oak and checking / warping slabs

[diesel&coffee]

General question on slabbing and oak..

How bad does oak check/crack and warp?? Is it better to cut 2.5 - 3 inch slabs to help prevent it from warping?? Say if u had 18 - 20" dia or even 35 - 40" dia trunk.

 

[TraditionalTool]

General question on slabbing and oak..

How bad does oak check/crack and warp?? Is it better to cut 2.5 - 3 inch slabs to help prevent it from warping?? Say if u had 18 - 20" dia or even 35 - 40" dia trunk.

Kind of a trick question. Depends on where you cut the wood from in the tree.

The pith has most of the tension, and as such has a tendency to check. If you cut a full section slab, it will in most cases check along the center where the pith is located, if quartersawn.

To get the best quality/grade of wood, it's best to take wood from both sides of the pith, eliminating most of that tension. This is also why it is recommended not to cut full width slabs, and split the log and cut both sides. That will produce the best quality timber. Box heart cuts will be the most stable though, for a beam for instance, but will almost always check because they have the pith inside of them. Most sawyers will tell you that it is almost impossible to keep a box heart beam from checking, because of such.

The interesting thing I have noticed myself is that when you cut a full width slab, it has a tendency to check down the center where the pith is. However, if you leave the log round, the checks have a tendency to spiral and will end up any direction, sometimes facing up, sometimes facing out, sometimes facing down. This is in regards to the quartersawn portion in the center of the log.

I'm attaching a pic which shows this with a section that is basically quartersawn. Notice also that the knots cause the check to happen on either side of it, so that often in a log if you have knots along the pith (spike knots, BTW, in regards to the log) it will break up the checking, often forcing it to either side of the knot. Often it will check on each side of the knot, in opposite directions. These pics don't depict that very well, but you can see how the knot breaks up the check. Look at the checks and knot on the bottom right of the pic, you can see how a check is running off on each side of the knot, which is what I was trying to describe.

 

[diesel&coffee]

thanks!

plainsawn

If one is just using for table tops?? whatever that may mean! Hallway narrow width long top.. Front door table.. Coffee table, etc, etc.. Even work table or bar table..

Not all the slabs would have the pith in them.. But if the dia. of the tree is small then each piece may have some of it in the cut! Just a thought/question..

If plain slabing - then cut the pith out - and glue back together when making the table top?? But then the cool natural grain pattern id gone.. or is it a good practice / and or can one get good results using a clear epoxy filler when making tabletop before staining, etc..

 

[TraditionalTool]

If plain slabing - then cut the pith out - and glue back together when making the table top?? But then the cool natural grain pattern id gone.. or is it a good practice / and or can one get good results using a clear epoxy filler when making tabletop before staining, etc..

That is what I would do if you wanted to make it the most stable, got the slabs down the center, let them dry and then glue it back together. I think you could still match the pieces back up together. If you leave them whole, seal the ends, and sticker them property you can reduce the amount greatly, but I think you will still get some checking.

Most lumber has been cut on the sides of the pith, so that is much less of a problem with the wood you buy at the local lumber supplier, but is also why it's hard to find anything wider than say, 12"-15", which will most likely require a 26"-32" diameter tree (to get a couple boards that width on each side of the pith).

Maybe someone with more experience with oak will comment. I've worked quite a bit of it, but haven't milled any. Have cut a fair amount of it up for firewood, dare I mention...:monkey:

 

[scsmith42]

General question on slabbing and oak..

How bad does oak check/crack and warp?? Is it better to cut 2.5 - 3 inch slabs to help prevent it from warping?? Say if u had 18 - 20" dia or even 35 - 40" dia trunk.

I routinely mill large diameter oak trees and I also operate a kiln. As others have indicated, some checking is due to the pith wood - try to avoid having it in your finished boards/planks.

Oak is extremely slow drying - maximum recommended daily drying rate for 4/4 oak is 3%. 8/4 is around 1.4%, and 12/4 is less than 1/2% per day.

The biggest challenge that most folks have when air drying oak is that they allow it to dry too quickly when it is first milled. Slow, steady drying from green down to 35% MC will prevent just about all of the drying related problems from occuring. Once you are below 35% MC, it is not as critical.

Oak does not warp any worse than other woods, as long as you pay attention to the early drying. There is an exception though - and it is more prevalent in Texas, and that is live oak. Typically LO has a lot of internal stress and it moves all over the place while drying.

What particular species of oak are you inquiring about, and as to thicknesses what are your intended uses for the boards?

Scott

 

[diesel&coffee]

What particular species of oak are you inquiring about, and as to thicknesses what are your intended uses for the boards?

Scott

Bummmmmmm - San Antonio/hill country is Live Oak central! There other as you get into the hill country.. But I really don't know/or can tell the diff..

As for the thickness - for tabletops.. Whatever that may mean.. Narrow, wide, low, high, using black iron pipe as legs... Mesquite wood blocks like dowel rods to attach the pipe under the top... the dowel rod part of the mesquite block coming though to the top..
just brain storming here..

Drying - will a garage do? Thats all I got.. It's not in the sun!

ps: where are u in NC.. My sister lives in Charlotte.. Maybe if I come that what way I can find you - I would love to get just ONE or TWO big trunks to mill.. I could mill it right there!

 

[scsmith42]

Bummmmmmm - San Antonio/hill country is Live Oak central! There other as you get into the hill country.. But I really don't know/or can tell the diff..

As for the thickness - for tabletops.. Whatever that may mean.. Narrow, wide, low, high, using black iron pipe as legs... Mesquite wood blocks like dowel rods to attach the pipe under the top... the dowel rod part of the mesquite block coming though to the top..
just brain storming here..

Drying - will a garage do? Thats all I got.. It's not in the sun!

ps: where are u in NC.. My sister lives in Charlotte.. Maybe if I come that what way I can find you - I would love to get just ONE or TWO big trunks to mill.. I could mill it right there!

I'm about two and a half hours east of Charlotte.... and I used to live on a ranch about two and a half hours west of San Antone in Real County... Yup, that is live oak country.

If you're after the "slab" look, then consider slabbing them around 3" - 4" and sealing the ends. They will dry in a decade of so.... <grin>.

It's usually not a good idea to slab, dry and resaw, as you will get a pretty good differential in moisture content between the core and the shell, and you'll warp for sure after resawing. If your design is rustic enough, you may be able to compensate for the movement.

In a perfect world, I would advise you to mill the log in October; that way the first several months of air drying (and most critical part) will be during the cooler season, when the wood is less apt to dry too quickly. In general, spring time is not the best time to mill oak slabs because of the upcoming hot summer and it's impact on the drying rate.

 

[diesel&coffee]

I'm about two and a half hours east of Charlotte.... and I used to live on a ranch about two and a half hours west of San Antone in Real County... Yup, that is live oak country.

sent u a priv. msg - hope u log on soon!