Newbie building a desk. - Woodworking Talk - Woodworkers Forum
 
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post #1 of 12 Old 03-23-2018, 10:14 PM Thread Starter
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Newbie building a desk.

I'm fairly comfortable with the tools involved, but most of my experience is in building houses, so I don't have a ton of experience with the finer side of wood working. I have a desk I want to build, and I'm looking for some tips.

I would like the desktop to be multiple different hardwoods, laid out like a hardwood floor, kind of like in this cutting board: https://www.pinterest.com/pin/120541727498976505/
My original thought was to cut a tongue or groove into all four sides of each piece, and then lay them just like a hardwood floor on a piece of 3/4" cabinet grade plywood. Then I started wondering if that was just a whole lot of work with no real benefit, and thought I could probably cut them all more like 1/4"-3/8" thick instead of 3/4" and just glue them down with butt joints. Saves on labor, weight, materials, but I don't know if it would impact the quality of the final product.

Is there a reason I would regret the second method, pros and cons to each way? Maybe a third recommendation?
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post #2 of 12 Old 03-23-2018, 10:19 PM
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Your plan to glue them to plywood or MDF will work fine as long as you run all your grain in the same direction. It can be a very colorful desk top.
You will most likely have to use a hand plane some.
Try to avoid a belt sander.
For a perfectly flat top, itís best to block sand by hand.

If you don't have time to do it right the first time, when will you have time to do it over?
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post #3 of 12 Old 03-23-2018, 10:22 PM Thread Starter
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Different grain direction= different growth and shrinkage with the seasons= weird gaps and my desktop basically tearing itself apart?
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post #4 of 12 Old 03-23-2018, 10:36 PM
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In the picture you show a cutting board made of many strips of different types/colors of wood. But all the grain runs the same direction. This is important.

If you don't have time to do it right the first time, when will you have time to do it over?
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post #5 of 12 Old 03-23-2018, 11:26 PM
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I've built a few tables in a similar style. It's just glue: no biscuits, dowels, grooves, nothing like that, and it's plenty strong. It's secured to the apron with Rockler's table top clips to allow for wood movement. (Also, since my planer can handle up to 13 inches, I actually assembled it in three sections and ran each section through the planer to the same thickness, then glued them together: Means a LOT less leveling at the joints).

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Your plan to glue them to plywood or MDF will work fine as long as you run all your grain in the same direction. It can be a very colorful desk top.
You will most likely have to use a hand plane some.
Try to avoid a belt sander.
For a perfectly flat top, itís best to block sand by hand.
I'm a little confused by Toolman50's response. It was my understanding that gluing wood (which will expand and contract with humidity) to MDF or plywood (which will NOT expand and contract) is a recipe for disaster: I would imagine the wood would buckle when expanding and break apart at the joints when contracting. But then, he has 3600 posts and I've got like 100, so he probably knows a lot more than I do.
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post #6 of 12 Old 03-24-2018, 06:37 AM
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Quote:
Originally Posted by mackman View Post
I'm a little confused by Toolman50's response. It was my understanding that gluing wood (which will expand and contract with humidity) to MDF or plywood (which will NOT expand and contract) is a recipe for disaster: I would imagine the wood would buckle when expanding and break apart at the joints when contracting. But then, he has 3600 posts and I've got like 100, so he probably knows a lot more than I do.

Mackman is correct. Gluing the planks to the top of plywood/mdf creates an unbalanced panel which WILL warp. Whatever you do to the top you must do to the bottom. If you add 3/8" thick planks to the top, you'll need to add 3/8 planks to the bottom.

If your material is thick enough (3/4"+), you could TnG it and glue it up without a substrate. It would be plenty strong.
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post #7 of 12 Old 03-24-2018, 09:32 AM
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Originally Posted by Callipygous View Post
I'm fairly comfortable with the tools involved, but most of my experience is in building houses, so I don't have a ton of experience with the finer side of wood working. I have a desk I want to build, and I'm looking for some tips.

