A second pass with no change in dial setting, taken because the tool and work deflected under load on the first pass and left material behind. It is routine in single-point threading, boring with long bars and turning slender parts. The spring pass usually takes off a few tenths to a thou and improves size consistency and finish.
Take a spring pass on that thread before you check it, the bar was pushing off on the last cut.
Also heard as
- spring cut
Do not mix it up with
- Skim cut: A skim cut takes a deliberately light depth to clean a surface; a spring pass repeats the last setting with no added depth.
Related terms
Skim cut
A very light cut that just cleans up a surface or establishes size without removing much material.
Sneak up on it
Approach a final dimension with smaller and smaller cuts, measuring between each, so you never go undersize.
Single-point
To cut a thread on a lathe with a single-point tool over several passes, rather than with a die or tap.
Kentucky windage
Adjusting by experience and feel rather than by the numbers, borrowed from riflemen aiming off for wind.