Cutting time = length of cut / (feed per rev x RPM) for turning and drilling, or length / feed in IPM for milling, times the number of passes. A 4 inch turning pass at 0.005 inch per rev and 600 RPM takes 1.33 minutes.
This is time in the cut only. Real jobs on a manual machine spend two to four times as long in setup, measuring and returning the carriage.
Tools for this job
The tooling this calculation is usually for, spread across the price range.
How does the cutting time calculator work?
Knowing the cut time tells you whether a power feed or a faster setup will actually save anything, and whether a job is worth a coolant setup. On hobby lathes most of the clock goes to measuring and resetting, not cutting.
Frequently asked questions
Why is my real job so much longer than the cutting time?
Manual machining is mostly setup, measuring, returning the carriage and changing tools. Two to four times the cutting time is normal. Power feed, a quick change tool post and a DRO cut that overhead more than a faster feed does.
Keep going
Formulas are standard shop math; starting speeds are conservative conventions for hobby machines. Not professional engineering advice. Wear eye protection and keep hands, gloves and sleeves clear of rotating work.