# Best way to build a large table top



## daveedoe (Dec 1, 2012)

Hello,

This is my first post. A buddy of mine bought a ton of 3/4 in. walnut and wants me to build him a large dining table (54 in. X 108 in.). I'm wondering about wood movement. If I glue up the 7 or so boards edge to edge with biscuits, will it hold together for years to come? Should I use pocket screws underneath? Should I do tongue and groove and just frame it in to allow movement? Something else? Any suggestions would be really appreciated. 

Thanks!

David


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## woodnthings (Jan 24, 2009)

*hello dave*

First off the biscuits will not add any strength.
Glue joints are all you need.
The biggest problem you will have is aligning the boards perfectly flat during the glue up.
This can be done several ways.
A glue joint similar to a tongue and groove can be routed on the edges OR you can use straight, stiff boards, called cauls across the boards IF you glue them all at once.
Or you can glue them in sub-assemblies 2 or 3 at a time.
You will need long clamps.
The glue joint helps in aligning the boards, but is a bit trick to get the height correct AND the boards must be planed to the exact same thickness.
http://www.routerworkshop.com/gluejoint.html
Welcome. :yes:
Take a few minutes and introduce yourself in the Introduction section of the forum.
 bill


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## woodnthings (Jan 24, 2009)

*hello dave*

First off the biscuits will not add any strength.
Glue joints are all you need.
The biggest problem you will have is aligning the boards perfectly flat during the glue up.
This can be done several ways.
A glue joint similar to a tongue and groove can be routed on the edges OR you can use straight, stiff boards, called cauls across the boards IF you glue them all at once.
Or you can glue them in sub-assemblies 2 or 3 at a time.
You will need long clamps.
The glue joint helps in aligning the boards, but is a bit tricky to get the height correct AND the boards must be planed to the exact same thickness.
http://www.routerworkshop.com/gluejoint.html


Welcome. :yes:
Take a few minutes and introduce yourself in the Introduction section of the forum.
 bill


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## woodnthings (Jan 24, 2009)

*hello dave*

First off the biscuits will not add any strength.
Glue joints are all you need.
The biggest problem you will have is aligning the boards perfectly flat during the glue up.
This can be done several ways.
A glue joint similar to a tongue and groove can be routed on the edges OR you can use straight, stiff boards, called cauls across the boards IF you glue them all at once.
Or you can glue them in sub-assemblies 2 or 3 at a time.
You will need long clamps.
The glue joint bit helps in aligning the boards, but is a tricky to get the height correct AND all the boards must be planed to the exact same thickness.
http://www.routerworkshop.com/gluejoint.html
To allow for movement after the top is assembled, just make elongated holes in the apron.
Do not glue long grain stretchers across the width. If you use them drill and screw in the center, but let the ends float in elongated holes.
Welcome. :yes:
Take a few minutes and introduce yourself in the Introduction section of the forum.
 bill


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## daveedoe (Dec 1, 2012)

*Thanks Bill!*

Bill,

Thanks for the great advice. I was aware that the biscuit would not add strength to the joint, but thought it could be a good way to help ensure alignment. I've never used cauls, but those look like the way to go. Do you strongly recommend the glue joint router bit, or is it more of a nice-if-you-can kind of suggestion? If the glue will hold the jointed edges well for years to come, I'd rather not get the bit.


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## woodnthings (Jan 24, 2009)

*biscuits have some issues*

Biscuits may swell when wetted with glue and cause slight humps that are visible in the finish. A full length spline would be better and easier to make a slot than tongue and groove. 
The glue joint bit is either loved or hated by most here. 
It does require a bit of trial and error in the setting the height, but after that it works great. 

There are lots of table top glue up threads like this one:
http://www.woodworkingtalk.com/f5/were-you-glue-up-table-top-32049/ He uses the glue joint bit and has some tips.

A quote from the thread:

_You are right about a joint bit being around forever. I come from a woodworking family, 8 generations long and they have been around as long as I can remember._

_Like you, everyone in the US I have ever spoken to, shy away from them. In Europe, most cabinet makers use them, the way I was taught at 11 years old.

