Attaching a table top

[Zachary Hancock]

Good day,

Long time lurker but one of my first posts.


I am building a slightly modified version of this table for my wife and I am to the point where I am about to connect the table top to the bases. One significant difference is I made the top of of 5/4 Ash glued into a solid piece. My concern is wood movement. Based on the fact that there are no aprons, and really two support bases that I can attach the table top, how would you guys recommend doing it to avoid the top moving and cracking? From what I understand the movement would be an expansion across the width of the table, which is why the perpindicular-to-the-grain mounts of the bases are a problem.

This is my first major build for the wife and I dont want to screw it up!!!

Thanks!!!!


http://www.ana-white.com/2012/06/pla...armhouse-table

[Doug Hepler]

Zachary:

I can't quite picture your design. Is it like a trestle table with support at each end and no aprons? I'm going to assume that. If the legs are not attached to each other acros the width of the table, as they would be by aprons, etc., then the top will move freely and you have no problem.

Dimensional change with seasoned wood because of changes in relative humidity (RH) is mainly across the grain. Movement with the grain is negligible. You can find tables and formulas to calculate likely dimensional changes but they are often not necessary. If the table top is 36" wide, you could have as much as an inch of change in the width of the top. This is probably a great overestimate because it assumes a 50% change in RH from what it is now to what it would be at some time in the future. But, it's possible if the table is in in Nova Scotia in a heated shop now and will be in 90%+ RH this summer. You get the idea? Also, if the attachment points are closer together than 36" the possible dimensional change between them would be proportionally less.

So, you need to let the attachment point at one side of the top move as much as the expected dimensional change. (You can attach the other side as you wish.) There are many ways to hold a table top down on its base and still let it expand and contract. You can buy metal table top clips that screw to the top and run in a slot on the base. You can make a slot in the attachment point in the base and pass screws through the slot into the top, so that they can slide back and forth. You can make two cleats that can slide past one another while holding the top against the base.

I hope this helps. Write back to the forum if you have further questions. Since you have been "lurking" you already know that SMC is a pleasant bunch of people who like to help.

Doug

[Zachary Hancock]

Thank you for your reply. Attached is a very close idea of what my final build will look like. You will notice that the table (96" long at 36" wide) only makes contact with the bases at the very end of the table. The lateral support beam running across the middle does not make contact to the top at all.

My concern was simply that since the table top is only fastened to the two bases to a piece of wood that runs cross-wise against the long grain of the top, that the seasonal expansion of the top will be hindered and cause a breakage. Does that make sense? I am trying to explain it as well as possible but am not sure I am doing too great of a job.

[Matt Day]

I've built a few trestle style tables and have used z-clips. I cut a kerf using a thin kerf TS blade on each face of each leg. Since it's only about 1/2" from the top, it won't be seen unless you're looking for it. Screw one end of the clip to the table top and the other end can move with seasonal expansion.

[Hoang N Nguyen]

Z brackets are what I use to secure my table tops to it's legs/base. You cut a slot near the top of your legs, 1 end of the Z bracket goes into the slot and the other gets screwed into the table top. It pulls the table top to the legs holding it in place while allowing the table top to move width wise along the slot. I use my biscuit joiner to make the slot and it makes easy work of it.

http://www.rockler.com/table-top-fasteners

Those are what I use, I'm sure you can find others like it elsewhere.

[Zachary Hancock]

Very interesting. Do these provide enough support to be able to lift the table by the top? I assume so if you use enough, is this correct?

Z brackets are what I use to secure my table tops to it's legs/base. You cut a slot near the top of your legs, 1 end of the Z bracket goes into the slot and the other gets screwed into the table top. It pulls the table top to the legs holding it in place while allowing the table top to move width wise along the slot. I use my biscuit joiner to make the slot and it makes easy work of it.

http://www.rockler.com/table-top-fasteners

Those are what I use, I'm sure you can find others like it elsewhere.

[glenn bradley]

With that rustic look and base-member scale you could counterbore, use an oversized through hole or slot and then screw into the top from below.


lag screw table attach.JPG

[Hoang N Nguyen]

Very interesting. Do these provide enough support to be able to lift the table by the top? I assume so if you use enough, is this correct?

Yes they do and they have no trouble doing so. If you check out the woodworking projects section of the forums, you'll see I posted (in 2 different threads) the dining tables I built. Both tables are held onto the legs using the Z brackets. Although my tables have aprons, you can just as easily attach them to your legs only.

I have lifted the table and moved it by just holding onto the top and the brackets held the legs just fine.

Edit: here are the links for you. Mind you these table are stupid heavy.

http://www.sawmillcreek.org/showthre...a-Dining-Table
http://www.sawmillcreek.org/showthre...a-dining-table

[Matt Day]

Glenn's suggestion is a good one as well. You could also use threaded inserts with this method. The thicker the material the more cumbersome it can be though, and it looks like it might not work at all if you have those angled braces.

Z-clips are pretty strong little buggers. I usually space them around 6-8" apart I think but tailor to suit.

[Zachary Hancock]

Thanks so much for all of the suggestions here.

I will keep you all updated on the progress!!!!

[David Eisenhauer]

Genrally speaking, table tops can be fastened to a base structure by a single fixed point located at the center of each end of the table top, then fixed along the width of the table top ends by sliding points. By fixing the top at the center point, the expansion works from the center out towards each end. You fix something that does not move at the center, then fix the remainder of the width with something that allows for expansion/contraction (sliding). Using Glenn's drawing, you could screw the top from through the underneath of the cross stretchers at the center of the table top width (same size screw hole diameter), then use slotted holes (as in Glenn's drawing) as you screw the top down moving away from the center. 36" top that heavy looking would probably be better off with around five screws per end, but you will be better able to judge that than I can from where I am sitting. The Z fasteners are very popular for attaching somewhat lighter table tops down to the base and work very well, easy to install. You can buy a box of 100 of those and keep them for lots of projects.

[Charlie Fox]

i am a bit of an unconventional builder. i have built 2 farmhouse tables - different style than yours, and i built them so that the table just sits on the base. the top is all pocket-screwed, no glue, made from tongue and groove antique flooring, i had the idea that maybe each piece would move on its own as opposed to the entire field and i think that has happened. i can tell there has been some movement because the ends of the tongue and groove on the breadboards are no longer flush. each table has gone through several seasonal climate reversals and no problems. on the bottom of the tabletop i just used short 1x1 pieces to make an insert for the top of each 4x4 leg to fit in. if i made a table your style i would do similar - add a 1" tall "peg" on all four corners and add an insert to the corresponding locations on the bottom of the table top - basically building a surface mortice. we have had dinners with 14 people as well as numerous domino games and they are plenty solid.

FHtable1med.jpgleahtable2.jpg

[Phil Stone]

That's a nice looking table, Charlie.

[Charlie Fox]

thanks - but its two tables :-) - one 6' the other 9.5' (right). from flooring from tear downs in Houston, 80-100 yrs old.

[Phil Stone]

Yeah, they're both beautiful, but I was transfixed by the left one when I replied!