From the publisher:
Two Books in one!
You get Manual of Screw Cutting 4th edition (1887) containing rules for calculating the change gears on screw-cutting lathes to cut square and angular threads per inch or per pitch, with two or four gears. Also, useful rules for calculating the diameters and speeds of pulleys.
Topics include how to cut a thread without reversing or stopping the lathe, how to find two gears, how to cut fractional threads, how to measure fractional threads, how to find the set required on a screw cutting tool, how to find the diameters of pulleys, how to prove four gears, strength of tapping holes, how to cut double of treble threads, and more.
Then you get Change-Gears from 1935. Calculating auxiliary change-gears for cutting special threads or pitches not within the range of the regular quick-change gear-box; A method of utilizing various settings of the gear-box to avoid using special auxiliary gears.
You get change gear formulas, examples of calculations, compound gearing for thread cutting, number of threads per inch cut with given combination of change-gears, change-gears for metric pitches using English lead-screw, when the lathe has a metric-lead screw, translating gears for metric pitches, and more.