You are also right that once machined, that's it and it is what it is._ _

Boards don't have to be the same thickness though and if they are not, it is possible to get perfect alignment on one face, by measuring and adjusting for each cut. I can get an accuracy of up to 0.001" that way. In the latter case if a board varies in thickness across it's length, a shaper won't do it but a router will._ _

You can also _ _glue up twisted and bowed boards and have them straight after glue-up, using a router and a joint bit, provided you plan the machining carefully.

The reason I have never tried cauls, is because they require more space in my shop to store. In the old days _ _glue was not what it is today, which is why this is what I was taught.

I will try cauls one day though.

_The set up Video:


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## cabinetman (Jul 5, 2007)

daveedoe said:


> Bill,
> 
> Thanks for the great advice. I was aware that the biscuit would not add strength to the joint, but thought it could be a good way to help ensure alignment. I've never used cauls, but those look like the way to go. Do you strongly recommend the glue joint router bit, or is it more of a nice-if-you-can kind of suggestion? If the glue will hold the jointed edges well for years to come, I'd rather not get the bit.


Using cauls is the way to go. I would not suggest using a glue joint bit for this because it's too easy to be a fraction off, and in that case, cauls wouldn't help. Biscuits don't insure alignment, and can be a delay and detriment to the glue up. Well fitted joints that are flat and square to each other (mated at 90 degrees) work best.









 







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## woodnthings (Jan 24, 2009)

*kinda nice to have...*



daveedoe said:


> Bill,
> 
> Thanks for the great advice. I was aware that the biscuit would not add strength to the joint, but thought it could be a good way to help ensure alignment. I've never used cauls, but those look like the way to go. Do you strongly recommend the glue joint router bit, or is it more of a nice-if-you-can kind of suggestion? If the glue will hold the jointed edges well for years to come, I'd rather not get the bit.


Yeah, I'd describe it that way for a one time table top build, but if you anticipate making many 3/4" glue ups, then I'd pop for the bit. I have one in a small shaper and a 1/2" shank bit for use in a router table. Here's some reviews of the router bit and there are cheaper versions than the Freud:
Amazon.com: Customer Reviews: Freud 99-031 1-1/2-Inch Reversible Glue Joint Bit


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## cabinetman (Jul 5, 2007)

Preparing wood for glue up is more of getting boards that are the same thickness, and have good mating edges. If you use a router planing jig, it will be very time consuming. You would need to get one side flat first to get the second side to finish at the same thickness. It's also likely that the finish from routing will be much more in need of dressing than if done with a planer.

I would save my money and not get the bit. With that may boards, and their lengths considered, it's likely that there won't be a harmonious fit on all the joints. To know the value and predictability of cauls, you should have them and use them properly. That will give you the alignment you need.









 







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## Steve Neul (Sep 2, 2011)

Biscuits will add strength to a joint but they're so small it doesn't add very much. There is a lot of stresses involved in a top that size that will over time try to pull the joints apart so it should have some help. I would run a spline in the joint. It doesn't have to go through the end where it shows, you could keep it about 6" from each end. If that isn't an option you might use dowels but you would have to be very accurate with them and probably get some help assembling the glue up.


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## daveedoe (Dec 1, 2012)

Fortunately for me, I have a 6 in. jointer with a pretty long table, so I think getting the perfectly square edges should be doable. I think I'll plan on going with a spline rather than the biscuits, as none of you seem to think a biscuit's going to do much good for this project. As I already have the wood, and know that some of the boards aren't quite the same exact thickness, it sounds like the the glue joint bit wouldn't be my answer.

Thanks guys! I'll post a picture of the finished product in a week or so. 

David


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## cabinetman (Jul 5, 2007)

daveedoe said:


> Fortunately for me, I have a 6 in. jointer with a pretty long table, so I think getting the perfectly square edges should be doable. I think I'll plan on going with a spline rather than the biscuits, as none of you seem to think a biscuit's going to do much good for this project. As I already have the wood, and know that some of the boards aren't quite the same exact thickness, it sounds like the the glue joint bit wouldn't be my answer.
> 
> Thanks guys! I'll post a picture of the finished product in a week or so.
> 
> David


I didn't suggest splines for this particular project, as you have many boards. The same holds true for splines as does the glue joint bit, in that if there is any slight deviation in the height alignment, cauls will not counter that and not bring the mating edges flat. 

