Question about warped slab. PLEASE HELP

How long have you had the slab, and have you allowed it to equilibrate in the shop environment?
Big slabs such as yours will require some time to “settle”. After that, they will need to be hand planed. Even then they will wiggle more.
You’re in for some time and effort.
If you’ll PM me, I can give you a name of an excellent woodworker who may be able to help with your challenge.
No guarantees for sure, but he might be able to offer some wisdom.
Bill

-- [email protected]

Is that a 3000/5000 watt heater i see?

Beautiful slab !
Downside: Unfortunately solid wood moves with change in humidity..”moisture”.
You may end up with cracks andchecks as well as time goes on !
If your clients are aware of this it wont be much of an issue.
You might be able to make “kerf cuts” on the underside to relieve the movement.
The market here…..people are actually looking for tables with some imperfections…...they think its character !
If it were my build….I would try to make it as flat as possible in my shop…..what happens after is the clients !

-- "My mission in life - make everyone smile !"

The only remedy I have used is to put a 1” blocks on the sides that touch and one on the middle, clamp the other two sides so they go below 1”. Every few days relieve the pressure and see if it has corrected itself. It looks like the slab is about 2” thick. If so, it should work out fine.

-- earthartandfoods.com

Without battens screwed to the underside or breadboards pinned to the ends I think that degree of warping is to be expected. The good news is that you may still be able to pull the table top flat with battens or bread boats and it should remain fairly flat thereafter. I’ve used these reviewing several times.

To answer your question, BrutDesign, a DR table with one corner more than 1/32 inch higher than the other 3 would press my standards as being acceptable. I personally think most customers would not notice 1/64 and would make it so—even a live edge slab.

-- I dream of a world where a duck can cross the road and no one asks why.

Is that a 3000/5000 watt heater i see?

- DirtyMike

Yes it is. Is that good or bad? haha. I didn’t know that heater had any fans

-- Gerard Williams, Founder: Brüt Design

To answer your question, BrutDesign, a DR table with one corner more than 1/32 inch higher than the other 3 would press my standards as being acceptable. I personally think most customers would not notice 1/64 and would make it so—even a live edge slab.

- MNgary

Thanks for your input. That is quite an exacting standard, but it is good to set the bar high! It’s looking like I’m going to have to flatten the friggin’ thing. Would have been nice to just clean the edges, sand with 220, and finish.

-- Gerard Williams, Founder: Brüt Design

Without battens screwed to the underside or breadboards pinned to the ends I think that degree of warping is to be expected. The good news is that you may still be able to pull the table top flat with battens or bread boats and it should remain fairly flat thereafter. I ve used these reviewing several times.

- JoePowers

Battens are a good idea but I don’t think it goes with the look of the table!

-- Gerard Williams, Founder: Brüt Design

Beautiful slab !
Downside: Unfortunately solid wood moves with change in humidity..”moisture”.
You may end up with cracks andchecks as well as time goes on !
If your clients are aware of this it wont be much of an issue.
You might be able to make “kerf cuts” on the underside to relieve the movement.
The market here…..people are actually looking for tables with some imperfections…...they think its character !
If it were my build….I would try to make it as flat as possible in my shop…..what happens after is the clients !

- canadianchips

Thanks! yeah, once it leaves there is really no telling what will happen. It’s a little bit hard to explain that to people with no experience with wood/wood movement, but I suppose they’ll learn! Interesting idea with the kerf cuts. I’ve never heard that.

-- Gerard Williams, Founder: Brüt Design

Is that a 3000/5000 watt heater i see?

- DirtyMike

Yes it is. Is that good or bad? haha. I didn t know that heater had any fans

Hopefully good, I am still waiting for mine to ship. Sorry i am no help with your slab troubles, I feel you pain. Like others have said slabs move and it is very frustrating. good luck and welcome to lumberjocks

- BrutDesign

BrutDesign,

I suppose the question as to whether a top ½” out of flat is good enough to pass on to a client goes to whether this would be acceptable to the client and perhaps more importantly, to whether it meets your personal standards. But since you are asking whether a ¼” out of flat on two corners is good enough and your other comments, I suspect this slab does not meet your standards.

My guess is that at some point the slab was flat as advertised. But since then it has been improperly stored so that air could not circulate freely around the entire slab. I doubt that any effort to mechanically force the slab to flat will work. It is my belief that the forces in the wood are too great to be overcome mechanically. If the slab has been properly stored since arriving in your shop and remains warped, I can think of three ways to bring the slab back to flat.

The first is a lot of planing and sanding, which would reduce the thickness of the slab by ½”. This would be a lot of time and effort with pretty much guarantee unacceptable results; a flat but thinner slab.

The second option is canadianchips’ kerf method. While deep enough kerfs would allow the slab to flatten out with mechanical fasteners or mortises and glue, saw kerf cuts visible on the ends could be unacceptable. If the kerf cuts are made with a core box router bit, the kerfs would look nicer on the ends. The photos are of outdoor tables where I added core box bit kerf cuts 1/3 of the thickness of the top deep on the lower side of the tops. These were added to keep the originally flat tops flat; not make warped tops flat. In your case the depth of the kerfs may need to be a little deeper. Hopefully there is enough detail visible to show how this style of kerf cut look.

End table,up side down…

Coffee table with core box kerfs showing on the end…

The third method is to rip the slab into narrower boards, joint the edges, and glue the slab back together. But this method has its risks. If stresses exist in the slab, ripping free narrower planks could result in twisting and warping. Warping or twisting of individual planks could require face jointing and planing. Even if the method is successful, the width of the slab would be reduced by the total of the amount removed by ripping and jointing.

Long tapered maple shims could be noticeable, but without knowing more about the base and the method for attachment, it is difficult to say whether shims would be acceptable. Mortising the top to the metal base seems to me could impede wood movement and if so, could result in the top cupping or cracking.

Dear Brut Design, Most of my wood looks like two-bladed propellers before I start. I would cut it into several lengths, plane them flat and then glue them back together. For each piece, use a planing sled such as a piece of heavy plywood, particle board or a bi-fold door. Using hot-glue, tack down the 2 touching diagonal ends then glue wedges along the board so the planer can’t push it down. Put it through the planer, and when one side is flat, knock it off the planing sled, and do the other side. When gluing everything back together, use biscuits every 12 in. Sand flat with a belt sander using a circular motion.
I hope this helps Ken, aka Pook ( A stupid nickname I’m going to change.)

http://lumberjocks.com/topics/192658#

-- West Van Ken