Table top flattening

[Wouldchuk]

Hello all.

I've been making a small table, which will have a drop leaf, and will sit up against a wall.

The top I made from 1inch planed American white oak which i'd bought ready-planed and were straight and true at the time when I biscuited and butt-jointed them together. The top is around 800mm by 450mm, with the drop leaf 800 x 300mm.

In the long lag between getting on with the job, the time spent in the workshop has led to the glued-up top cupping significantly, with around 5 - 10mm of deflection from the centre. The top is cupping upwards, creating a 'bowl' like shape if that makes sense (although it's obvoiusly not that bad!). If you run a straight-edge across the width, and measure down to the centre, there is 5mm or so deflection.

I'm now pondering how I correct this - there seems so much deflection that if I plane the edges down until level they will be quite a bit thinner than the centre. But is that the only option?

I was thinking of making a simple router sled and using it overhead.

Advice?

 

[Mike.S]

How's the table top been fixed to the base (can the top be flipped over?) and has the drop leaf part also cupped?

 

[Jacob]

I'd leave it somewhere at room temp for a few weeks and then plane it flat and re-make it. It'll be thinner but tops are often thinner than you'd think - concealed by thumb nail mouldings etc.
You could consider just flattening the convex side as the top and leaving a hollow on the underside, out of sight.

 

[Wouldchuk]

It was not fixed to the base at all, but unfortuantely the other side has a big imperfection so wouldnt work if flipped over.

The wood was stored in a barn, so under cover but very much outside temperature - and as you know we've had a fair bit of rain of late...! then it went into the workshop, which isn't heated, but is possibly a touch warmer/drier.

I could take it in the house and let it stabilise in there for a couple of weeks then tackle it again - at 1inch thick I do have a bit of leeway as the other components are around 20mm thick so going down to that wouldnt look out of place.

Which side to go at first - I was thinking of clamping it flat topside up, then running the router over to take down the cupped edge 'wings' to level, then turn it over face/top down, and take off some material from the underside to even it all out, then finish it with smoothing plane and scraper to get a better finish.

Thanks

Tim

 

[Myfordman]

Yes take it indoors in the final location for the table and see if it becomes acceptably flat. If not rip it down the middle, joint the cut edges and re-glue it keeping it indoors. A small amount of planing may still be needed but much less than at the moment.

 

[bugbear]

The wood was stored in a barn, so under cover but very much outside temperature - and as you know we've had a fair bit of rain of late...! then it went into the workshop, which isn't heated, but is possibly a touch warmer/drier.

I could take it in the house and let it stabilise in there for a couple of weeks then tackle it again

There's no point trueing it at anything other than the humidity it will finally be in - if you make it dead true at the moment, and it WILL be a banana in your house. The one thing you know about this piece for sure is that it moves with humidity changes.

Correct the humidity, and proceed from there.

BugBear

 

[dzj]

Kerf cuts on the underside of the table and breadboard ends.

 

[Wouldchuk]

I had thought about fitting bread board ends, although the issue is that while I could do it on the main top, the drop-leaf wll be curved and so wouldn't work, unless i can make curved breadboard ends?? That's something I've never seen before.

Kerf-cuts could work, I take it that they'd still work even if were not carried right through to the edges, so as not to be visible and allowing me to still rout a decorative edge on the table top.....

 

[Jacob]

......
Which side to go at first - I was thinking of clamping it flat topside up, then running the router over to take down the cupped edge 'wings' to level, then turn it over face/top down, and take off some material from the underside to even it all out, then finish it with smoothing plane and scraper to get a better finish.

Thanks

Tim

The basic rule is best side first, as this is the side from which you want to remove least. You get the best side flat and then thickness from the other side.
I wouldn't fiddle about with a router - there are these things called planes; made for the job.

 

[Mr T]

How many boards are there in the top? I wondered if you had assembled them with the annual rings alternating, happy and sad as I call it, this would help to even out cupping. If you don't want to loose too much thickness you could saw down the joints, re plane them so the surface is flat then rejoint (only after storing the piece in doors for a while). A lot of work, but planing out a 5mm cup will be quite a lot of work.

Chris

 

[marcros]

i would put it inside for a while before doing anything. It may settle out a bit by itself.

 

[Wouldchuk]

Right ho - I use my dad's workshop as I live away with no room, so I'll ask him to take the tops inside and see how they respond to a couple of weeks being inside. If I can get it down to planeable-degree of cupping then I will use the No.7.

The top is three boards, each aroudn 150mm, but due to the imperfection it wasn't possible to alternate the rings - the cahllenge of working with only a very limited supply of wood - I've not much scope for mistakes, which I am somewhat prone to... (hammer)

 

[John15]

Hi,
I built a table towards the end of last year. Unnoticed by me at the time, the top moved to a convex shape, as yours has during the glueing-up process. I asked for help on this forum and was advised, provided there was enough thickness, to plane the top surface flat. This I did, it didn't take much time, and the end result was a perfectly flat table-top.
It was good sound advice from the experts and very much appreciated.

Cheers,
John