Compound Angles; No Math
Once you understand ‘resultant’ angles, sawbenches (and chairs) are easy.
by Christopher Schwarz
Most first-time chairmakers are intimidated by the compound joinery used to fasten all the legs, stretchers, spindles and arms. The truth is, it can be quite complicated if you try to figure out everything using trigonometry. But if you take some lessons from other chairmakers (like I did more than 10 years ago), there are easy ways to design and build chairs without math.
So put away the scientific calculator and fetch some scrap pine, 12-gauge steel wire from the home center and needlenose pliers. We’re going to design and build a simple sawbench with five pieces of wood and compound angles.
When chairmakers talk about the angles of chair parts, they use the terms “rake” and “splay” to describe them. Rake is the angle of the legs when you look at the chair from the side. The front legs rake forward; the rear legs rake back. Splay is the angle of the legs when you look at the chair from the front. Chair legs splay out.
I don’t mess around with describing or measuring rake and splay much, except to explain it to other builders.
Instead, I use what is called the “resultant angle” – one angle that describes both the rake and splay. You can calculate this angle with trigonometry, but there is a simpler way to think about compound leg angles for those who consider mathematics a cruel master.
The resultant angle is not measured from the front or side of a chair. Instead of looking at a chair from the front or side, you look at the chair from a position in space where the leg doesn’t appear angled at all.
Video: See how to level the legs of a sawbench with simple tools.
Blog: Learn how to cut wooden wedges on the band saw.
Web site: Visit Country Workshop’s web site for more information on chairmaking.
To buy: Drew Langsner’s “The Chairmaker’s Workshop”
In our store: “Make a Windsor Chair with Mike Dunbar”
From the June 2015 issue