Saturday, March 02, 2013

plus or minus 2...

Woodworkers often have difficulty deciding on the proportion to make a box. I'm always aiming toward simplification, in the hopes of removing gumption traps. I want to make things as easy for my readers as they've become for me. Of course the easiest way to make a box with matching grain at the corners is to make a square box. But what if square bores you? What next?

I offer a simple design rule that can be used for making most rectangular boxes, unless there is something special that must fit inside. In honor of cognitive psychologist George Miller who passed away at the age of 92 last July, we can call it plus or minus 2. Miller had written a paper, on the Magical Number Seven, Plus or Minus Two, and whether or not you consider Miller's theory as valid, my own design rule might seem more familiar. A whole set of common proportions are based on this rule which to my knowledge has never been outlined or used as I will present. In other words, Google it and see what comes up.

3 x 5... 4 x 6... 5 x 7... 6 x 8... 7 x 9... 8 x 10... Are any of these pairs of numbers familiar to you? Some are the common sizes that you can have photographic prints made, and if you want to go buy a picture frame at Michael's to put your picture in, these are the sizes you will find. They also happen to be handy proportions for box making. And if you look closely, you will see that they follow the rule that if one side is x, the other will be x plus or minus 2. (+/- 2)

There may be a simple explanation for all this having to do with the sizes of paper easily cut from larger sizes. Perhaps a printer could tell. Or are there magical qualities to objects designed according to these proportions? In any case, a two inch spacer block works great when making a rectangular box. Put it in place for cutting the short side and then remove it for cutting the long. In other words, you can set up your stop block on the miter sled and make a box and have opposite sides fit perfectly, cutting them one after the other consecutively from the stock.

This is all a tease. In order to see this design rule in action, you will have to A) try it, B) attend one of my classes, or C) wait for the book.

Make, fix and create...


  1. Doug,

    Do you have any rule of thumb for the overall height of the box? Does the +/-2 rule apply in relation to the front or side?

    And is there really a book coming out, or was that just a figure of speech?


  2. There will be a new book coming out in the fall of 2014. Maybe a DVD, too.

    The height is another matter. What do you want to put in it? You could follow the same idea, that a 3x5 box should be be either 3 or 5 inches high. But the convenient thing for me is that I can make a series of boxes of various sizes using a single spacer block to alternate cuts between long and short sides, thus allowing the making of a box with grain matched corners, and no particular fussing about it.

    The proportion of the boxes that result, irrespective of height is pleasing.