Need advice on a bench (design and joints) - Woodworking Talk - Woodworkers Forum
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post #1 of 12 Old 10-28-2017, 12:20 AM Thread Starter
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Need advice on a bench (design and joints)

I'm about to start on a pair of long benches to go along with a table I'm building.

Here's the best design I was able to come up with so far (sorry for the poor quality photo of my computer screen). The top is an 11.5" wide solid slab almost two inches thick and six feet long. The legs and diagonal braces are true 2x material.

First, I'm open to any critique of the design itself. The intention is to coordinate with the pictured table, and also to "knock down" for transport if possible.

Second, any suggestions on how to attach diagonal braces like these? I could just use those metal corner reinforcers made from angle iron, but that would detract from the otherwise 100% wood construction (excepting screws used to hold the table and bench slabs to their respective legs).

Thanks for any feedback!
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post #2 of 12 Old 10-28-2017, 05:51 AM
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Mortise and tenon?
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post #3 of 12 Old 10-28-2017, 07:12 AM
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Your design may need a board running across the bottom from one leg to the other like the table does. It doesn't have to be very big. It's just over time the seat may sag and without some kind of cross brace would make the legs bow outwards. The cross braces I would just glue it and put a screw up into the seat. You could countersink the hole and put in a hole plug to hide the screw.
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post #4 of 12 Old 10-28-2017, 10:35 AM Thread Starter
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Originally Posted by ducbsa View Post
Mortise and tenon?
That's the first thing that came to mind, however I don't know that I could execute it accurately (in terms of the mortise and tendon having minimal gaps for a good glue up. Maybe I could supplement the MT with some dowels or something though.
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post #5 of 12 Old 10-28-2017, 10:42 AM Thread Starter
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Originally Posted by Steve Neul View Post
Your design may need a board running across the bottom from one leg to the other like the table does. It doesn't have to be very big. It's just over time the seat may sag and without some kind of cross brace would make the legs bow outwards. The cross braces I would just glue it and put a screw up into the seat. You could countersink the hole and put in a hole plug to hide the screw.
Steve, I think it's time for me to write you a check, I'm pretty sure you've replied to almost all of my threads!

I was also thinking about that issue of the legs bowing out. Will need to do a mockup to see if the lower tie would interfere with people's feet, like if they want to tuck their legs under the bench. I guess I could also just add a third leg and forego any kind of horizontal bracing, which would simplify things.

Soubds like I'll need to rethink the design somewhat, so I might post a "version 2" later today and seek more feedback.
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post #6 of 12 Old 10-28-2017, 11:10 AM
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Desertsp,
I suggest you drop the idea of the diagonal bracing and go with a horizontal brace like on the table you show. The bench would better match the table and the horizontal would be much easier for you to make. I have a similar harvest table in my photos but no bench. My table is assembled without screws so it can be disassembled by removing two keys which hold the horizontal brace to the two trestles.

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 #7 of 12 Old 10-28-2017, 12:16 PM Thread Starter
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Desertsp,
I suggest you drop the idea of the diagonal bracing and go with a horizontal brace like on the table you show. The bench would better match the table and the horizontal would be much easier for you to make. I have a similar harvest table in my photos but no bench. My table is assembled without screws so it can be disassembled by removing two keys which hold the horizontal brace to the two trestles.
Your keyed design is what I'm planning on doing for the table, so it would indeed be a better match on the benches as well. I haven't started that part of the table yet and thought it might turn out to be difficult, hence trying to find an alternative for the benches. Maybe I'll just go forth with the table using the "keyed" joints, and by the time that's finished I'll be able to do it 4x more times for the benches. No better way to learn than do the same thing 6 times in a row lol. I'll be using a drillpress and chisel to cut the mortises so I should be able to get them fairly accurate but not perfect.

So in your experience, is a keyed design like that strong enough by itself to resist torqueing? I'm picturing a scenario where the table (or benches) are shoved hard from one end. That's where I thought the diagonal member would come into play, but from what you're suggesting it may be overkill.

Nice examples of your work, btw!

http://www.woodworkingtalk.com/membe...en-apart-move/
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post #8 of 12 Old 10-28-2017, 03:12 PM
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Originally Posted by desertsp View Post
Steve, I think it's time for me to write you a check, I'm pretty sure you've replied to almost all of my threads!

I was also thinking about that issue of the legs bowing out. Will need to do a mockup to see if the lower tie would interfere with people's feet, like if they want to tuck their legs under the bench. I guess I could also just add a third leg and forego any kind of horizontal bracing, which would simplify things.

