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Threaded rod through table top

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Forum topic by Lodewijk posted 01-17-2017 07:22 PM 1470 views 0 times favorited 13 replies Add to Favorites Watch
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Lodewijk

5 posts in 329 days


01-17-2017 07:22 PM

Topic tags/keywords: desk top threaded rod joinery movement question kiaat desk study desk

Hi there everyone,

I am new to this forum, and this is my first post.
I would like to ask some advise:

I am building a study desk. The top (and desk) will be made from Teak (actually a local species from Southern Africa, known as Kiaat). The top is 1.9m x 1.0m x 40mm (approx. 75” x 39” x 1.5”). The top is made up of 4 planks, each approximately 250mm (approx. 10”) wide. What I have done is that I drilled 16mm (approx. 5/8”) holes through the planks, and installed M12 (approx. 1/2”) threaded rod across the width of the top. The threaded rods are therefore slightly shorter than 1.0m (39”). I glued the planks together, put the threaded rods through all 4 planks, put nuts and washers both sides, and tightened the nuts well. Afterwards I clamped the top, using bar clamps and cauls, and let it dry. The nuts and washers sit in a counter bored hole and I have plugged the hole, so the nuts are not visible / accessible. The top will then sit on a sub frame which is 20mm (approx. 4/3”) thick. The sub frame will be flat, so not like an apron working about its strong axis. I am planning on bolting the top to the sub frame using M8 wood inserts, and slotted holes in the subframe.

I am wondering about the possible downsides in terms of durability, to what I have done. Does anybody have any experience with this sort of thing? What are the pros and cons?

I attach a few pictures to hopefuly give a better idea of what I’ve done.

-- Lodewijk, South Africa


13 replies so far

View HerbC's profile

HerbC

1685 posts in 2694 days


#1 posted 01-17-2017 09:51 PM

The wood is going to “move” across the width of the panel due to seasonal changes in environmental humidity. If it shrinks it probably won’t cause much of an issue. If it tries to expand you will probably see damage eventually.

Good luck!

Herb

-- Herb, Florida - Here's why I close most messages with "Be Careful!" http://lumberjocks.com/HerbC/blog/17090

View papadan's profile

papadan

3584 posts in 3203 days


#2 posted 01-17-2017 10:23 PM

Your threaded rods serve no purpose except to restrict wood expansion. I would remove them and reseal the holes on the edges.

View johnstoneb's profile

johnstoneb

2636 posts in 2008 days


#3 posted 01-17-2017 10:33 PM

I would just leave them in there. I have seen bench tops bolted together this way and no problems after many years.

-- Bruce, Boise, ID

View wuddoc's profile

wuddoc

231 posts in 3553 days


#4 posted 01-17-2017 11:19 PM

My coffee table workbench top is secured with all-thread similar to what you are doing and has stayed together for over 20 years.

The old maple top woodworking labs benches you use to find in schools years ago used all-thread to secure the top pieces together. I discovered this when I wanted to convert a 4 student place with vices 5’ x 5’ bench top to a 2 vice 3’ x 5’ bench.

-- Wuddoc

View Lodewijk's profile

Lodewijk

5 posts in 329 days


#5 posted 01-18-2017 04:29 AM

Thank you for the replies so far.

It seems I have two votes “Good” and two “Bad”... I might have a 50 : 50 chance of it being ok. I will finish the top all round with three or four coats polyurethane, the short ends with seven or eight, and hope for the best.

-- Lodewijk, South Africa

View shipwright's profile

shipwright

7779 posts in 2633 days


#6 posted 01-18-2017 02:30 PM

You are fine. Solid wooden rudders have been made this way for centuries and then immersed in seawater.
You won’t be seeing any problems from wood expansion.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

View TObenhuber's profile

TObenhuber

156 posts in 1427 days


#7 posted 01-18-2017 03:12 PM

I’ll start with welcome to LJ. Its a great community.

Second, I haven’t tried this method before but it seems like it could look awesome with the bolts showings. Depends on the customer and what they plan to do with it.

If you are still worried about the wood movement, I suggest try it. If it falls apart, it will not be tomorrow. Probably won’t even be this year or it a few years. I have done several laminated tops that are pocket holed through the mounting surface. All are still intact and have been moved across the US a few times. None of them are showing signs of falling apart. I think you have the dimensions working for you, the 1.5” thickness (what I generally use as well) is very strong. Will your table last through the centuries, none of us will know.

Have to keep that in perspective.

Here are examples I have made with laminated top. Nothing but glue. Held down by pocket screws from the base. Maybe it won’t last for a thousand years but my wife loves them. In my book, that’s what’s important.
http://lumberjocks.com/projects/178594
http://lumberjocks.com/projects/101403

-- Travis, Virginia, www.facebook.com/CreativeWoodworksHybla

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TObenhuber

156 posts in 1427 days


#8 posted 01-18-2017 03:19 PM

Another though, if you want to prevent some expansion problems. Maybe drill the holes in the base over sized and the holes in the bottom of the top with pilot holes. Use some washers for the screws/bolts. The washers will allow the screws to clamp the base to the top but the over sized hole should allow the top to move with out causing issues with constriction from the base. Just an idea.

-- Travis, Virginia, www.facebook.com/CreativeWoodworksHybla

View Nubsnstubs's profile

Nubsnstubs

1207 posts in 1565 days


#9 posted 01-18-2017 03:27 PM

I don’t know about the Teak you are using, but in general, Indian or Asian Teak is supposed to be the most stable wood there is. More than likely, not an issue. ............ Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

View AlaskaGuy's profile

AlaskaGuy

3645 posts in 2144 days


#10 posted 01-18-2017 04:20 PM



My coffee table workbench top is secured with all-thread similar to what you are doing and has stayed together for over 20 years.

The old maple top woodworking labs benches you use to find in schools years ago used all-thread to secure the top pieces together. I discovered this when I wanted to convert a 4 student place with vices 5 x 5 bench top to a 2 vice 3 x 5 bench.

- wuddoc

Yes, our schools here have many old work tables build like that.

-- Alaskan's for Global warming!

View Lodewijk's profile

Lodewijk

5 posts in 329 days


#11 posted 01-19-2017 07:06 PM



Another though, if you want to prevent some expansion problems. Maybe drill the holes in the base over sized and the holes in the bottom of the top with pilot holes. Use some washers for the screws/bolts. The washers will allow the screws to clamp the base to the top but the over sized hole should allow the top to move with out causing issues with constriction from the base. Just an idea.

- TObenhuber

Thanks for the suggestion, I am definitely going to allow for some movement with oversized holes or slots.

-- Lodewijk, South Africa

View Lodewijk's profile

Lodewijk

5 posts in 329 days


#12 posted 01-19-2017 07:16 PM



I don t know about the Teak you are using, but in general, Indian or Asian Teak is supposed to be the most stable wood there is. More than likely, not an issue. ............ Jerry (in Tucson)

- Nubsnstubs

Hi there. You got me interested in learning a bit more about the Teak I’m using. Its not in fact the same as Indian Teak, but called African Teak. Interestingly it also resists movement due to moisture, which is probably why they called it Teak. Some other very interesting properties, such as the magical medicinal properties of the red sap :-)

African Teak, with magical healing red sap

Indian / Asian Teak

-- Lodewijk, South Africa

View johnstoneb's profile

johnstoneb

2636 posts in 2008 days


#13 posted 01-19-2017 08:46 PM

Kiaat, muninga, narra are all names for your wood. It is closely related to Padauk. pterocarpus. It is softer than African paduak and does resemble teak and maybe a substitute for teak in that it is used in shipbuilding

-- Bruce, Boise, ID

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