Is this joint strong enough to prevent racking on it's own?

[Steliz]

I'm making a walnut coffee table which will have drawers below the top and no lower shelf like this

I would like to avoid putting any lower braces in to prevent racking so I need the leg/stretchers joints to be strong enough to allow this. Judging by a couple of posts I've found I should be fine but I thought I would ask anyway.
I will be copying the double M&T joint with a shoulder (https://i.imgur.com/CYv9ZyW.jpg) that MikeG used on his coffee table recently (thanks Mike) but my table legs are 420mm x 50mm x 43mm which is a little skinnier than Mike's and the stretchers are 110mm deep.
Is this joint strong enough to prevent racking on it's own?

 

[That would work]

100% yes.

 

[ColeyS1]

Absolutely! You could make it even stronger by reducing the size of the outer haunch (increasing tenon/glue area) and also adding a stubby tenon/haunch between the two long tenons.

 

[ED65]

Is a double tenon even needed on material only 110 wide?

Besides that it's a coffee table, what kind of racking forces are you expecting?

 

[MikeG.]

Absolutely! You could make it even stronger by reducing the size of the outer haunch (increasing tenon/glue area) and also adding a stubby tenon/haunch between the two long tenons.

These photos show why the tenons are the size they are:

If they don't interlock like this then they need to be shorter and mitred. Yes you could add a haunch between the tenons, but as with all joints, what you add to one piece of wood you subtract from another, and you'd thus be slightly weakening the leg with the additional haunch. Probably not significantly, though.

 

[MikeG.]

.......Besides that it's a coffee table, what kind of racking forces are you expecting?

I think a coffee table is one of the most vulnerable pieces of furniture there is, as it stands alone in the middle of a room, unprotected by walls. Kids climbing on it and adults stumbling against it, which wouldn't happen with say a side table (end table), mean it is particularly vulnerable in my view.

 

[Steliz]

OK, great, thanks for the replies.
The only racking I'm concerned about would come from someone dragging it across the floor. As it is a gift for a friend I want it to be robust enough to deal with that possibility.
On MikeG's table he used the double tenon to provide extra support and strength to alleviate the racking issue and, as I'm relatively new to this, I borrowed from his experience. If others think it's overkill then that's OK but I will do it anyway for my own reassurance.

I will post this in projects soon but I wanted to be confident that the wood I have for this was going to be OK as the boards started off with a lot of cupping and twisting. Now that they are planed and roughly dimensioned they seem to be fine.

Steve.

 

[That would work]

Is a double tenon even needed on material only 110 wide?

Besides that it's a coffee table, what kind of racking forces are you expecting?

No they are not.
Double tenons are usually reserved for things that are subject to racking such as doors which are under constant racking vulnerability.
A coffee table simply is not and therefore there's no benefit, apart from to you if you like doing them that is :roll:

 

[ColeyS1]

One of the perks of having a haunch between the two tenons is you dont have a straight through joint. If for example the double tenon arrangement was a bottom rail on a door,any slight movement of the joint would in theory allow water to go straight through. The part between the tenons at the moment is just a straight butt joint. Glue doesn't stick as well on endgrain.

Sent from my SM-G960F using Tapatalk

 

[MikeG.]

.......A coffee table simply is not

Until someone bumps it.

and therefore there's no benefit, apart from to you if you like doing them that is :roll:

Why the rolling eyes emoticon?

There is a benefit, but it may have been lost on you. The benefit is that you can have a full depth tenon. If you have orthodox single tenons then adjacent ones meet in the middle of the leg and so are truncated. In a slim leg this can mean tenons only maybe 15 or 20mm long.

Certainly with aprons only 110 wide double tenons would be small and somewhat fiddly. Single tenons but staggered (top and bottom) and haunched would allow full depth joints which orthodox M&Ts wouldn't.

 

[ED65]

...I will do it anyway for my own reassurance.

Nowt wrong with that, good practice if nothing else.

While I wouldn't argue that building stronger is not a good thing something to bear in mind for the future is stubby tenons and 'just' dowel joinery have been and still are used for the very same joint in tables of all sorts and have proven themselves good enough in most cases.

You do find double/forked tenons in old furniture pieces, but other similar pieces are just as likely to have a single wide tenon. This is without pegs, drawboring or wedging, all of which can be used to increase strength and long-term security, with minimal additional work needed.

 

[thetyreman]

it'll be insanely strong you don't need to do the double tenons, but it'll add even more strength.