Joint advice

[Mike Saville]

Thanks for all the reponses so far. I have some 3/4" Oak which I'm going to use to make this project. So thickness of top/shelf will be around that.

As far as the joint goes it seems I have a couple of options (aside from screws).

First is to use dowels like so:

Second is to use a tennon - like this I think :?:

I'm more in favour of the tennon but suspect the dowels may be stronger. Is this correct?

Mike.

 

[Anonymous]

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[Colin C]

Welcome Jimjam

You could use the dowels but make the legs a little longer on top, which would not change the design much, but which would the more strength in the top of the leg.

I hope that is clear

Ps On the side that has the one dowel showing , i would put a false dowel in as I dont think it would look right the way it is.

 

[SimonA]

JimJam,

I'd go with the tenon.

You said your going to be using 3/4" boards for the top so I would have a 1/2" tenon but have it flush with the underside of the board, then that would leave 1/4 shoulder on the top. So instead of having 1/4" shoulder, 1/4" tenon, 1/4" shoulder. You'd have 1/2" tenon, 1/4"shoulder.

If you go for dowels then I'd have to agree with Colin C I don't think the three dowels showing looks very good. It would be a cleaner design if you just had a single visable dowel in either side.

I still think the tenon is the stronger joint.

SimonA

 

[engineer one]

i think that you need to put cross rails at each end under top and shelf
to give you the major support. not sure the tenons will be long enough to stand the strain :roll:

paul :wink:

 

[SimonA]

JimJam....

What are the over-all dims on the coffee table?

SimonA

 

[sawdust maker]

Hi

Looking at your diagram for using dowels. I don't think it will work. The side where you have one dowel appears it would be cut by at least one of the other two dowels.

Paul

 

[Chris Knight]

I think the tenon will be more than strong enough. The structure also has the lower shelf to help stiffen it and people underestimate what a good end grain glue job can do.

In some extensive testing of end grain glue joints (touched on here https://www.ukworkshop.co.uk/forums/view ... 6157#16157 ) I found that using Balcotan PU glue and also Sheppy Tug scotch glue, I could glue 1 inch square butt joints (end grain) in pieces of white oak 6 inches long (for 1 foot total) that could not be broken with a 3lb club hammer when hit with all my strength sideways on. Repeated blows eventually fractured the joined wood but not at the glue line.

Oak has big pores but tyloses make them pretty impermeable - where this may place oak in relation to a similar experiment with walnut I don't know but I wouldn't expect walnut to come out worse as it is open grained with less abundant tyloses.

The weakest part of the joint is the end grain in the leg above the joint, thus the tenon tongue should not be made too big requiring a deep mortice (I would go for 3/8 inch). As drawn there is also long grain contact in the joint (albeit at right angles between leg and top which will offer increased strength.

If in doubt make a test piece. In my tests I found that the glues I named worked extremely well but the other PUs and Scotch glues did not work nearly as well in this joint configuration, so I recommend that you "accept no substitutes"!

 

[Shultzy]

I'd go with Simon's 1/2" tenon, 1/4"shoulder, with maybe a metal plate inset into the underside to strengthen it. I would prefer two dowels on either side of the leg, but of course the corner two would have to be false.