hello freinds,
I can’t seem to get a sense of what is a general set of practices for determining case thickness when designing a piece of furniture. From the largest freestanding wardrobe to the smallest jewelry box. Sure it seems that if you are using softwood you should go thicker. But I can’t seem to find any articles or books that start with a set of practices like that. any ideas?
thx!
Replies
That's a good question. Most books with furniture plans give thicknesses of about 3/4 to 7/8 inches for case work. Smaller parts or pieces range from 5/16ths down to 1/8 inches. I have not noticed any differences in hard or soft woods in what I have read. Surely, for sturdiness and load bearing ability the larger furniture should be thicker, but I have never read any rules of thumb. I made a search entry of "rules of thumb" and over 10000 entries popped. A quick glance a the first couple of pages, and I found an interesting short article by Strother Purdy. It was more about grain and not thickness.
https://www.finewoodworking.com/membership/pdf/7487/011130088.pdf
There are conventions concerning the thickness of various furniture parts, often determined from the their function and sometimes from the strength or stiffness of the wood species used ..... but they vary a great deal with different styles of furniture.
In stuff such as kitchen furniture of the modern sort (basic cases with various widths, inserts and door styles) the convention is to have parts that are between 16 - 19mm thick. Some bespoke stuff might go up to 22mm but it's rare to come across anything as thick as 25mm (1 inch).
In traditional solid wood furniture, some styles emphasise a slim and elegant look, requiring less thick sides or tops. Scandi-modern can be like that, looking almost fragile, although use of a strong timber such as beech or ash compensates for the thinner sections.
Some styles go for a much heavier or even over-engineered look. Some of the Arts & Crafts styles are like that - Mission, Cotswold, Greene & Greene and some others often look (and are) extremely substantial.
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As you make furniture, including some that's your own design - albeit based on one or more well known styles - you begin to get an "eye" for the "right" thickness of this part or that. Conversely, your "eye" also recognises when the thickness or other dimension of a part is "wrong" for the style you're trying to emulate.
As far as I know, there isn't a definitive or summarised list of "thickness of parts for various furniture styles". However, if you read the various make-it articles in the likes of Fine Woodworking or other such sources, you can pick up the conventional thickness dimension for the usual parts of various furniture types & styles of the more popular kind.
On the other hand, some woodworking magazines seem able to show only the Klunker style, no matter if they call it by some other style-name. The klunk seems to come from a desire to ensure the often ugly thang won't fall apart, with the consequent avoidance of any kind of elegance. :-)
Lataxe
I don't know of any "rule of thumb" and it may be because it's too complicated.
Not only do you need to consider the thickness of the stock, the species of wood but also what type of joinery is to be used. You also need to factor in how a piece is to be used. Is it going to be subjected to heavy use or is it more of an aesthetic piece.
IMO this is not something that can be easily expressed or formulated but with experience and the benefit of history you get a "feel" for what works.
Make it thicker or thinner than what you can buy at an orange or blue box. 3/4" will always look like flatpack. Varying parts' thicknesses within a piece adds character.
There are no 'rules of thumb' but building something too far away from what you see for items of similar proportion is probably unwise. These proportions have been developed over time to make reasonably efficient use of material.
Quite often 3/4" is used for casework, but this is probably not really for structural purposes - if you saw wood an inch thick wet, you can probably get 3/4 inch thick dry finished boards from it.
Cutting thinner is possible but minor errors can lead to more boards that are a bit thin in places if cutting by hand so inch multiples it tended to be, and of course planing by hand to make it thinner is a lot of work for little visible benefit, so from that we have the expected aesthetic of 3/4 inch.
This size is also strong enough to survive rough handling in almost all portable furniture, allows secure joinery and is not so thick as to add unnecessary weight.
As timber gets thinner, it is able span shorter distances without bending and joinery adds less stiffness so you need more supporting structures and more boards to bear the same amount of load.
