Last week while wandering around the internet, I ran up on the Rafter Angle Calculator at Construction Resource.com. It looks like a nice resource, and it brought back some memories.
Once upon a time I was a rafter man on a framing crew. It seems far away now. It's been probably 15 years or more since I did much construction work. On days when I'm not out in the 100 degree heat, I miss both framing in general in rafter cutting in particular. [Actually out in the heat I don't miss it quite as much ;-) ]
After finding the "Rafter Angle Calculator", I did some further searching on rafter cutting. It appears to be a skill whose practitioners are dwindling. Or so they say. Pre-made trusses are one major factor in this. Curiously, while reading about the subject online I didn't notice anyone mentioning that rafters could be laid out with a framing square.
After learning to cut rafters from my Dad, I tried to learn more through reading and practice. One of the best was an old textbook cast off by some school. I'm going to have to hunt it up out of storage and find the title.
Eventually I might cut an entire roof ahead of or at the beginning of construction. In order to not have thousands of dollars of 2X6's cut wrong, I used a three-part safety system. I laid out the rafter with a framing square, calculated the length of the rafter with a Construction Master Calculator by Calculated Industries* (given to me by my boss), and used a rafter table booklet title Full Length Roof Framer by A. F. J. Riechers.** If these were the same, I was confident there was no mistake and the 6-1/2" worm drive Skil Saw was ready to take its bite. If you find a house with rafters that I cut it will have a pattern rafter (or more according to roof type) with all the information about the rafter -- cut, length, depth of seat cut, overhang, etc., as well as a signature of approval.
Those were the days.
Other info on roof framing
A Roof Cutter's Secrets to Framing the Custom Home by Will L. Holladay
Roof Framing by Marshall Gross (Carlsbad, CA: Craftsman Book Co., 1998)
Book Review of Full Length Roof Framer by Mike Merisko
Roof Framer's Bible: The Complete Pocket Reference to Roof Framing by Barry D. Musse
Basic Roof Framing Instructions online
*The Construction Master Calculator can calculate in feet/inches and figure pitch, rise, run, etc.
** The Full Length Roof Framer has been in publication since 1917 and is still not outdated.