I would like the desktop to be multiple different hardwoods, laid out like a hardwood floor, kind of like in this cutting board: https://www.pinterest.com/pin/120541727498976505/
My original thought was to cut a tongue or groove into all four sides of each piece, and then lay them just like a hardwood floor on a piece of 3/4" cabinet grade plywood. Then I started wondering if that was just a whole lot of work with no real benefit, and thought I could probably cut them all more like 1/4"-3/8" thick instead of 3/4" and just glue them down with butt joints. Saves on labor, weight, materials, but I don't know if it would impact the quality of the final product.

Is there a reason I would regret the second method, pros and cons to each way? Maybe a third recommendation?
There are a few designs on that link because of wood movement issues I would avoid and the end grain cutting boards would need additional support for a desk top. Most of which you could just glue up without the need for tongue and groove and just use it for the top. If you have a jointer and make your glue joints fit well to where the wood pulls together without forcing it, it's true what the glue manufacturers say, the joints are stronger than the wood itself. Besides if you make tongue and groove this would show up on the end of the top which wouldn't look nice.

As far as laying the top on plywood that would depend on which design you used and how it was mounted. Most of those would need no additional support. You would have to be very careful how it would be mounted to the plywood. You couldn't glue it on. If you used screws the holes would have to be elongated to allow the wood to shrink. The solid wood will shrink a great deal more than the plywood will. Also since it should not be glued the underside of the top should be finished before using or mounting to plywood. It's important on a large piece of wood to seal both sides to prevent warpage. A board will cup when the moisture contents differs from one side to another.
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post #8 of 12 Old 03-25-2018, 12:47 AM Thread Starter
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So Steve, from what your saying it sounds like option 2 is out. I was talking about gluing 1/4" x ~1 1/2" x 8-30" pieces directly onto plywood, and it seems like multiple people are telling me that will result in problems due to the top moving, while the plywood substrate remains stable.

My intention with my first option was also to glue it to the plywood, but I guess that's out too. So how about glue the whole top together, give it a bullnose at the edge, fully finished etc, and then should I still fasten it to a piece of plywood to keep the whole thing flat and stable, or is that not necessary? Screws up through the plywood, with holes in plywood elongated across the direction of the grain?

Thanks for all the replies!
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post #9 of 12 Old 03-25-2018, 09:19 AM
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Originally Posted by Callipygous View Post
So Steve, from what your saying it sounds like option 2 is out. I was talking about gluing 1/4" x ~1 1/2" x 8-30" pieces directly onto plywood, and it seems like multiple people are telling me that will result in problems due to the top moving, while the plywood substrate remains stable.

My intention with my first option was also to glue it to the plywood, but I guess that's out too. So how about glue the whole top together, give it a bullnose at the edge, fully finished etc, and then should I still fasten it to a piece of plywood to keep the whole thing flat and stable, or is that not necessary? Screws up through the plywood, with holes in plywood elongated across the direction of the grain?

Thanks for all the replies!
There are so many different styles of cutting boards on that link it's difficult to understand which one you have in mind. If the grain direction runs horizontal you can glue up wood in different widths and lengths and it will do fine. As long as you stagger the joints you can butt some of the pieces end to end to gain length also. Once glued together it will function as though it was a single piece of wood.

Gluing the top to plywood is unnecessary and undesirable. It can easily instigate a cup warp where the top wouldn't otherwise. The solid wood top even if you finish it thoroughly is going to expand a little in damp weather and shrink in dry weather and overall over time shrink in width as it ages. Plywood since it has grain running in alternate directions is prevented from as much shrinkage so if you have it laminated to one side of the top when the other side swells up it will bow up. Then if it shrinks it will cup in the middle. It's important that both sides of the top move in the same direction.
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post #10 of 12 Old 03-25-2018, 01:34 PM Thread Starter
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There are so many different styles of cutting boards on that link it's difficult to understand which one you have in mind.
I don't intend to emulate any particular cutting board, it was just meant as a visual aid to avoid having to describe the general idea I was going for. It seems like on this forum people are pretty familiar with the idea, so it probably wasn't necessary.

