CNC Work Holding & Fixturing 3

Question 1

What is the function of a floating jaw (compensating jaw) in a CNC vise?

Accepted Answer

To self-adjust and distribute clamping force evenly on non-parallel workpiece faces

Answer

A floating or compensating jaw pivots slightly to make full contact with both sides of a non-parallel or irregular workpiece, preventing rocking.

Question 2

A cam-lock fixture is characterized by its ability to:

Accepted Answer

Quickly clamp and release a workpiece with a 90-degree handle rotation

Answer

Cam-lock clamps convert a partial rotation of a cam into a secure clamping action, enabling fast loading and unloading of workpieces.

Question 3

When a workpiece is clamped in a four-jaw independent lathe chuck on a CNC turning center, the primary advantage over a three-jaw chuck is:

Accepted Answer

The ability to indicate and center non-round or eccentric workpieces

Answer

Each jaw of a four-jaw chuck adjusts independently, allowing precise centering of irregular parts or intentional eccentricity.

Question 4

What is the purpose of a fixture plate (also called a sub-plate or tooling plate)?

Accepted Answer

To provide a repeatable, pre-drilled mounting surface for quick fixture changes

Answer

A tooling plate with precision-bored holes and threaded inserts allows fixtures and clamps to be mounted quickly and repositioned accurately.

Question 5

In CNC milling, workpiece 'lift-off' during a climb milling pass is most commonly prevented by:

Accepted Answer

Ensuring clamps are positioned over the supported areas of the workpiece

Answer

Positioning clamps directly over the support points (parallels, stop pins) counters the upward cutting force and prevents part lifting.

(CNC) Computer Numerical Control Machinist Technical Practice Test