Maximum board width for glued tabletop? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 19 Old 12-16-2011, 01:20 AM Thread Starter
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Maximum board width for glued tabletop?

Hi,

Sorry if this is in the wrong section... I wasn't sure.

I have been searching around the Internet and have read some conflicting information regarding the following quesiton:

What is the maximum board width you would use for each board of a glued tabletop?

In my case, the stock I have is 6/4 red oak that has been sitting around for many years. The boards are a variety of widths, from a little less than 5" to almost 8". The tabletop will be approx 6' long and around 40-45" wide.

Some posts online have said never to use stock wider than 3" or 4", because of cupping, others have said that as long as the wood is dry and you alternate the grain from one board to the next, it shouldn't really matter how wide it is.

Thoughts? Do I need to rip the wider boards in half before gluing? Or should I be okay with whatever widths I've got?

Thanks!
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post #2 of 19 Old 12-16-2011, 03:14 AM
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Assuming they are rough sawn...?

Then you would be bound by the width of your jointer, usually 6".
In my experience, and based on the tops I've seen 6" is about maximum width anyway. The growth rings should be centered on that dimension for equalization. If the boards are already centered then ripping them in half would make them assymmetrical and may induce some warp by the process. When planing or jointing flip the boards each time to remove equal amounts from both sides. Finally if they were kiln dried rather than air dried they probably have moved all they are going to move....but you never really know until you rip them. That's just my experience. Red Oak seems to move a bit more than white in my experience also. bill

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #3 of 19 Old 12-16-2011, 05:59 AM
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In my pea brain its a function of:

wood quality and how its been sawed,taken to the second power WRT dryness,devided by the method to attain that dryness.

>The above is the numerator,the denominator below is an equation of<

Intended looks divided by where the pce is going to "live".

Those who say it cannot be done shouldn't interrupt the people doing it.
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post #4 of 19 Old 12-16-2011, 12:03 PM Thread Starter
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Actually, I don't think I need to use a jointer on the face of the boards, they are already finished S2S. I only need to joint the edges.

I believe this wood was air-dried, though I'm not sure. It was cut at a small mill about 25 years ago and has spent much of its life stacked in a guy's unheated garage, near Seattle.

I will check to see if the grain is "centered" or not when I get home later.

It sounds like most people think that 6" is a safe maximum width, though? Then I could cut some of the 8" ones in half, etc.

Thanks!
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post #5 of 19 Old 12-16-2011, 12:28 PM
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No need to rip I've used boards 23" wide 8/4 mahogany before after 10 years no cupping. It's all about moister nothing to do with grain orientation unless ur using oak or ash.
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post #6 of 19 Old 12-16-2011, 12:36 PM
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It was already mentioned but it's more a question of how stable the lumber is presently as well as how stable it's future environments will be. Unstable lumber will fail regardless of environment and stable lumber will fail under an extreme environment.

Most rely on a power jointer and hence must rip boards to that width. If the lumber is old dry stock stable stock, there will be no huge moisture change and you have the means to joint it (machine or by hand) by all means use full width boards. Align grain run-out and alternate board cup while using pieces with the flattest grain you have you should never have any problems stemming strictly from the glue up. (attaching the top to base is always a factor)

I say this because I really like using the widest boards possible for table tops. I like the look and the oooh factor. I hand joint most table top stock for this reason. I joint, let sit 24 hrs and joint again prior to glue-up and have good out comes with wide lumber.

I'm not suggesting you do this if you are inexperienced with it. Its simpler and safer to use narrower stock. I just wanted you to know there are other options.

Good luck

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post #7 of 19 Old 12-16-2011, 03:13 PM
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Agree with 3fingers and Firemedic. I have glued up 20" wide boards and have had no problems from those tables. MC is key. I also hand joint these large pieces but you can get around it. Using a sled you can flatten boards as wide as your planer.
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post #8 of 19 Old 12-16-2011, 03:38 PM Thread Starter
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3fingers: it IS oak, so then I do have to worry about grain orientation in addition to moisture, eh?

Firemedic: I don't know much about lumber stability (if you couldn't tell) but I can imagine that since it's nearly arrow-strait in all dimensions after 20+ years in an unheated/uncooled garage, it is probably pretty stable at this point?

As far as the future environment, it will be in my dining room, which experiences a rough humidity range of about 35-50% in the winter, and 45-60% in the summer. (This must be a narrower range than it experienced in the garage...)

I don't believe I need to joint the faces of the boards, as they are already finished s2s and seem quite flat. So, my 6" jointer should be able to handle the edges of any of these boards.

Regarding your comment: "Align grain run-out"
Can you describe this a bit more, as if you were talking to someone with very limited knowledge of grain characteristics?