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Gluing the top to plywood is unnecessary and undesirable. It can easily instigate a cup warp where the top wouldn't otherwise. The solid wood top even if you finish it thoroughly is going to expand a little in damp weather and shrink in dry weather and overall over time shrink in width as it ages. Plywood since it has grain running in alternate directions is prevented from as much shrinkage so if you have it laminated to one side of the top when the other side swells up it will bow up. Then if it shrinks it will cup in the middle. It's important that both sides of the top move in the same direction.
I get that now, no gluing hardwood to plywood. What I am trying to ask is whether there is any benefit to fastening the hardwood top onto plywood (with screws or some other method that allows movement) to keep it flat. My impression is that if I glue a bunch of hardwood pieces together with the grain running the same direction it wont really resist warping as the seasons change. So how do I make sure it stays flat? Normally if you build a big flat surface like this you would give it an apron, or breadboard ends or something to keep it from cupping, right?
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post #11 of 12 Old 03-25-2018, 01:52 PM
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I don't intend to emulate any particular cutting board, it was just meant as a visual aid to avoid having to describe the general idea I was going for. It seems like on this forum people are pretty familiar with the idea, so it probably wasn't necessary.



I get that now, no gluing hardwood to plywood. What I am trying to ask is whether there is any benefit to fastening the hardwood top onto plywood (with screws or some other method that allows movement) to keep it flat. My impression is that if I glue a bunch of hardwood pieces together with the grain running the same direction it wont really resist warping as the seasons change. So how do I make sure it stays flat? Normally if you build a big flat surface like this you would give it an apron, or breadboard ends or something to keep it from cupping, right?
You really shouldn't worry about the top warping. Generally this only happens if the wood was still green when it was built or the underside wasn't sealed. The majority of the time there isn't the slightest issue. You might just mount the top to the desk like you would with the Rockler table top clips. The clips will hold the top flat while allowing for wood movement.
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post #12 of 12 Old 03-25-2018, 03:11 PM
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Originally Posted by Callipygous View Post
I'm fairly comfortable with the tools involved, but most of my experience is in building houses, so I don't have a ton of experience with the finer side of wood working. I have a desk I want to build, and I'm looking for some tips.

I would like the desktop to be multiple different hardwoods, laid out like a hardwood floor, kind of like in this cutting board: https://www.pinterest.com/pin/120541727498976505/
My original thought was to cut a tongue or groove into all four sides of each piece, and then lay them just like a hardwood floor on a piece of 3/4" cabinet grade plywood. Then I started wondering if that was just a whole lot of work with no real benefit, and thought I could probably cut them all more like 1/4"-3/8" thick instead of 3/4" and just glue them down with butt joints. Saves on labor, weight, materials, but I don't know if it would impact the quality of the final product.

Is there a reason I would regret the second method, pros and cons to each way? Maybe a third recommendation?
Decades ago, I built a coffee table in the manner you suggested, but I used particle board instead of plywood. It was an "inlay" pattern made of relatively large oak squares and rectangles, with walnut strips in between. Everything was 3/4 inch thick, making the table top 1-1/2 inches thick in total from the particle board and the wood pieces on top.

There were many places were adjacent pieces were crossgrain to each other. Everything was glued down to the particle board, and glued on the edges between the pieces. I used screws from behind to clamp the oak pieces to the particle board, and pipe clamps to hold the top pieces together. Between the glue and the screws, nothing was gonna move. (Yeah, right.)

Over the years, none of the pieces cracked, but many gaps appeared between the pieces. I would guess that they were 1/16 inch wide, with variations. The gaps didn't bother me much, but they bothered my woodworking expert roommate a lot.

I was young and dumb then. Now I am older and still dumb. I made the same mistake when I glued the breadboard ends on a cutting board last September. I hope it lasts, but I told the gift recipients that it might crack, and I would make them a correct one if it did.

Bottom line: The "screw it to the plywood" idea is not a good one. The wood will crack or split or gaps will appear. My previous work is a testament to that.
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