zole2112

Bench Leg Attachment Question

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A friend made a live wood bench for me for my wife Christmas. He lives in a different state and shipped me the bench with the top and the legs in separate pieces. The legs are a single piece of pecan per side with a dimension of appx 16"x12". He has 2 dowels inserted into each leg for attaching to the bench top as well as holes for 3 screws. I was going to glue and screw the legs on but when I attach them the legs do not sit fully against the bench top along the entire length of the leg, a gap exists in the center area, the bench top is not completely flat. I'm not sure what to do with it, I was thinking of sanding the ends of the legs to get them to fit tight. In addition, there is no other bracing and I'm worried that the legs will come loose over time. I can add pictures when I get home, at work now. I'm hoping to get some suggestions from some experienced woodworkers on my best path forward. I want a stable bench that will last for a long time.

thank you!

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Sounds like the bench slab has cupped due to moisture changes within the wood, either from humidity changes, or because the wood was not fully dried when the bench was built. Any solution should probably wait until closer to Christmas so the wood has more time to acclimate. That wood will probably move more between now & then.

If you post some pics, we can better suggest a fix. Have you talked to the guy that built it? He might be in the best position to offer a solution.

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Here are pictures of the bench. I haven't contacted him yet. Good idea to wait until closer to Christmas to address it, I didn't even think about that. Yes it does look like it cupped.

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From what I can see it appears the problem was caused when the builder finished only one side of the board sealing one side and allowing moisture and air on the other is not a good idea. To fix it correctly it will need to be re-flattened and then sealed on all 6 sides. 

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Easiest fix may be to just get a cabinet shop to run the underside of the slab over a jointer to flatten it. Then give it a couple of coats of finish.

Is it just dowels & glue that will be holding the legs on? If so there will be a danger of it racking & collapsing when someone sits on it not too gently. Problem is that glue on the end grain will have no strength & those dowels are pretty short & only hold well where they are in contact with the long grain inside the holes. A bunch of floating tenons (Dominos) running crossways along the top of the leg would be a LOT stronger.

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2 minutes ago, zole2112 said:

Thank you guys. I'll contact a shop tomorrow to see if i can get it planed. I was worried about it collapsing too, I'll work on that as well.

Router sled would also work for flattening.

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2 hours ago, pkinneb said:

From what I can see it appears the problem was caused when the builder finished only one side of the board sealing one side and allowing moisture and air on the other is not a good idea. To fix it correctly it will need to be re-flattened and then sealed on all 6 sides. 

I’ve read articles that dispute this notion. Here is one from Bob Flexner.

https://www.woodshopnews.com/columns-blogs/finishing-both-sides-is-warped-thinking

I think the movement likely occurred from the change in climate between the two states when it was shipped.

For me, I’d first test it on hard tile or concrete floor. Can it be bent flat from a modest amount of force? If so, I’d get some cheep clamps from harbor freight and clamp it up, with the legs in place, no glue. Let it rest a couple weeks. Hopefully it relaxes into the flat shape we like as the moisture content reaches equilibrium. If it remains persistently curved, others are correct that reflattening is the next step. 

You can reinforce the leg connection with steel corner shelf angles. Something like this, painted flat black and located on the center, interior of each shelf would hardly be noticed.

https://www.amazon.com/LuckIn-Bracket-Furniture-Shelves-Stainless/dp/B07DNPP1CX/ref=sr_1_7?ie=UTF8&qid=1544155244&sr=8-7&keywords=triangle+corner+bracket

You could reinforce with dominos, but if you had that option, you probably wouldn’t be consulting here to begin with. 

You could do something with wood , finding material to match will be your biggest challenge

 

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I just read up on router sleds, that's an awesome idea. I will first try to see if I can bend it flat and if so I will clamp it and let it rest for a couple of weeks to see if it does relax. It did ship from Georgia to Wisconsin, since it's winter here now we have very low humidity compared to Georgia.

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5 hours ago, Isaac said:

I’ve read articles that dispute this notion. Here is one from Bob Flexner.

https://www.woodshopnews.com/columns-blogs/finishing-both-sides-is-warped-thinking

Interesting read, thanks for sharing!

+1 for adding some sort of corner brace to prevent racking if it will see regular use. If it will just be decorative and only rarely sat on, it may be fine to leave it as-is.

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Did everyone miss the pocket screws attaching the legs to the bench? Never used the things but don't they do a decent job of holding things together?

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38 minutes ago, Chestnut said:

Did everyone miss the pocket screws attaching the legs to the bench? Never used the things but don't they do a decent job of holding things together?

I was concerned that the 3 pocket screws would not provide enough strength so I think I will definitely add some brackets as well.

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10 hours ago, Isaac said:

I’ve read articles that dispute this notion. Here is one from Bob Flexner.

https://www.woodshopnews.com/columns-blogs/finishing-both-sides-is-warped-thinking

I think the movement likely occurred from the change in climate between the two states when it was shipped.

I respectfully disagree. I don't doubt that change in climate could affect it as well but in my experience sealing one side of a board causes unwanted results.

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1 hour ago, Chestnut said:

Did everyone miss the pocket screws attaching the legs to the bench? Never used the things but don't they do a decent job of holding things together?

I don't think they will provide the type of resistance we are getting at, which is bending/racking. Frankly, even with a bunch of short dominoes, there would still be some risk of breakout if it was stressed. Think of a rowdy, big enough to know better, kid landing on the thing with as much horizontal force as downward force. Sounds insane, but I've seen teenagers regularly dive, flop or otherwise throw themselves onto couches, for example. My almost nine year just insists on jumping on his bed from time to time, no matter how many times I've asked him not to! :). With that type of loading, the pocket screws will tear out. Ideally you'd have a stretcher between the legs. My metal bracket idea is just a simpler fix that wouldn't be too obtuse and is feasible for the average homeowner. 

