MODULE 02
Face, peripheral and contour milling. Feeds, speeds and workholding setups.
Overview
Milling is a machining process where a rotating multi-tooth cutter removes material from a stationary (or moving) workpiece. Unlike turning, the cutter rotates and the table feeds the part beneath it, enabling the production of flat surfaces, slots, pockets, contours, and complex 3D profiles.
Milling centers range from simple 3-axis vertical machining centers (VMC) to 5-axis simultaneous machines capable of producing turbine blades and medical implants in a single setup.
Types
Face Milling
Flat surfaces perpendicular to the cutter axis. Large-diameter face mills for broad stock removal.
Peripheral Milling
Cutting with the side of the cutter. Produces slots, steps, and side profiles.
Pocket Milling
Clearing enclosed cavities using ramping, helical, or plunge entry strategies.
Contour Milling
Following a 2D or 3D profile with ball-nose or bull-nose end mills.
Slot Milling
Full-width slot cut using slotting cutters or end mills. Careful chip evacuation required.
Thread Milling
Helical interpolation with a thread mill. One tool for many thread sizes; works in any material.
Parameters
Milling parameters involve the feed per tooth (fz) — how much material each cutting edge removes per revolution — along with spindle speed and width/depth of cut. Correct fz prevents rubbing (too low) or overload (too high).
Climb milling (cutter rotation matches feed direction) gives better finish and longer tool life. Conventional milling is safer when the machine has backlash. Modern CNC machines default to climb milling.
Workholding
Secure workholding is critical in milling — cutting forces act in multiple directions. The 3-2-1 locating principle constrains all six degrees of freedom: three points on the primary datum face, two on the secondary, one on the tertiary. Common solutions include machine vises, angle plates, modular fixtures, and vacuum chucks for thin plates.
G54–G59 work offsets in CNC allow multiple fixtures on one table, each with its own coordinate origin — eliminating re-homing between parts.
Tooling
End Mill
2–6 flutes. Fewer flutes for aluminum (chip clearance); more flutes for steel (rigidity).
Face Mill
Indexable inserts on large body. High MRR on flat surfaces. Economical insert replacement.
Ball-Nose
Hemispherical tip for 3D contours and smooth ramp cuts in mold and die work.
Drill / Interpolate
Helical interpolation with an end mill can replace a drill for flexible hole sizing.
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