Slab Thickness

Hi from sunny Tasmania!

I have a couple of shortish Blackwood logs about 2.4m and 1.8m long. The first one is around 600mm X 750mm average diameter and the second one is similar but tapers to around 400mm X 500mm above the fork. I am considering cutting them into slabs. I am looking for advice about the best thickness to cut them or an alternative cutting plan. I don't have any specific projects planned for the timber, but they are too good for firewood as they are really nice dark stuff.

Simon

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Best thickness is that which you can make the best use of. Each log should be assessed before putting it to the mill. And remain open minded as you start cutting because a sudden change of plan can often arise as fancy grain can become evident in the most unlikely places.

I had some Sheoak slabbed to 55-60mm years ago, and have only just now 20+ years later, decided to work it.

Now I wish I had it slabbed a little thicker at 60-65mm to allow for splitting into two (2) butterfly slabs. :?

Still might split it, but there is little margin of error.

Quote:

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Originally Posted by cava

I had some Sheoak slabbed to 55-60mm years ago, and have only just now 20+ years later, decided to work it. Now I wish I had it slabbed a little thicker at 60-65mm to allow for splitting into two (2) butterfly slabs. :? Still might split it, but there is little margin of error.

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Definitely requires some thought about potential future use.

Wood turners prefer slabs/billets at least 75mm thick for bowl blanks, 100mm for large spindle blanks etc.

Whilst if it is destined for box making you could go as thin as 20-25mm to facilitate quick drying for thin sections.

Also consider value adding any specific grain features - plain grain slab it to gain max return, highly figured grain requires some consideration in cutting as to how to get the best from the features.

Hi XJ9,

I am new to the milling game and Ihave to date milled all my slabs at 50mm thickness for the purposes of my ownwoodworking projects (im an absolute newbie to woodworking). I have found that after drying, I can get anice finished board at about 40mm thick however I cant quite get two 20mmboards out of that slab after resawing. This is largely due to my skills (or lack thereof) when resawing, butthe movement during drying and poor surface finish I get off the mill alsocontribute.


So – for my next few logs I think Iam going to experiment with some 55 or 60mm slabs – as well as some thinnerones at 25mm.

They are nice looking logs you have –im jealous.

Brendan

For table tops and benchtops I tend to use slabs ~32mm these days, so I'd mill to 40mm for that purpose.
And hope and pray that no cupping and buckling kills it.
However, for resawing I'd go more substantial, around the 55-60mm mark for carcass members or boards.

Thanks for the advice so far guys. My initial thoughts were to go for thick slabs at 75mm or more. Now I'm thinking some thick and some thinner ones might be better - say around 40mm like some of your suggestions, maybe a bit thinner. Blackwood loves to move about when it is re-sawn even after drying it for a very long time, so I might err on cutting any potential book matched pieces to thickness as I go. Perhaps Blackwood is prone to build up a lot of stress in the wood as it grows and/or it tends to hold moisture for longer. I know that Blackwood firewood tends to take a lot longer than gum to dry out.

Anyway, I got the table saw out to a wedge piece that I cut off the butt of the bigger log today for an experiment. I have a couple of pictures below of the result with a bit of linseed oil on it to try and show the grain. I have a lot to learn about getting my photos the way I want them, but I think that you can see there is a hint of some pretty grain potential.

Simon


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Stunning timber. I wish I had access to Blackwood. I mostly get stuff sporadically from a mate who is a tree surgeon, which to date has yielded a beautiful redgum and ironbark log. Otherwise I cut stuff at my mates farm for fun/practice which is full of candlebark and stringbark. The stringy seems to produce beautifully coloured timber - but I have heard it can be difficult to dry.

I am keen to mill some 100mm x 100mm posts to use as 85 to 90mm table legs after drying - I am worried about movement and drying times though. I might be better off using laminated 45mm boards.

Interesting comments...
I have rarely had issues with Blackwood 'moving' whilst seasoning and have milled a lot of it
That said i always quarter saw
I would suggest cutting the Butt log where it bends...giving you 2 logs at 1.2m long...that will relieve a lot of internal stress
Will give you more consistent grain too and a better recovery
As for sizes...how long is a piece of string?
All depends what the end use of the timber is going to be
A Butt log of the one you display should yield some nice 215mm wide quarter sawn pieces out the centre (both sides hopefully)
Great for guitar caps/solid bodies...and multiple neck stock!
Or plenty of delightful box making material too
Again...mill on the quarter is my advice...MM:2tsup:

Thanks for the suggestion Mapleman. I think that I have been fixated on making thick slabs and haven't evaluated many alternatives, but you have changed my thinking. I never really considered cutting the butt section in half, but now I am. Probably a good thing it's dark now or I might be out there doing just that. I have spent too long looking at my Dad's Blackwood stack of 4X2s and 8X1s etc that are all really long stuff to consider cutting shorter boards. I know that when my parents were using some of their timber for a kitchen, the company making the doors etc were really cagey about re-sawing the 2" stuff as they reckoned that a lot would warp even though it had been in a dry shed for 20 plus years. They kiln dried it all anyway before using it. Maybe it's just a moisture level thing, I don't know for sure as I haven't tested it to any extent. You are right about the quarter sawn grain too (second picture for anyone not sure), although my photo hardly does justice to the flat sawn side. There's a really nice 3D pattern in there when the light is right, but I bet that it would cup nearly instantly with my luck.

Brendan, those couple of logs were destined for firewood, so it's amazing what you can find sometimes. In the past I have made a few small things from offcuts and pieces docked off timber that was being packed for sale. It's only been in the last couple of years that I have started considering tackling bigger stuff my self. My first bit of real milling experience a few years ago was helping a guy with a Lucas Mill cut up some Brown Top into 100mm X 50mm for a shed roof that I hope to get built soon. Even though I've been around a lot of stacks of timber, that experience really peaked my interest. I suppose that I just got a bit more addicted to the hobby and like you, I'm out to learn everything I can from the vast experience on this forum.

I'm not sure how Stringybark goes in the drying process, but generally the thicker the timber is, the longer it takes to dry - so cut some 100mm X 100mm (or bigger if you dare) posts if you get the right log, stack it carefully with lots of rack sticks and put some weight on the stack. Then, forget about it for a while, it will come in useful when you least expect it. I bet some nice heavy pieces of Stringybark would make great table legs and bigger stuff would be fantastic staircase posts. One thing for sure, you wont know till you try.

Simon

Your Butt logs will produce quite a few quarter sawn 125mm wide boards if you mill vertically from top of the log
As well as 125mm squares off the sides
Then,because of the lay of the grain,mill horizontally and get a host of quarter sawn 175mm-215mm wide boards from the centre
Should be able to get quite a few quarter sawn 100mm-125mm wide boards milling vertically from below the heart, to finish
(as well as squares off the sides)
Or leave as a chunky round back and resaw into a 65mm-75mm thick slab,also cutting a line of 25mm square blanks for stripping out...MM:2tsup:
(if using a swing blade Lucas Mill)