Soubds like I'll need to rethink the design somewhat, so I might post a "version 2" later today and seek more feedback.
As thick as the seat is it would take quite a while before it would sag. It's just that the more the seat would sag the more the bottom of the legs would go outward. The cross piece wouldn't have to be much, just anything that would tie one leg with the other. It could be a 1x2 laying flat on the floor.
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post #9 of 12 Old 10-28-2017, 05:56 PM
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Quote:
Originally Posted by desertsp View Post
Your keyed design is what I'm planning on doing for the table, so it would indeed be a better match on the benches as well. I haven't started that part of the table yet and thought it might turn out to be difficult, hence trying to find an alternative for the benches. Maybe I'll just go forth with the table using the "keyed" joints, and by the time that's finished I'll be able to do it 4x more times for the benches. No better way to learn than do the same thing 6 times in a row lol. I'll be using a drillpress and chisel to cut the mortises so I should be able to get them fairly accurate but not perfect.

So in your experience, is a keyed design like that strong enough by itself to resist torqueing? I'm picturing a scenario where the table (or benches) are shoved hard from one end. That's where I thought the diagonal member would come into play, but from what you're suggesting it may be overkill.

Nice examples of your work, btw!


http://www.woodworkingtalk.com/membe...en-apart-move/
You know how it is after you complete a project, you see things that you would add, eliminate or change. We like the table a lot. Its 1 3/4 Red Oak, very solid and heavy. If I were to make it over I would not route grooves in the top (this was a look we liked when it was being made), I would drop the height of the horizontal brace 6-8 (I wanted it centered when I built it) but a 8 drop would add more resistance to being racked when shoved on the end. If you shove my table now from the end you get a 3/4 -1 movement at the top before the bottom starts to slide across the floor. No big deal but still...
The verticals of the trestles are pinned to the table top with long small dowels which can be punched out to disassemble. It will all come apart into 4 pieces ( top, brace, and 2 trestles) plus the two keys.
This table is used daily and will last several generations unless thrown out.

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 #10 of 12 Old 10-28-2017, 09:20 PM
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leg bracing on tables and benches ...

This can be explained by taking a 3 x 5 card and bending the ends at 90 degrees about 1" in. Kinda looks like a "C"clamp, but it has no strength against racking on the long dimension. A simple fix would be to add a stiffener down the center under the top and attached to the ends. so now we have "planes" of material in 3 axis, X,Y, and Z.

Depending on the strength of the attachments from one plane to the other, you mockup will be relatively stable relative to the thickness of the 3 x 5 card. Within each plane there are hidden diagonal or triangles and you could just as well use toothpicks to illustrate them and how they strengthen the structure.

Depending on the design of the structure you can use the joinery, rather than separate attachments, like metal braces or screws. Mortises and tenons with shoulders and wedges can make a very stable structure, without screws.

A bench will have greater forces applied to it laterally than a table because there may be more than one person sitting on it and moving in opposite or parallel directions with greater force than would normally be on a table.

Then there is the "design" part of the design... HUH?
How does it look? All the diagonal braces get real busy for me and I don't care for the look, even though it may be structurally sound. The simpler the better is my design vocabulary, less is more.

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 #11 of 12 Old 10-29-2017, 01:12 AM
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I agree with dropping the angles and adding the cross bar to match table.

Span......2" thick and 11.5" wide.....solid wood...sag....their out of their mind. Let's do the math...ACCORDING to pic and guesstimating the setbacks and trestle size.... The trestle is inset 6-9" from each end PLUS the trestle upright width 4-5" equals approx 10-14" inset or a true approx 48" span......IF a almost 2" x 11.5" solid wood bench can't span 48" then there's A LOT of old furniture that's survived improperly with NO SAG. I have 3 heavily used antique benches with 48-60 " spans (at 1 1/2" thick) with splayed (angled) legs with no sags.

JUST SAYING!!!......HISTORY tells it's own story!!!

Have a Blessed and Prosperous day in Jesus's Awesome Love, Tim
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post #12 of 12 Old 10-29-2017, 11:04 AM Thread Starter
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Thanks everyone for your feedback and advice. I'm really glad I asked!

The plan is now to simply use a single horizontal member connected into the legs using mortise and tennon. Probably glued, unless I find that it's not difficult to implement the removable/keyed mortises on the table. There's less of a need for the benches to knockdown (the table HAS to, it won't even fit through the hallway otherwise).

The vertical members in the legs are 3.5 inches thick, so hopefully even with my beginner level MT accuracy there will be enough surface area in the joint to resist racking forces. I guess I can add diagonal members afterwards, if needed.
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