Definition
A workholding device used on a lathe that combines the features of an independent chuck and a universal (self-centering) chuck. Its jaws can be moved together by a single scroll mechanism for quick centering of round work, or moved individually to grip irregular or off-center work. It is used in machine shop operations such as those performed during aircraft component manufacture and repair.
Plain English
A clamping device on a lathe that holds a piece of metal while it spins. It can either tighten all its jaws at once to center a round part quickly, or let you move each jaw separately to hold odd-shaped parts.
Context Anchor
Seen in aircraft maintenance and machine-shop work, especially when a part must be held securely on a lathe before machining.
Derivation
Combination indicates the tool combines two functions in one device. Chuck comes from an old English word meaning a block or lump, later applied to mechanical clamps that hold a workpiece or tool firmly in place.
Why Pilots Care
Pilots usually do not use a combination chuck in flight, but the term can appear in maintenance material. Correctly holding a part during machining helps prevent inaccurate or damaged aircraft parts.
Intuition Check
Do not read “chuck” as “throw” here. In this context, a chuck is a device that grips and holds a part.
Example Sentence 1
The mechanic mounted the steel rod in the combination chuck and used the scroll feature to center it quickly before turning.
Example Sentence 2
After switching to a straight-shank bit, the technician left the same combination chuck on the drill press.