Regarding your comment: "alternate board cup while using pieces with the flattest grain you have."
How do I know which way board cup will go? Does this just mean I need to look at the end grain and "flip" it from one piece to the next? And what is a "flat" grain?

Thanks!
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post #9 of 19 Old 12-16-2011, 04:29 PM
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The oak then needs to acclamate to where it's going to be at least two weeks! 6/4 stock should not vary so grain ordination should not matter. I use the best face, what grain will look best to the viewer. If your top was 4/4 then I would take it into consideration. Just let it sit in a heated shop for 2 weeks first. Start on the base first
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post #10 of 19 Old 12-16-2011, 05:05 PM
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I wouldn't cut up a good board just to glue it back together. I use KD lumber, and once the wood is acclimated properly, and finished, it usually sits in a fairly constant environment.








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post #11 of 19 Old 12-16-2011, 05:42 PM
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Quote:
Originally Posted by mofo83
3fingers: it IS oak, so then I do have to worry about grain orientation in addition to moisture, eh?
You must worry about that regardless of species.

Quote:
Originally Posted by mofo83
Firemedic: I don't know much about lumber stability (if you couldn't tell) but I can imagine that since it's nearly arrow-strait in all dimensions after 20+ years in an unheated/uncooled garage, it is probably pretty stable at this point?

As far as the future environment, it will be in my dining room, which experiences a rough humidity range of about 35-50% in the winter, and 45-60% in the summer. (This must be a narrower range than it experienced in the garage...)
Yes, very stable however as pointed out you should allow the lumber to acclimate you your dining room (house in general) for several weeks prior to dressing it. Some go so far as to bring pieces back in the house every eve. I'm not that anal. If your shop is climate controlled then skip that and just keep it there for a few weeks, dress it (joint & plane) and allow it to acclimate another day then check with straight edge to confirm no movement.

Quote:
Originally Posted by mofo83
I don't believe I need to joint the faces of the boards, as they are already finished s2s and seem quite flat. So, my 6" jointer should be able to handle the edges of any of these boards.
There is no such thing in nature as flat or straight as nature tends towards chaos and disorder. This is especialy true with drying lumber as the fibers all dry at different rates. They may appear flat and not be. That's ok really but it's going to mean a lot more work to flatten the glue-up with either a hand plane/jointer or belt sander.


Quote:
Originally Posted by mofo83
Regarding your comment: "Align grain run-out"
Can you describe this a bit more, as if you were talking to someone with very limited knowledge of grain characteristics?

Regarding your comment: "alternate board cup while using pieces with the flattest grain you have."
How do I know which way board cup will go? Does this just mean I need to look at the end grain and "flip" it from one piece to the next? And what is a "flat" grain?

Thanks!
Below is an exaggerated sketch explaining this. The top row illustrates alternating grain cup. The second from right (in top row) shows a highly cupped grain as the others are flatter. This is a function of how the lumber was sawn as well as where in the trunk of the tree it comes from. The tree has round growth rings so the cross section differs from board to board. Quarter sawing alleviates this to some extent however I'm pretty certain you have flat sawn lumber as is illustrated.

The bottom with the diagonal lines illustrates grain run out. It's the direction at which the grain is running where it meets the face of the board. This is most important for planing lumber, particularly oak with any knots are burls. In the illustration you would want the cutting tool to cut towards the right in order to shave the grain as opposed to tearing it up. Similar to shaving your beard, you'll notice more tug and pull when shaving in the directing opposite of how your beard lays.

As I said, grain run out is most important for planing especially by hand. So if you don't have or plane to use a hand plane don't worry too much about it. Run-out doesn't affect sanding to near the same degree.

Hopefully that answers your questions, if not ask some more. Also if this is your first rodeo be sure to ask / research attaching the top to the table prior to building to avoid problems with cracking as the table breaths. Also I should point out that a Breadboard end is not advisable for a first table... In case you were considering that.

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post #12 of 19 Old 12-16-2011, 05:58 PM Thread Starter
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Thanks again Firemedic, your explanation of the grain is very helpful.

Sounds like I just need to make sure the wood has plenty of time to acclimate in the dining room (I will probably do the glue-up in my heated basement, which is roughly the same humidity as the dining room. The sanding/finishing will probably be out in the colder garage.)

Speaking of finishing... I know I'm also supposed to finish ALL surfaces (visible or not) exactly the same to prevent warping, correct?

The (possibly dumb) question is, how much time do I have to do so? Do I have to do one coat on the top, then one coat on the bottom as soon as the top is no longer tacky? Or can I completely finish the top all at once (with multiple coats of dye, stain and poly), let dry, then do the same finish on the bottom all at once?

Thanks, sorry for all the Q's, I'm pretty green...!
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post #13 of 19 Old 12-16-2011, 05:59 PM Thread Starter
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PS: I will attach the tabletop to the apron using those z-type clips.

