How to work out minimum rail dimensions for a table

[fobos8]

Hi all

When I build a roof I look at the span of the rafters in a TRADA book and it tells me what dimension timber I can use.

Is there a similar kind of thing for table rails? Or is the approach no-scientific, back of a fag box kind of thing?

I'm making a table the top will be 900x1600x40 and made from US oak.

The legs will be made from 70x70 oak.

Would 70x45 be okay for the rails?

Cheers, Andrew

 

[MikeG.]

Aesthetics determines it......and the strength of the joints required to prevent racking. If it looks too frail, it probably is too frail.

Mike

 

[OPJ]

You should be able to get away with timber less than 2in. thick on a table of that size, in my opinion. Aesthetically, I think your rails should be closer to 4in. wide; either 95mm or 90mm finished width. Another consideration is in relation to the overall height of the table top - if you make the rails wider, can people still be seated comfortably underneath?

 

[fobos8]

if I go for 1 inch thick stock by the time its planed it'll be 20mm thick. 5mm for each tenon shoulder would leave a 15mm tenon.

Surely that would be too thin for a table this size?

45mm stock would give a thicker tenon.

......... or does it not matter how thick the tenon is - is it better to have a deeper tenon?


Your right 4" stock may be better than 3"- will get missus to draw it on autoCad. See how the proportions look.

Andrew

 

[OPJ]

As a general rule of thumb, the thickness of a tenon is equal to one-third of the rail thickness, or thereabouts, depending on what size your chisels are. With a table like this, I would consider making the tenons slightly thicker than this rule suggests...

I still think 1in. rails would be okay and you should even be able to get a 22mm finished thickness (usually, they are sawn generously between 27-30mm, which is significantly more than 25.4mm1in.! :wink. I think I would also consider a stretcher rail positioned central across the width of the frame, which would help to strengthen the frame further and prevent racking. They could be joined to the longer side rails using either a hidden, sliding dovetail housing (probably a bit much for a beginner...?), wedged through tenons or, some other method I cannot think of right now.

2in. thick rails do sound like overkill, to me. :? Then again, if you're already buying a load of 2in. stock, I can see how and why it could work out better financially and economically than buying a load of extra 1in. oak you won't be able to use here.

Another thought I had... To save on machining costs after you've had the sawn timber indoors to acclimatise, I'm wondering whether there is a forum member nearby who would be happy to prepare/help you prepare the boards at a fraction of the cost of what the yard would charge?

 

[woodbloke]

It's all to do with the proportions of the piece. If say, you were doing a fairly chunkable coffee table in oak, then you'd want the sizes of the rails to be commensurate with the overall feel of the piece. The same piece done in a lighter style in a less robust looking material would need the rails made correspondingly thinner, but always with the proviso that there's enough material to joint it adequately to the legs, so making them 12mm thick is leaving it far too thin to be able to make a decent m/t joint - Rob

 

[fobos8]

many thanks for the great input.

I think 1" rails might be a bit thin to support the heavy top. I'm gonna go for 2 x 4 " rails and do a 22mm tenon, which will be roughly a third of the width of the leg. This feels right to me.

Good idea OPJ about saving on machining costs. Any members live in Jersey, Channel Islands? ....... or anyone coming out here for a holiday with their planer



Gonna go and look through some oak at timber yard 2moro and maybe some other timbers. Ash?

All the best, Andrew