See the Chestnut pic below)

 

I've tried clamping the cut board and cant together with F-clamps which works reasonably well and the Norwood manual says to keep rotating the log and taking cuts from opposite sides. Is it just a case of flattening them out over the drying process?

 

Any help appreciated. Cheers!

[agrimog]

once you find out how to stop it moving, let us all know, just when I think I've got it sussed, the next bit I mill does what it likes, lay it flat, sticker it well, and weight it down and hope it dries flat.......good luck

[Big J]

I tend to mill pretty big lumps, so don't get too much in the way of tension. Smaller logs are far, far worse for it. The worst one that I have had in recent times was a lovely straight beech I felled and milled earlier in the year.

 

It was to all intents perfect - 85ft tall 23" DBH, gun barrel straight and 4x12ft products off it with no twigs until 30ft and nothing more than 2 inches at 48ft. It had quite a lot of tension in it though, peeling away as I cut it.

 

Only thing you can do is continue to rotate the log as you cut it, taking even amounts off all sides. You will still have some inaccurate boards, but it's not the end of the world.

 

J

[Copford sawmill sussex]

No tree is the same we get some that don't move and some that spring loads when they do like everyone else says just gotta rotate and trim and trim,

[Rhob the Log]

Nice, cheers Agrimog and J. Glad to know I'm not the only one. Maybe if I understood tension and compression more...

 

Is it the weight of a large tree that forces any fibres under tension to keep in alignment or is it that the older the wood, the less the fibres are in opposition to neighbouring fibres / those on the other side of the round (if that makes sense)? Or have they just relaxed and grown solid after their youthful rush for the sun?

 

Having not done any quartersawn boards, just quartering to fit the processor, how does this affect compression? Peely quarters look pretty difficult to slab out. Too many questions I know...

[agg221]

If there's stress, it's going to move. From personal experience I would say that splitting the log clean up the pith with the first cut takes the most stress out in a single cut. If both sides come out true then you can carry on as you wish. If both sides resemble a banana they can either be trued up and milled, or stood on edge and milled that way. If you do the latter, boards are only half the width but I've found far less movement.

 

Alec

Edited May 15, 2013 by agg221

[Woodworks]

I have never done any milling so take this with a pinch of salt

 

I used to buy my furniture grade planks from a chap who used to take trees from his woodland to kiln dried boards ready for sale. He explained to me once that the best wood came from tress in valleys preferably from the east side of the country. He explained that many trees would grow straight but if they were exposed to the prevailing winds (generally SW in the UK) They would develop tension on the SW side to resist the winds. This is fine when the tree is whole but when planked up these stresses are released leaving you with bowed boards.

[Chunkymunky]

From experience of making things from warped wood there is only so much you can do to prevent it in cutting. Not something i am experienced in but when you stack the planks try putting the bent ones on the bottom. Force them back while they are in a state to do it.

[Big J]

I have never done any milling so take this with a pinch of salt

 

I used to buy my furniture grade planks from a chap who used to take trees from his woodland to kiln dried boards ready for sale. He explained to me once that the best wood came from tress in valleys preferably from the east side of the country. He explained that many trees would grow straight but if they were exposed to the prevailing winds (generally SW in the UK) They would develop tension on the SW side to resist the winds. This is fine when the tree is whole but when planked up these stresses are released leaving you with bowed boards.

 

I'm not sure that that is the case. The aforementioned beech tree exhibited tension in all facets of the stem, not just on one side.

 

Alec - I reckon that even just halving a log takes the majority of the tension out of it. I usually try to take the biggest trees I can find, which all end up halved. I cannot recall the last time I had any noticeable tension in a halved log. There certainly wouldn't be anything in a quarter.

 

Jonathan

[agg221]

 

Alec - I reckon that even just halving a log takes the majority of the tension out of it. I usually try to take the biggest trees I can find, which all end up halved. I cannot recall the last time I had any noticeable tension in a halved log. There certainly wouldn't be anything in a quarter.

 

Jonathan

 

Agreed - hence the first halving cut.

 

Alec