25mm top and add 25mm thick closed grid for strength and a faux 50mm...
arrange the grid to reinforce the table legs..


.

 

Alan, I made a table top for a lady and it was so heavy, two of use could hardly pick it up. It was made from hard maple. The final thickness was just shy of 1 1/2 inches. Seems like it was about 39 x 65 inches or something like that.

I had to glue up the boards in several sessions. It dwarfed my poor little work bench. But she loves it.

 

Mike - I looked at your first picture and wondered why you had full 2 x's clamped to your workbench - and then when I looked at it more closely, realized that those are some large frikken clamping cauls!!

Nice looking table, but given the width of your material (seems to be 5 @ roughly 8" across), what have you done on the underside to prevent warping?

Do you have a picture of the underside?

Thanks

 

4x4's. It's all clamped together. :grin: And it turned out good.

 

I would agree with Stick that 25mm would be a minimum and probably around 35 a maximum. Be aware that boards that wide will be prone to warpage as someone else mentioned. One way to help prevent that is cut saw kerfs into the bottom of the boards about 25 to 35% of the top thickness and I would go about 30 to 35mm apart. This helps to release some of the stresses in the board as it changes temperature and humidity.

You also have to allow for changes in board width as their moisture contents change from season to season. I usually make my tops to sit on a frame with aprons from leg to leg and use these Tabletop Mounting Clamps - Lee Valley Tools to attach the top to the frame. This allows enough movement to prevent cracking of boards or joints. A woodworking friend of mine prefers to make his out of wood but the principle is the same. Here is another method of attaching tops: Expansion Washers - Lee Valley Tools Same general idea in that it allows the connector to slip as one side moves against the other.

I would personally avoid having the legs go through the top. I would want a member between the legs cross ways for support, otherwise you are depending on glued butt joints to hold the weight up and the cross member wouldn't allow for expansion and contraction. Maybe someone elses experiences are different than mine though.

 

I would personally avoid having the legs go through the top. I would want a member between the legs cross ways for support, otherwise you are depending on glued butt joints to hold the weight up and the cross member wouldn't allow for expansion and contraction. Maybe someone elses experiences are different than mine though.

could faux the leg thru the top look...
edge spline the boards together for a major plus....

 

Chuck, I'm with you on not having the legs go right through the top. My reason is that the top wood will move more than the leg wood, because the grains will be running 90º to each other. So you might end up with a leg either protruding very slightly or receding very slightly from the top surface of the table.

Unless you want an arts and crafts type appearance to the top, then in that case you could deliberately have the legs protrude 1/4" or so.

As for the top construction, I think I would be inclined to go for a box type setup as suggested by Señor Stick. That helps keep the table flat and you can use considerably thinner wood for the top without it being obvious.

 

MT Stringer, you have come through again for me! First the adjustable table and now this advice on a table top. Starting on the table for SWMBO real soon. First the planing and cutting to size. Your advice gives me some direction as how to do it.

 

I made a 40X84, 5/4 X 5 1/2"clear pine Tressel table years ago . it was a knock down table with a top,2 X legs units and a 3x6 tressel with 2 x end wedges.
I just glued it together with TB II, no splines Also put a 1" wide bull nose edge strip around the whole table
, glued the edge strip and screwed and plugged the holes at 12" centers.
The top was too heavy for one person to lift alone.
Once in place it was never moved.

Herb

 

Exactly like that. Probably more than 50% of the time I'm mainly using the spline for alignment and the little extra added strength is a bonus but in this case strength is the the most important reason to use a spline.

 

¼'' BB (15/64 actual) works really well...
stable and strong....
Freud # 63-161..
Freud Slot Cutting Router Bit - justfreud.com

 

Would biscuits be good enough here?

 

not really...
good for alignment bit that's about it...

 

Just a thought. My table top was heavy. It wasn't attached to the frame at all. It just sits there.

What I did was make some blocks and sent them with the owner. I told them the turn everything upside down with the top on the floor. Position the frame and then screw the blocks to the top (inside of the frame) using wood screws...and leave just a little space for movement. And they did, and it is apparently working just fine. Been about 4-5 years now. I did hear from her dad last year that she still loves her table.

Note: Hubby was a pseudo carpenter of sorts, but not a table builder. So he had no problem installing the blocks. The top has no where to go because the blocks have it captured.

Note2: I made a promise to myself NEVER to build another one that big and heavy. That was in 2012...and still holds true to this day.

 

Alan, how can I say this diplomatically.....:grin: :grin: :grin:

Sometime the "Director of Home Economics" has to abide by Rules of Wood Working..........VBG.

The table you mentioned (2.5 x 1.2/1.4) would be very heavy unless you build it as a torsion box which I believe Stick has suggested.

If not, then various methods have to be used to prevent twisting and warping.

IMO, plain planks would need to be about 35mm thick.

Be guided by the team, they have experience on their side....

 

Thanks guys. Lots of good info here especially with regard to wood movement. A small amount is not an issue as it is intended to look a bit farmhouse/rustic. I'll work on pushing the "Rules of Wooodworking" James- even at my age things heal (just take longer)

Can you clarify what you mean by "Faux" for the legs. I know it means false but no idea how it works in practise.

Being new to woodworking I always feel a right Numpty asking questions that to others might seem basic but the replies here show me tht even the more experienced can learn. One of the great things about woodworking, like my other interest woodtunring, is that you never stop learning. I just wish I had started to take a bit more interest when younger rather than at 72 years of age.

 

Alan in this case faux means cutting some short pieces that look like the ends of the legs and attaching them into sockets in the table top. They would look like through legs but the actual legs would terminate at the bottom surface of the table.

 

Thanks Charles, Its as I thought.

Good news is that the design brief has changed to more conventional pedestal/trestle style legs.

Now to get things under way before the design brief changes again