# 3/4" dowel - how much weight supported



## klr650 (Apr 4, 2010)

I'm going to be using a 3/4" walnut dowel to support a shelf and i wonder how much weight I can expect to support with it.

The design is for a 3/4" dowel - a 1"x1" bar turned on the lathe to 3/4" dimensions, glued into a walnut socket.

The socket is only about 3/4" deep.

Essentially what I'm making is a simple shelf supported by an arm


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## klr650 (Apr 4, 2010)

*never mind maybe...*

I found the link above in the sticky section listing mechanical properties of wood. I'll root around after work to see if my question is answered there.


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## BWSmith (Aug 24, 2010)

This sort of a "Martha"....I knew then and do now that we could probably do better?But 25 years ago when building our kitchen cabmets.....being on the edge of brokeness.....I drilled 1/4" holes for shelf supports.Anyhow,1/4" Birch dowels being noticably cheaper than proper brass shelf supports,I used the dowels.Uhhh,25 years,4 wide open boys,wife who can't cook,and the dowels are still there.I believe you could climb up the shelves and not worry about shearing them off.BW


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## woodnthings (Jan 24, 2009)

klr650 said:


> I'm going to be using a 3/4" walnut dowel to support a shelf and i wonder how much weight I can expect to support with it.
> 
> The design is for a 3/4" dowel - a 1"x1" bar turned on the lathe to 3/4" dimensions, glued into a walnut socket.
> *The socket is only about 3/4" deep.*
> Essentially what I'm making is a simple shelf supported by an arm


I don't think you will find the answer in any strength of materials book.
Your design has an inherent weakness, the socket depth. All the downward forces are trying to pull the dowel out of the socket, rather than break the dowel, which might show up un the "book".
I would consider a "design change" possibly to a wedged dowel that goes through to the other side, leaving the full 1" bore, then a reduction if you chose, from the board outward.
A wedge will increase the strength dramatically. The whole science of concentrated loads and distributed loads,cantilevered loads, shear forces and "moments" is a bit complex. The backyard boys just "overkill" and usually that works. A true test would be to make the joint as a mock up, there I go again, and then hang some weight on it until it fails. Then you'll know exactly...well only if you make 10 of them and take the average. :laughing:


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## H. A. S. (Sep 23, 2010)

I'm sure there is a formula in my Bible, but it's too damn cold to go get it.:icon_smile:

A lot of the forces depend on the layout of the shelf, especially lengths.


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## BWSmith (Aug 24, 2010)

Wood,IMO....its very much a case of diameter vs seating depth on the pullout thing.Kinda like why a 1x4 brace is harder to pull-off than a 2x4 when nailed to a post....everything else being equal.BW


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## BWSmith (Aug 24, 2010)

Oh yeah wood,google a "Putlog scaffold".........I swear,we've used them to VG effect(its a wedge thing).BW


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## klr650 (Apr 4, 2010)

woodnthings said:


> I don't think you will find the answer in any strength of materials book.
> Your design has an inherent weakness, the socket depth. All the downward forces are trying to pull the dowel out of the socket, rather than break the dowel, which might show up un the "book".
> I would consider a "design change" possibly to a wedged dowel that goes through to the other side, leaving the full 1" bore, then a reduction if you chose, from the board outward.
> A wedge will increase the strength dramatically. The whole science of concentrated loads and distributed loads,cantilevered loads, shear forces and "moments" is a bit complex. The backyard boys just "overkill" and usually that works. A true test would be to make the joint as a mock up, there I go again, and then hang some weight on it until it fails. Then you'll know exactly...well only if you make 10 of them and take the average. :laughing:


Pullout is a concern, I thought about it, but can't really do anything about it from behind - the back isn't exposed.
Possibly I can add a thin wire diagonal brace to reduce the downward sag or simply angle the hole slightly upwards and add a brass collar. 
Since this will be supporting upwards of 15 lbs, I probably should add in that brace.


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## woodnthings (Jan 24, 2009)

*There are many other ways*

To support a shelf.."Z" bars, French cleat, before you settle on the dowel look for some shelf/cabinet hardware sites.
Somethin' like this:
http://www.hooksandlattice.com/cleat-hangers.html

http://www.rockler.com/product.cfm?page=17507
and this: http://cgi.ebay.co.uk/PAIR-Concealed-Hidden-Shelf-Support-Bracket-/200274571361

OR, you could drill multiple holes for dowels into the back side of the shelf, assuming there is enough thickness to allow it, and support it likea fireplace mantle...all blind support no brackets or dowels showing.
 bill


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## klr650 (Apr 4, 2010)

Either way, looks like I got some research to do. This wood sculpture that I've been working on is really stretching my abilities.

Best I do some mock up work this weekend before committing.

It's funny you mentioned french cleat - I was just thinking the same thing.


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## klr650 (Apr 4, 2010)

I have a solution for this that I think will work fine.

Drill the hole as normal, then from the side of the mounting surface drill a 1/4" hole through the dowel, and insert a pin to lock it in place. should be a strong joint that won't pull out.


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