Definition
A machining operation in which a small amount of material is removed from a workpiece on a lathe to produce a smooth, accurate final surface and bring the part to its specified dimensions and finish. It is the last cutting pass after rough turning, made with a light depth of cut, a fine feed rate, and a sharp tool to achieve the required surface quality and tolerance.
Plain English
The final, light cut taken on a lathe to clean up a part and bring it exactly to size with a smooth surface.
Context Anchor
Seen in aircraft maintenance, repair, and machine-shop work when metal parts are being made or restored.
Derivation
‘Finish’ comes from the Latin ‘finis,’ meaning end or boundary. ‘Turning’ refers to shaping a part while it rotates (turns) on a lathe. So ‘finish turning’ literally means the ending turn — the last lathe cut that finalises the part’s size and surface.
Why Pilots Care
A part that is not finish turned correctly may fit poorly, wear faster, or fail to meet the repair requirements for the aircraft.
Analogy
Think of sanding wood: rough sanding shapes it, fine sanding makes it smooth and ready to use. Finish turning is the fine-sanding stage of lathe work.
Intuition Check
Finish turning does not mean completing a turn in flight. In this maintenance context, turning means cutting a rotating part, and finish means making the final accurate pass.
Example Sentence 1
After rough turning the shaft to within a few thousandths of an inch of size, the machinist performed finish turning to bring it to the exact diameter called out on the drawing.
Example Sentence 2
Finish turning cleanly on the downwind leg to avoid overshooting the runway heading.