20 minutes ago, pkinneb said:

I respectfully disagree. I don't doubt that change in climate could affect it as well but in my experience sealing one side of a board causes unwanted results.

I don't really have a strong opinion on it, haven't had an issue that I'd attribute to this. Most of my projects have larger issues that I can more directly attribute to operator error! :blink:

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9 minutes ago, Isaac said:

I don't they will provide the type of resistance we are getting at, which is bending/racking. Frankly, even with a bunch of short dominoes, there would still be some risk of break out if it was stressed. Think of a rowdy, big enough to know better, kid landing on the thing with as much horizontal force as downward force. Sounds insane, but I've seen teenagers regularly dive, flop or otherwise throw themselves onto couches, for example. My almost nine year just insists on jumping on his bed from time to time, no matter how many times I've asked him not to! :). With that type of loading, the pocket screws will tear out. Ideally you'd have a stretcher between the legs. My metal bracket idea is just a simpler fix that wouldn't be too obtuse and is feasible for the average homeowner. 

I don't really have a strong opinion on it, haven't had an issue that I'd attribute to this. Most of my projects have larger issues that I can more directly attribute to operator error! :blink:

Interesting that you mention a stretcher. I was searching online for a piece of pecan that I could use as a stretcher but I was not successful so I started looking for different solutions which led me to this forum, which is awesome!

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2 minutes ago, zole2112 said:

Interesting that you mention a stretcher. I was searching online for a piece of pecan that I could use as a stretcher but I was not successful so I started looking for different solutions which led me to this forum, which is awesome!

Where are you located? google "hardwood lumber" and see who can you find around you. Many places have websites that list what they carry. Obviously, you will not find this at Homedepot...

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21 minutes ago, Isaac said:

Think of a rowdy, big enough to know better, kid landing on the thing with as much horizontal force as downward force. Sounds insane, but I've seen teenagers regularly dive, flop or otherwise throw themselves onto couches, for example. My almost nine year just insists on jumping on his bed from time to time, no matter how many times I've asked him not to! :). With that type of loading, the pocket screws will tear out. Ideally you'd have a stretcher between the legs. My metal bracket idea is just a simpler fix that wouldn't be too obtuse and is feasible for the average homeowner. 

Or 30 year old guy that refuses to grow up and still does the above mentioned stuff... At least now if i break I get to fix it without the lecture. I guess i was unsure about the whole pocket hole strength. I thought they'd be decently strong beings they are basically a screw into a good hardwood.

I should hire one of these teenagers some day. It'd be nice to have a test engineer to do destructive testing of designs that i have in mind.

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1 minute ago, Chestnut said:

Or 30 year old guy that refuses to grow up and still does the above mentioned stuff... At least now if i break I get to fix it without the lecture. I guess i was unsure about the whole pocket hole strength. I thought they'd be decently strong beings they are basically a screw into a good hardwood.

I should hire one of these teenagers some day. It'd be nice to have a test engineer to do destructive testing of designs that i have in mind.

The problem isn't the fastener, it is the location. If we were just talking about a straight pull out test, I'd be with you. But we are talking about a bending moment. The fastener will be dead center on that leg, so it will have a resisting arm of about 1/2". Add a 6" bracket like I showed above and you've increased the bending resistance roughly 12x for the same strength screw. 

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12 minutes ago, Isaac said:

The problem isn't the fastener, it is the location. If we were just talking about a straight pull out test, I'd be with you. But we are talking about a bending moment. The fastener will be dead center on that leg, so it will have a resisting arm of about 1/2". Add a 6" bracket like I showed above and you've increased the bending resistance roughly 12x for the same strength screw. 

Do the hardwood dowels count for little in terms of moment reduction? I didn't really see the screws as resisting the moment but more so as stopping the joint from separating. If the corner of the leg acts as the fulcrum and the dowel resists the moment the screw is left to take the tension forces trying to separate the joint?

Sorry this is slightly off topic but the only structures stuff i know is what i remember from school and that was concrete and steel design i never took timber design. REALLY wish i had though.

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I agree with Isaac on the pocket screws not being enough for this application. They do a pretty good job at holding things together (better than many people give them credit for), but this isn't their ideal application.

It's hard to tell from the angle of the picture, but it looks like they were drilled at the ~3/4" setting, so it's a shorter screw and there isn't as much material between the head of the screw and top of the leg as could be used.

It would feel solid as is and may continue to feel solid for a few years, or it may not.

 

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I'm located in Appleton, WI. I have 2 grandsons, 3 and 4 and the 3 year old is already a huge beast lol, he will not be gentle and I know my wife will want to use the bench at the dining table.

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Are the dowels glued into the legs or do they just float in there?

Do the dowels fit tightly into the seat, or is there a bit of wiggle room?

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You are in a great place for inexpensive hardwoods. I find well priced stuff around green bay all the time. Might have to do some searching but you will find stuff.

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The dowels are tight in the legs and fit tight into the bench top. they are glued into the legs currently.  When I originally searched for a piece of wood for a stretcher I searched only for pecan, any suggestions on a wood that would compliment the pecan that would be appropriate for the stretcher? Also what is the best way to attach the stretcher?

So my plan now is:

1) check to see if I can flatten and clamp it, the initial check i did looked like I couldn't

2) wait a couple of weeks for it to acclimate to my climate

3) Use a router sled to flatten the bottom if necessary - this looks interesting to me

4) attach the legs with glue, the dowels, the pocket screws and a stretcher board for strength against my grandsons

Thank you guys for all of your comments, it's been really helpful!

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