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Cast Iron Table legs to Slab wood Table top

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Forum topic by Slade posted 11-15-2018 10:16 AM 1480 views 0 times favorited 24 replies Add to Favorites Watch
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Slade

7 posts in 28 days


11-15-2018 10:16 AM

Topic tags/keywords: slab table legs

My first time posting, but I’ve always found helpful advice to questions when reading others posts. Take it easy on my drawing skills, as i’m just learning sketchup. So I’m building a slab table. Its a large slab of Sycamore. 30-35”W x 100.5”L x 2.1/4”D. I did a epoxy finish on the table and i think it look pretty slick. My concerns are with the legs. I have some cast iron wishbone legs that i’d like to use for this beast. The top plate of the Legs are 12” x 5 1/4” with four holes in them. Do you think this is a large enough plate to simply recess into the bottom of the wood and i’d be safe from racking? I’ve attached a ‘default’ picture of what this would look like.

Since I’m not sure if that would be safe from racking, i was toying with the idea of making a larger top plate that i would weld four bolt shafts at the same locations as the ‘default’ top plate. This way i could attach the legs to the larger top plate. I would also epoxy the ‘new’ top plate into a recess thats routed out and then screw it in to the table top. I think this would serve two purposes. one is to make it more sturdy and two would make it easily movable in the future as i could just remove the four bolts and the legs will come off.

If thats still not enough to prevent racking an additional thought i had would be to run a horizontal 1/4”x4” plate connecting the two new top plates and recess that as well.

Any advice would be appreciated.

Slade

-- Slade


24 replies so far

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bilyo

419 posts in 1302 days


#1 posted 11-15-2018 03:48 PM

I think your Sketchup drawing is just fine. Better than I could do. My gut feeling is that your top plate connection to the table will be OK. My gut also makes me more concerned about the top plate connection with the vertical leg member. I wonder if this and the vertical piece will be strong enough and stiff enough to resist flexing, table wobble, and maybe failure. At the least, I wonder if some gussets at that top connection and a stretcher between the two legs would be advised. You might find someone who can do a structural analysis based on the strength of the steel (did you mean cast iron or wrought iron?) and the welds.

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jbay

2873 posts in 1099 days


#2 posted 11-15-2018 04:01 PM

The way it is may be OK but not great. Attached with some 1/4” or 5/16” lag bolts.

If you could weld or bolt a separate plate turned sideways, it would be more help with the racking.

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Manitario

2681 posts in 3083 days


#3 posted 11-15-2018 04:32 PM

Adding more bolts or larger attachment plates probably won’t help with the inevitable racking the table will experience. The wood is going to fail long before the hardware will, and even with larger attachment points, you’re expecting them to deal with a large amount of force. This would be fine if it was a coffee table but I’m not sure how it’ll stand up to 20y of big uncle Jim slamming his gut into it at every family dinner.

-- Sometimes the creative process requires foul language. -- Charles Neil

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Slade

7 posts in 28 days


#4 posted 11-15-2018 04:39 PM

Thanks guys. The legs are cast iron depicted below. Thats why I’m going the bolting on route, as i dont think welding to cast iron would work out.

I was caught up on extending the top plate i didnt think to run it sideways instead of the same direction it was running.

So JBay, if i went your route, would i need to mess with running a piece between the two plates, or do you think just the bigger plates turned sideways would suffice?

Manitario, whats the best option to reduce the racking so it would last with big uncle jims gut upsetting my bulid? lol. Would welding two 4” wide 1/4 thick plates on each end of the plates fix this? That way the legs are reinforced by the these two cross bars, that i could also recess and bolt into the tabletop.

Maybe something like this?

Man its so nice to get some feedback, i appreciate it. This stuff keeps me up at night!

-- Slade

View Phil32's profile

Phil32

266 posts in 103 days


#5 posted 11-15-2018 06:25 PM

One question that has not been raised is the actual weight of the slab top. The 2-1/4” thick slabs of sycamore that I’ve dealt with are fairly heavy, depending on the moisture content.

-- Phil Allin - Ventura, CA

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Aj2

1874 posts in 1998 days


#6 posted 11-15-2018 07:05 PM

Those are really good looking table legs. I would mock the whole thing up with just the minimal amount of fasteners to see how much wobble there is.
My gut tell me you will not get a ridged table without adding a brace from leg to leg. This is your chance to be creative.
Go back to where you found the legs with a open mind and look around.
Good luck

-- Aj

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AZWoody

1413 posts in 1424 days


#7 posted 11-15-2018 07:15 PM

I would probably slot the holes side to side to allow any wood expansion or contraction. Will help in preventing some cracks or warping of the wood as the seasons change.

View Slade's profile

Slade

7 posts in 28 days


#8 posted 11-15-2018 07:50 PM

Its about 200lbs and ~10% MC. Noted on the slots side to side.

-- Slade

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NormG

6283 posts in 3204 days


#9 posted 11-15-2018 08:03 PM

Gorgeous legs. Maybe a 3 inch by the width of the legs, with bolts going through the leg. You place it wherever you think it looks the best

-- Norman - I never never make a mistake, I just change the design.

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bilyo

419 posts in 1302 days


#10 posted 11-15-2018 10:38 PM

Those are indeed handsome legs. I agree with Aj2, I think you definitely need a brace from leg to leg. Or, you could also place an angle brace from about the midpoint of the vertical part of the leg up to the table top at about a 45 to 60 degree angle. Especially with the larger top plate, I don’t think there will be a stability problem form side to side. But, from end to end, it will not be rigid enough without additional bracing.

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Slade

7 posts in 28 days


#11 posted 11-16-2018 07:59 PM

Thanks for all the feedback, I think i’m going to try for the below setup. Two sheets of 12×24 1/4 plates recessed, epoxy’d and screwed in and connected by a welded on 4×49 1/4 plate. I’ll then conect the legs with 4 bolts that are welded onto the 12×24 sheets. “Hold my beer” I’m goin for it.

-- Slade

View Knockonit's profile

Knockonit

477 posts in 402 days


#12 posted 11-17-2018 12:05 AM

me thinks, a rod drilled thru the web in lower legs, threaded, with deco nut on outside, and stop nut on inside might look decent, giving legs some stability, just an idea. not sure if it will solve the shake and possible bake issue.
Rj

or bend an rod and still thread thru legs at web and turn up to under slab and connect, this for srue would give table some solidity

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bilyo

419 posts in 1302 days


#13 posted 11-17-2018 01:01 AM

I think your plan will not give you the longitudinal rigidity you need.

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Slade

7 posts in 28 days


#14 posted 11-17-2018 02:16 AM

so i have to have another cross bar if i want this sucker to last and not fail, is what im hearing? something like one of these two options?

rough bar all the way through

or 45-60 deg angled brackets?

-- Slade

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bilyo

419 posts in 1302 days


#15 posted 11-17-2018 04:31 AM

That’s the idea. However, neither would have to be connected to the legs that low down. For instance, your angle brace could be maybe 6” to 8” down from the top. Actually, a combination of the two will give the most rigidity. If you do that, the triangle at the top could be even smaller.

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