Vise

A CNC vise is a precision workholding device with a fixed jaw and movable jaw used to locate and clamp a part on a mill. It establishes the primary datum by referencing the fixed jaw and base, then restrains the workpiece against cutting forces. Precision CNC vises are ground for flatness and parallelism, minimizing jaw lift to keep the part seated under clamping force.

On a CNC mill, the vise is the foundation of setup: the fixed jaw becomes the primary machine reference, so tramming it parallel to the table axis directly determines part squareness and position repeatability. High-end vises feature ground bases and side faces, allowing consistent mounting and indicating from multiple orientations. During production, clamping repeatability and parallelism are critical because any part movement under load translates into size errors, poor finish, or tool breakage. The vise also acts as a datuming system—its flat reference surfaces eliminate re-indicating for each batch, supporting fast changeovers. When machining thin stock, tall parts, or deep cuts, jaw-lift control becomes essential to maintain part seating and avoid dimensional drift. Proper vise selection and alignment directly affect batch-to-batch consistency, making it a cornerstone of efficient CNC workholding.

• ⚠️Jaw lift on tightening: If the movable jaw pulls the part upward as it closes, the workpiece seats inconsistently. This causes Z-height variation, tapered pockets, or out-of-parallel faces from stressed clamping.
• ⚠️Chips under the base or jaws: A trapped chip breaks the reference surface contact, shifting the effective datum. Parts machine “correctly” relative to a false setup, producing repeated offset errors and bad first articles.
• ⚠️Overclamping thin or soft material: Excessive torque deforms aluminum or plastics, especially with small contact area. The part measures in tolerance while clamped but springs back after release, creating size drift and warped flats.