The other point of interest is that between the setup and gluing and inserting of splines can consume enough time to put your glue into a kick off state. It's getting just enough glue in the spline grooves and on the spline, because too much will give excessive squeeze out, and not enough will be a weak joint. As for strength, biscuits do not add any strength to a joint, for axial strength. They may help in preventing the parts from pulling apart, and IMO, that's about it.

For splines to be effective, they must be a very close slip fit, and about 1/32" to 1/16" narrower than the total width of both grooves. The edges should be chamfered so very slightly, as not to scrape the sides of the groove that would create any debris when inserting. But still, the mating edges of the board (that borders the spline) have to be a very good fit. Any imperfection in the fit of the spline could impede the alignment even with using cauls.

Actually, I'm a firm believer in splines for the proper project. For others though, they can be a problem for the inexperienced woodworker. The point to all this is that for any procedure, you want the least avenues that could lead to failure. And, as a note, with any project, do a dry fit first, and have all the parts, pieces, and clamps ready at hand. You don't want to be running around the shop looking for something at the last minute.










 







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## Al B Thayer (Dec 10, 2011)

Has anyone mentioned facing the board before planing. I face every board I can. this produces a very accurate board.

Al

Friends don't let friends use stamped metal tools sold at clothing stores.


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## Daddy's Cool (Jul 12, 2010)

woodnthings said:


> To allow for movement after the top is assembled, just make elongated holes in the apron.
> Do not glue long grain stretchers across the width. If you use them drill and screw in the center, but let the ends float in elongated holes.
> Welcome. :yes:
> Take a few minutes and introduce yourself in the Introduction section of the forum.
> bill


 
Sorry to thread hijack, but I would like some clarification on the wood movement issue. Does wood tend to get longer/shorter (with the grain) or wider/skinnier (across the grain)?

What are grain stretchers?

Based on the tips above, I am guessing that the length of the table will stay the same (otherwise, how do breadboard ends work) but the width may have some fluctuations. Is this correct?


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## rayking49 (Nov 6, 2011)

Wood moves most across the grain not the length of the board. The long grain stretchers Bill is talking about is stretchers (boards being used as aprons or as braces if you will). You don't want to attach them in a way that will not let the wood float across the grain.


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## cabinetman (Jul 5, 2007)

Daddy's Cool said:


> Sorry to thread hijack, but I would like some clarification on the wood movement issue. Does wood tend to get longer/shorter (with the grain) or wider/skinnier (across the grain)?
> 
> What are grain stretchers?
> 
> Based on the tips above, I am guessing that the length of the table will stay the same (otherwise, how do breadboard ends work) but the width may have some fluctuations. Is this correct?


Sometimes parts are called different things. The principle is to allow wood to move across the grain. All the boards in the field of a top can be edge glued. What's critical is to not inhibit one or all of them from moving laterally (across the grain).

So, the trick is to use slotted holes at the apron for the ends of the boards (and at the sides) of the apron, so there will be some allowance for movement. As for the ends, a center board can be screwed down tight at its middle, and in doing that all the boards to its left and right can move in that direction. Center screwing that one board will place the top in alignment with the apron.









 







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## rayking49 (Nov 6, 2011)

CMan explains it better than I did. Sorry 4 am and on last break at work. Brain not in gear all the way. Lol


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## Retired wood prof (Apr 27, 2020)

Wood moves in two directions, expanding with increasing surrounding moisture in the radial and tangential directions. Radially cut wood referred to as quarter-sawn moves about half as much as tangential sawn wood or flatsawn. Look at the end grain if the annual rings are 80-90 degrees to the face of the board it is radially sawn. If it’s 45 degrees or less it’s flatsawn. The moisture content of the wood determines its size. . When wood is in an atmosphere where the humidity is greater than the emc of the wood then it increases, it will decrease in size if surrounding humidity is less. Use kiln dried wood and keep furniture in a controlled humidity for minimal movement. Go to the forest products laboratory to learn more about wood movement.


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