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Joint for attaching top to base for a knockdown table?

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Forum topic by leftcoaster posted 04-07-2019 01:04 PM 294 views 0 times favorited 8 replies Add to Favorites Watch
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leftcoaster

258 posts in 1264 days


04-07-2019 01:04 PM

I’m planning to make this trestle dining table. https://offermanwoodshop.com/store/hearth/tables/knock-trestle-dining-table/

Can anyone here make out how the top is attached?

More broadly – I will need to knock this down fairly often, so I’m looking for a way to join top and base that is sturdy yet undoable, while also not being susceptible to cracking from expansion.

Can some kind of sliding dovetail work?


8 replies so far

View Rich's profile

Rich

4478 posts in 977 days


#1 posted 04-07-2019 04:46 PM

I don’t know how they attached that one, since they don’t show it or describe it. If I were building a table like that and wanted it to be truly knock-down, I’d look into large dowels, like an inch or inch and a quarter. Four would do the trick and you could make two of the holes elongated by a fraction of an inch to allow for movement. The weight of the top will keep it in place.

-- Knowledge is not skill. Knowledge plus ten thousand times is skill. -- Shinichi Suzuki

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SMP

1034 posts in 293 days


#2 posted 04-07-2019 05:07 PM

Looks like just some bolts from underneath, just make sure to drill holes bigger than bolts and use washers.

View leftcoaster's profile

leftcoaster

258 posts in 1264 days


#3 posted 04-07-2019 05:27 PM



Looks like just some bolts from underneath, just make sure to drill holes bigger than bolts and use washers.

- SMP

So in the supporting member of the base, drill oversized holes, put lag screws and washers through?

I suppose one could put one lag screw in the middle that is not oversized and let the ones on either side handle the expansion?

View Bill_Steele's profile

Bill_Steele

515 posts in 2119 days


#4 posted 04-07-2019 06:21 PM

My guess is that there are counter-bored slots in the parts that attach to the top and screws are used to secure the top to the legs through counter-bored slots. Maybe like this picture….

I would suggest installing a threaded insert and using a bolt and washer—maybe 1/4-20 or 5/16-18—rather than a lag screw. If you plan to break the table down and reassemble it frequently, the hole (for the screw) may get damaged over time and not hold as well. You don’t need to buy the router bits shown above to create the slotted counter-bore, you can do as leftcoaster suggests and create overlapping holes with a Forstner bit and use a chisel to clean then up.

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a1Jim

117627 posts in 3965 days


#5 posted 04-07-2019 06:38 PM

All said and done any of the above should work as long as you provide for wood movement, you could also use some figure 8s on the inside of the top cross member, depending on screw size and amount of fig 8s it may not be as sturdy as the above ideas.

View Phil32's profile

Phil32

540 posts in 291 days


#6 posted 04-07-2019 06:49 PM

Assuming the upper cross members are attached to the table top, why not a wedge through the mortise & tenon joint at the top of the pedestal(s)?

-- Phil Allin - There are mountain climbers and people who talk about climbing mountains. The climbers have "selfies" at the summit!

View Rich's profile

Rich

4478 posts in 977 days


#7 posted 04-07-2019 06:53 PM

To me, knock-down implies no tools, just something to knock pieces loose, like those wedges locking the tenons. Things like screws from underneath are pretty obvious, but require a tool.

As I ponder this interesting problem, another idea that comes to mind is something similar to a keyhole cut into the horizontal members of the trestle lengthwise. Just a half inch long would do. You could drive screws into the bottom of the table top and set it down with them going into the round opening of the keyhole, then tap it sideways to set it into the neck of the keyhole to lock it down. That would allow the table to be lifted by the edges, which my earlier dowel solution wouldn’t.

If you want to be more fancy, you could do something similar with your sliding dovetail idea. The tail piece wouldn’t slide in from the edge, but rather drop in and then slide into place. Or the tail could enter from the side edge of the trestle, but that wouldn’t allow for movement.

-- Knowledge is not skill. Knowledge plus ten thousand times is skill. -- Shinichi Suzuki

View Tmanpdx's profile

Tmanpdx

23 posts in 99 days


#8 posted 04-08-2019 10:21 AM

I want to second Bill Steele’s advice. Threaded inserts with grooved slots and use washers.

I’ve built this type of trestle table 3 times so far, and it’s a great build. So sturdy with those wedge tenons.

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