Bronze table legs to be attached to table slab - Screws size? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 8 Old 10-15-2008, 11:11 AM Thread Starter
 
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Talking Bronze table legs to be attached to table slab - Screws size?

Dear all,
I am nearing the completion of a custom made table and in order to get things wright your advice would be very much appreciated.
I have to fix these bronze casted table legs (Pic 1) to a blackwallnut table slab (Pic 2 - 33Kg - 1450x750x50).
I have not had the holes drilled on the top discs (2 cm of height) of the table legs yet but I was thinking of having 3 holes drilled as in Pic 3.
At this point my questions are the following:
- What should the screw size be? (lenght - shank/thread diameter)
- Need the holes to be drilled into the top discs to have the same diameter as the screw`s shank? Any advise on the diameter I should choose?
- The table slab is 5 cm thick, how deep should the screws go into the wood?
I look forward to hearing from you.
Cheers
Simon
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post #2 of 8 Old 10-15-2008, 12:56 PM
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I would probably use 1/4" or 5/16" (or whatever equivalent sizes in metric) lag bolts. I would drive these 4.445cm (1 3/4") into the table top. You would have to purchase a lag bolt that would give this depth into the wood plus the thickness of the top of the bronze leg.

Even at that I just do not think that 3 bolts in each of two legs in that configuration are sufficient to hold that huge top. There are going to be some large multiplied (lever arm) forces involved at the edge of the table. I do not know how you would do it with those ready made legs, but I think you need some additional bracing.

George
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post #3 of 8 Old 01-25-2009, 07:41 PM
 
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simon,
where did u get the bronze table legs. and did they support the table top
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post #4 of 8 Old 01-26-2009, 09:00 AM
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It will look great

I wouldnt feel comfortable with a large top on such a small mounting surface on top of the legs. What I would do is make a 12" Diameter 3/4" plywood disc for each leg. I would use nuts and bolts to hold it to the leg sections. Then I would use screws to attach the walnut top to the plywood. This would spread out the load forces.
Another potential problem I see with this set-up is that the top may be too wide for the legs and the table might tip over if someone leaned too hard on the edge. Maybe someone else will chime in here.

As for how far to put screws into the top? I would stop about 1/4" from the top surface. I think that would be about 15mm?. Sorry, I dont have conversion tables handy

I think it will be a great looking table.

Tony B



Retired woodworker, amongst other things, Sold full time cruising boat and now full time cruising in RV. Currently in Somerville, Tx

Last edited by Tony B; 01-26-2009 at 09:11 AM.
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post #5 of 8 Old 02-08-2009, 12:12 AM
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Simon,

Tony brought up some valid points, including that it will look dynomite.

I would have a machine shop drill and tap 4 holes into the tops of the bronze legs, then bolt a large (maybe 16" square) piece of 1/2" steel or brass plate to it down through the plate into the bronze legs. Cast bronze is difficult to machine, and new carbide or cobalt alloy drills with a lot of down pressure and coolent are necessary. You probably won't be able to do it with hardware store drills and a hand drill.

This way you can cut way down on the leverage applied in tension to the screws going into the top that George mentioned, and you can use a large number of screws as well.

I would have someone with a vertical milling machine cut some elongated (slot-shaped) holes in your plates to screw through up into the top.

Or actually, you could just drill the holes quite a bit larger than the screws and use thick washers under the heads. That way the top will be able to expand and contract across the grain with changes in moisture content.

The only problem that remains is how tippy the top will be due to the width of the slab. My gut feeling is that it will probably be all right.

Best of luck.

Cheers,
Jim

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Last edited by clampman; 02-08-2009 at 12:48 AM.
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post #6 of 8 Old 02-08-2009, 05:49 PM
 
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I would use brass threaded inserts(self tapping for wood) available in inch or metric. A 9mm hole in the bronze will give you room for a 8mm or 5/18-18 hex head bolt. As far as drilling the bronze center drill the hole first. You can use a high speed(standard) drill bit in a hand drill at half speed with a drop of oil every now and then to help keep it lubed. Make sure the legs are clamped when drilling because when you break through the bronze the drill will want to grab. It will be a little tuff but can be done. I'm a machinist for 35 years. Good luck
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post #7 of 8 Old 04-24-2009, 11:42 PM
 
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Smile Help!

Hi Simon....no clues fro the actual attachments of the legs. You could email my hubby at [email protected] We are a manufacturer of fine furniture and custom fitted cabinetry in Toronto, Canada. He would be of help I'm sure.
I would like to purchase those legs for my black walnut live edge table top too. Can you share? Thanks, eh?

Last edited by [email protected]; 04-24-2009 at 11:44 PM. Reason: cause I cannot spell when sleepy!
post #8 of 8 Old 04-26-2009, 08:55 PM
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Older thread!

HELLO..THIS POST IS FROM OCT 15 2008
Probably not useful info at this point!
Don't even think of directly screwing those legs to that piece of wood without an additional support plate in between them! This is based on practical experience and the strength of materials classes I took many years ago. Imagine a person weighing 250 LBS leaning on the far edge of the table to get out of their chair. The force would shear off the screws or tip the table as well. A metal plate as clampman suggests or a wooden brace to distribute the load as on a shaker style table would make a much better/safer solution. My opinion only. Where are you posting from? Question because you gave metric dimensions.... 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)

Last edited by woodnthings; 04-26-2009 at 08:59 PM.
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