How Thin Can A Top Be?

[custard]

I got a nice board of curly cherry today from Surrey Timbers. The luthiers had picked over the stack first so I was lucky to find one 10' board of quarter sawn, straight grained cherry with a pronounced curly figure across at least two thirds of the width. It's 6 1/2" wide and a full 1 1/8" thick. The board is rough sawn, but dry and ready to work, and it's surprisingly flat with virtually no cupping, wind, or bends.

I plan on using this board for the tops of a pair of bedside tables. These will be quite small at about 18" x 12", and the brief is "delicate". So slim tapered legs, some simple sycamore inlay, and a thin top. All pretty straightforward, leaving the beautiful curly figure of the wood to be the hero.

Here's the issue. I'd planned on jointing two pieces together to get the width, and there's enough material to do this. But what would make this piece really special would be bookmatching, with a matched band of exceptional curly figure about 9" wide running down the centre. However, if I go this route I'd have to be prepared for a top that's just 3/8" thick, 7/16" if I'm lucky.

Anyone any thoughts. Is this the way to get the best out of this fine board, or is 3/8" just too thin?

 

[joiner_sim]

'Im no expert but personally I'd say 3/8", 9mm is just too thin. I'd think the minimum for a top would be 5/8", 16mm. But from experience 18mm is the minimum I've ever done.

Your 9mm top could work if the timber is stable & well supported once constructed.

 

[CHJ]

Can your design accommodate a lipping around the top ?
If so why not treat it as thick veneer and glue it to a substrate such as MRMDF.

 

[carlb40]

What you could do is keep the top a reasonable thickness, and bevel the underside back towards the frame. That way you create the illusion of a delicate slim top.

 

[Cheshirechappie]

I think 3/8" would work, both structurally and visually. Many small tables have the edges of their tops bevelled on the underside to make them appear thinner than they are, and 1/4" to 3/8" at the edge is quite common and visually satisfying. The only proviso is that the rest of the structure must be similarly light in appearance, but as that fits the design brief, it's no disadvantage. Structural soundness will come from using good joinery technique, and cherry is a tight-grained wood that will suit lightness of form, too. It could work really well.

 

[Phil Pascoe]

Can your design accommodate a lipping around the top ?
If so why not treat it as thick veneer and glue it to a substrate such as MRMDF.

That was my thought , but with birch ply........but no reason why not mrmdf.

 

[marcus]

One issue I can see with a 3/8" top is how do you attach it? It's just about do-able but you wouldn't get a great deal of purchase with screws in timber that thin. Another problem is that since you will need to attach it in a way that allows for movement, there will not be much strength there when it starts to pull against the fastenings. Even though there is movement in the fastenings they will need to be done up reasonably tightly to keep the top secure and prevent cupping, and pulling against this resistance could cause the top to crack. That's two reasons why tops that need to look thin are usually made thicker and then bevelled at the edges....

If you go the veneering route you don't need exposed lippings. You can tongue and groove thin strips round the edges of the substrate, plane them flush, then veneer over them right to the edge. This can look pretty good on the right piece. Obviously you can't then bevel the underside, but you can get any thickness you want. You could maybe make them 1/2" or just over, which is still quite delicate, and thick enough to give a better purchase for the screws. Also the top will then be stable, so the movement issue discussed above will not be an problem.

One more thing (sorry, if I'm teaching you to suck eggs here), but if you decide to go this way don't use hide glue as the veneer will be likely to lift round the edges on the long grain sides (which is why traditional veneered work makes so much use of lippings and cross grain bandings). If you use a modern adhesive though you will be fine. It's a good technique.

 

[Eric The Viking]

I acquired a damaged table with a top that thick, some while ago.

I'm afraid it didn't survive. It was very delicate, possibly intended for the bedside, as the apron had runners for a missing drawer. It was pretty fragile, and Marcus is right - the top wasn't well attached (Mahogany, IIRC). Sadly it had a large scorch mark/burn on the top, and I thought at the time there wasn't enough to salvage, and didn't have the skills to repair/re-finish it.