How you incorporate this into your design is a personal choice - you can have very thin boards attached to a robust frame, or thicker boards that are themselves the frame, you can use lots of joints to create a phenomenally strong structure from thin boards or fewer thicker boards with more space but a heavier structure.
As others noted, the thickness can sometimes be for structural reasons. But more often than not, it's a matter of what looks good.
Look at lots of pictures of furniture, and notice things like thickness. See what works, and what seems off.
As MJ said, stock 3/4 inch seldom seems quite right to me. It's either too thick or too thin. For case sides and drawer blades, I like something closer to 7/8. I don't get hung up on exact thickness, either, and don't usually measure. As long as all the parts are the same thickness, when the look right, they are right.
As far as visual design goes there are lots of rules and theories and published books and articles and university courses that deal with that subject. A good place to start I think is with Classical Rules of Order. Ancient Greeks figured out so much about how the design of the parts of something affect how we see the whole thing. They were the first and maybe even the last word on that subject.
Tastes are subjective and change through time of course so whatever we say today is beautiful and good design someone someday will say " I don't like that ,it soooo 2020's".... and then at some point it'll be fashionable again. Someone mentioned the boxie look from home improvement store type furnishings as being unpleasant but in the 80s when "Euro" style (boxie) cabinetry started showing up people couldn't get enough of it! It became everyone's dream kitchen.
We have graphic standards that for the most part tell us the height of a table top or chair seat but I haven't come across anything myself that tells me the minimum structural requirements for building a piece of furniture. Such as: 4 oak sticks of a certain thickness attached to a board made out of elm will hold up a man sitting on it but if made of pine would need to be increased by a factor of x. Engineering requirements exist for most other things. For buildings, down to the exact number and length of nails. Calculated charts for length and thickness and spans by species etc.
There are published scientific studies of the structural properties of probably every type of wood but what that means or how to utilize that information for building a piece of furniture I haven't come across. If it exists then you would think that the larger furniture manufacturers would have that information, but then ikea was making those chests that were crushing kids so .....
I have a set of dining chairs, they're light but pretty sturdy. They function just like a chair should but my wife has this woman friend who comes by who is really huge! When she sits on one of those chairs I wince every time!
This question roamed about my head for a while after my first answer, unearthing one or two other bits of info.
As John_C2 mentions, much of the designed-in thickness of a piece of furniture's parts is driven by aesthetics as well as by (perhaps even instead of) function or engineering considerations. But some furniture elements have to be driven primarily by function or there'll be a failure.
The most familiar example is probably that of load bearing shelves. Make them too thin, long or of intrinsically bendy material and they'll sag when loaded even lightly. There are tables showing the amount of sag that'll result for a given shelf length, thickness, material and the like. Fine Woodworking, for example, references "the sagulator":
https://www.finewoodworking.com/2007/01/05/engineer-shelves-with-the-sagulator
The general principle of the sagulator can be used, perhaps in a less precise way, to consider the necessary minimum thickness of other load-bearing parts of furniture, such as table tops or anything with some form of cantilever in it, such as desk lopers. A workshop bench needs a very sturdy top, for example. Some heavily-loaded items that stand on long legs may need a certain minimum cross-section for those legs.
But even for these kinds of high-load bearing parts there are alternative approaches to that of increasing thickness, which provide additional support in other ways - brackets, batons, lippings and other parts that counteract sag or other inclinations to bend. These parts can be decorative as well as functional - nicely shaped brackets or battens; carved motifs on lippings.
Lataxe
Korsak, Hunter, Miller, Becksvoort, and others have written good articles about how to add sturdiness to load bearing parts of furniture and to strengthen thinner surfaces.
https://www.finewoodworking.com/2018/07/13/construction-favorite-articles
https://www.finewoodworking.com/2017/05/31/lighter-stronger-frame-panels
Here's another article that also lists a couple of references for helping to design case thickness:
https://www.finewoodworking.com/membership/pdf/6677/011068036.pdf
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