Work Holding & Fixturing Flashcards
7 cards from real CNC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Work Holding & Fixturing flashcards as text
What is a 'zero-point clamping system' (such as Erowa or System 3R) primarily designed to achieve?
Answer: Allow pallets and fixtures to be swapped with sub-micron repeatability
Zero-point systems use precision pull-down studs and locating bores to achieve pallet changes with repeatability typically under 0.005 mm, reducing setup time dramatically.
When indicating a round part held in a V-block, what characteristic of the V-block allows accurate centering?
Answer: The two angled faces locate the part at the same centerline regardless of diameter variation
A V-block's angled faces contact the part at two tangent points, automatically centering it on the block's axis regardless of slight diameter differences.
In the 3-2-1 locating principle, which surface receives the fewest locating points?
Answer: Tertiary datum — 1 point
The tertiary (third) locating surface requires only one point to constrain the final remaining degree of freedom.
A strap clamp set at an angle where the bolt end is lower than the workpiece end will:
Answer: Cause the clamp to shift toward the step block side
When the bolt is lower than the work end, the clamp tilts and the work side rises, reducing force on the part and allowing the clamp to slide toward the step block.
What material property makes aluminum the most common choice for soft vise jaws?
Answer: Easy machinability that allows quick profiling and low risk of marring workpieces
Aluminum machines quickly and cleanly, reduces setup time for profiling the jaws, and is soft enough to avoid marring finished surfaces on harder workpieces.
An expanding mandrel is used in CNC turning primarily to:
Answer: Locate and clamp a workpiece by expanding inside a pre-existing bore
An expanding mandrel is inserted into a bored hole in the part and then expanded outward to grip the bore ID, locating the part precisely on its own bore axis.
When specifying the clamping sequence on a complex fixture, what is the general rule regarding clamp application order?
Answer: Apply clamps in a sequence that does not distort the part — typically from the most rigid support outward
Clamping should progress from the primary datum outward, ensuring the part is seated on its locators before secondary clamps introduce distortion.