The arched opening I’ll be using as an example in this article measures 36-in. If you want, you can also mark the ID of the jamb legs right on your straight edge so that you can easily transfer the chord length onto your work table. The ID of the jamb is what all of the casework must be registered from. Then I mark the center of the jambs on my straight edge and measure up, at that location, to the inside dimension (ID) of the head jamb.
This measurement is called the “chord length.” To measure the rise, I screw or clamp a straight edge horizontally at the intersection of the jamb legs and the head jamb. Measuring the width is easy just make sure you do it right where the leg jambs intersect the head jamb. The first step is simply to see what you’re working with. Here’s what works best for me and my crew. With the help of Gary Katz-and especially Todd Murdock, I’ve developed a dependable approach and have battle-tested it to be sure it’s accurate. Like a lot of finish carpenters, I’ve struggled to figure out a full-proof system for cutting radius trim on the jobsite.
That’s when it’s even more important to get a perfect fit and a good grain match, too! And occasionally we make radius casing that’s stained and top coated with fine finish.
#Sketchup number of segments is too many for given angle and radius full
Besides the sizes of the openings always being different, some openings require a full semi-circular arch, while others require just a segmental arch. Lately, my crew and I are installing a lot of flat stock casing in the homes that we trim out-which means I also have to make more and more radius casing to finish the tops of windows and doors that have arched heads.