Also, I will not be attaching a breadboard.

This is an older post regarding this project; you were a help on that thread as well! (Some details have changed):
http://www.woodworkingtalk.com/f9/di...uestion-30550/

I have posted a new question on this thread as well regarding supports...

Last edited by mofo83; 12-16-2011 at 06:01 PM.
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post #14 of 19 Old 12-16-2011, 08:55 PM
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I realized I maybe could have been clearer when explaining run out... The bottom illustration is looking at the board from the side!

The finishing thing is not a dumb question but I'm going to explain it thoroughly because it's better to understand an answer than simply hear it:

All faces, sides, edges of wood furniture should be sealed the same. This doesn't mean they have to have equal coats of stain though, it's more about the actual sealing layer. Your poly, lacquer, varnish, shellac etc. The reason for this is so that you don't have moisture uptake or release at different rates on each side of the board causing cupping and warping. This addresses a LONG TERM concern so to answer your question there is no mad dash to cover it all. Its preventing a down the road problem for when the table is exposed to varying humidity levels.

I have an illustration depicting something similar to this by Brink if he'll let me post it!

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post #15 of 19 Old 12-16-2011, 09:27 PM
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Haha, one of my famous stick figure drawings?

Mofo, you're getting some fine advice on this thread. As with everything woodworking, everyone has their preference. Rip and flip, leave them wide, alternate grain, on and on. I can't say any one way is right, or any one way is wrong.

Any time the moisture content in a board changes, the board will move. Allowing the board to absorb/release moisture slowly will limit the movement. Soak the top face of a board with water, then dry it quickly, the board will compression warp. This is what happens to exterior wood.

Wide boards get the reputation of cupping, warping and such because it takes so long for the moisture to reach, or leave, the middle of the wood. Putting on a film finish on all sides and ends slows down the moisture transfer, allows everything to move slowly.

If the wood is acclimated to your shop, and was well dried when you got it, it should remain rather stable.
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post #16 of 19 Old 12-16-2011, 09:32 PM
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http://www.woodworkingtalk.com/f13/d...project-23676/

This thread shows some of the ways I deal with wood movement.

I made the top last February. We just had one of the wettest summers ever. I just spoke to the owner last week, there's been no problems with it.
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post #17 of 19 Old 12-16-2011, 09:43 PM
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Here is illustration Brink made to help illustrate the above compression warping. The circles represent wood cells at the end grain I presume.

Brink, I do love the trestle on the linked table!

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post #18 of 19 Old 12-18-2011, 12:15 PM
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Interesting thread.
The original question was the max width of a board used in a glue up?
You mentioned that they were old boards.
Old boards usually came from larger trees. The amount of "cupping" is related to the type of wood, the radius of the growth rings and the change in humidity that the final board will experience.
As mentioned you should try to be sure the boards are as close to the final moisture content as possible. Usually we expect 6-8% at most. The wood will still get changes in humidity and therefore dimension change including cupping unless you live in a very stable usually arid place. No finish will change this other than the rate of change.
Older board with large radius arcs will be less subject to cupping than most of the timber that we get now (with a few pleasant exceptions). Therefore they can and usually are left at their given width. Sometime a wide board with a significant cup over its width is cut more narrow before jointing to avoid loss of thickness. The board once to thickness, can be put back together with good grain match. That seems the only reason to cut a wide board as the amount of cupping will be the same wether it's made narrow then glued up.
The question of growth rings being put together the same or opposite ways has often been debated. Keeping them the same way allows the fastening system to hold minor cupping flat. Severe cupping may overwhelm the screws but if obviously very bad boards are avoided it works well.
The system of alternating the growth ring curves has been suggested here and is preferred by some. You may have a wavy tabletop.
The looks of the board with grain patterns that have harmony is probably the best way to go. Avoid anyboard with small radii growth rings as they are too close to the tree centre and using them is asking for trouble.
The run out question came up in the discussion and the drawing shows the issue well. When you are jointing the boards, you will use or find the best directions to plane that avoids tear out. If you put an arrow on any board requiring special care, then you can orient the boards in the same direction for glue up to minimise tearout when the glued up board is planed.
Enjoy the old wide boards they are a treasure.
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post #19 of 19 Old 12-28-2011, 01:21 AM Thread Starter
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Just a little update:

I figured I'd start small so I'm making a bench seat first, using the same construction techniques I will use for the dining table.

I ended up rippind the boards to less than 6", because you were right, they looked flat but still needed a little help from the jointer. (I also did my first jointer blade change... fun ) I can use the leftover 2" pieces for the leg glue-ups. The bench-top glue-up seems to have gone fine... surprisingly! There are only a few spots where I need to sand down the height difference between two boards.

I am thining I should be able to get the bench close to finished within a week or two.

Thanks again for the help!
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