It's worth mentioning another issue: in order to keep the proportions, the tapering legs were quite thin, and the apron was narrow - only about 2" high. The tops of the legs were no more than 3/4" square, leading to shallow and thin mortices, and a hanging drawer (apron on three sides only) wouldn't have helped, either.

When it got to me the legs hadn't split, but it was evidently suffering from being on carpet: obviously the legs dug into the pile and couldn't slide around (as they might on a plain floor), so the joints had worked quite loose with use. I think it was a prototype, and really too flimsy to be practical. When it was new it would have looked nice though - minimalist.

Practical issues, all. I'm sure you could design round them, but you'll need some meat in the apron construction to keep it together, or rails below to add rigidity.

Just my twopence.

E.
(not (yet) a furniture maker)

 

[Chrispy]

Can you panel the top? either in a frame that makes the over hang or set it in to the top of the side rails with no over hang, all flush like.

 

[Cheshirechappie]

Whilst I respect the contributions of others, I still think a 3/8" thick top would work. I'd overcome the screw problem by glueing slips of wood to the underside of the top in the button locations, to give a thickness of 5/8" to 3/4" to take the screws, taking note of grain direction and clearances to allow movement behind the top-rails. Using 5/8" thick buttons would still give total depth below top of less than 1", which would be easy to conceal behind even a very delicate top rail.

Solid drawer bottoms are usually about 1/2", and can take a lot of punishment. Provided the top did not overhang the base structure by more than 1/2" or so, I think it would survive normal use.

When my parents married in the mid 1950s, they bought a nest of occasional tables. The legs on these are 1" square at top, tapering to about 5/8" at bottom, and are about 18" long. They are held by a single m/t joint to the top rail, which is about 1 1/2" deep, and the top is about 5/8" thick, with standard button fixing. The top rails are about 3/4" thick, so the mortices must be 1/4" or close to. These have survived family life intact, and are still in use, having been refinished once about ten years ago. I'm not sure what the wood is, possibly something like afrormosia, but it's tight-grained and of medium brown colour. The design is very simple, very clean, very delicate and very satisfying.

 

[marcus]

It seems there are various ways you can get the top out of this bit of timber if you are determined, but I'm wondering if you are compromising the design you intended in order to fit the timber. Do you actively WANT a top 3/8 thick or is this thickness being chosen because you want to use this particular wood? If the later it may be best to find another piece and save this bit for something else .

Hard to say for sure without seeing the design but to me it feels a little bit thin even on something quite delicate. Personal taste, of course, and nothing a mockup can't decide one way or the other.

 

[custard]

It seems there are various ways you can get the top out of this bit of timber if you are determined, but I'm wondering if you are compromising the design you intended in order to fit the timber. Do you actively WANT a top 3/8 thick or is this thickness being chosen because you want to use this particular wood? If the later it may be best to find another piece and save this bit for something else .

Hard to say for sure without seeing the design but to me it feels a little bit thin even on something quite delicate. Personal taste, of course, and nothing a mockup can't decide one way or the other.

Marcus, the main objective is to show the curly cherry to best advantage by bookmatching. But bookmatching means a 3/8" or possibly 7/16" top.

I'd have chamfered the edges down to about those dimensions anyway (something I do with most pieces I make) so visually there's no difference. I did once make a pair of oak side tables with 1/2" tops, and as far as I know they're still going strong, but cherry's not as strong as oak and this would be even thinner, so I'm concerned about structural integrity.

Thanks

 

[marcus]

If it were me I would be asking myself what I would do if I could have the timber as thick as I wanted it. And if the answer was that I would have it thicker and bevel it then I would assume that I am being forced into a compromise i'm not quite comfortable with, and i would go and find some nice timber to book match at the thickness I need in order to do the top in a way I don't have doubts about....

 

[marcus]

To put it another way: why do you normally go to the trouble of bevelling your edges when you could save a lot trouble by just putting the top through the thicknesser a couple more times to get the finenss of edge you want? If the answer is "no reason, I've been wasting my time with the bevelling thing" then go ahead and do it at 3/8!