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CNC

Basics of the CNC Mill 212

Basics of the CNC Mill explains the components and function of CNC mills. A CNC mill produces flat or curved surfaces on square or rectangular workpieces. CNC mills may have a vertical spindle or a horizontal spindle and either their table or cutting tool may move to execute a cutting operation. CNC mills use a variety of tools, which are kept in the toolchanger on a toolholder, to perform different cutting operations. The spindle grabs the toolholder and secures it. On the worktable, vises or fixtures may secure workpieces during machining. The CNC mill can perform multiple operations in the same setup.

It is essential for a CNC mill operator to be familiar with machine basics prior to executing any cutting operation. A trained operator can use a CNC mill to create precise parts safely and consistently. After taking this class, users should be able to describe the general machine components of a CNC mill and their basic function.

Difficulty Intermediate
Format Online
Number of Lessons 16
Language English

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Mills
Types of CNC Mill
CNC Mill Components
CNC Mill Movements
CNC Mill Component Review
Cutting Variables
Milling Cutters
Milling Operations
Holemaking Operations
Cutting Tool Materials
CNC Mill Operations
Toolholders for the CNC Mill
Toolchangers for the CNC Mill
Toolchanging and Milling Operations
Workholding for the CNC Mill
CNC Mill Review

Describe the mill.
Distinguish between the two types of CNC mills.
Identify components of the CNC mill.
Explain how the CNC mill moves to cut workpieces.
Identify the three primary cutting variables.
Describe common milling cutters.
Describe common milling operations.
Describe the capabilities of a CNC machining center.
Describe cutting tool materials for the CNC mill.
Identify components of a standard toolholder used on the CNC mill.
Describe the purpose of a toolchanger on the CNC mill.
Describe workholders used on the CNC mill.

Vocabulary Term

Definition

axial

A direction that runs straight along or parallel to the rotational axis of the cutting tool. The bottom of a tool makes axial cuts.

ballscrew

A long, threaded device that rotates to move the worktable or cutting tool of a CNC machine. Ballscrews are powered by a motor.

boring

The process of enlarging an existing hole with a single-point tool. Boring can be performed on a mill or machining center.

carbide

A common cutting tool material that is used to make both indexable inserts and solid cutting tools. Carbide is very hard and wear resistant.

CNC mill

A machine tool that uses computer numerical data to control cutting operations on flat, square, or rectangular workpieces. On a CNC mill, the cutting tool rotates against a workpiece that is fixed to a worktable.

column

The vertical support of a milling machine. The column suspends components and tools over the workpiece.

computer numerical control

CNC. A self-contained system of computers and precision motors that executes program instructions to guide machine tool components and manufacture parts. Mills often operate using computer numerical control.

contour

A curved surface or dimension that is cut into a workpiece. Contours are generally created using an end mill.

cutting variable

A factor that affects how a cutting tool performs its job. Cutting variables include speed, feed, and depth of cut.

depth of cut

The depth that the cutting tool penetrates the surface of the workpiece. On a mill, depth of cut is dictated by the movement of either the spindle or the worktable.

drilling

The use of a multi-point tool to machine a new round hole into the surface of a workpiece. Drilling is a type of holemaking operation.

end mill

A type of milling cutter that performs a mix of peripheral and face milling with its bottom and side cutting edges. End mills can be used to machine grooves, slots, circular slots, pockets, and contours.

face mill

A type of mill cutter that contains multiple teeth surrounding its large body diameter. The face mill uses the bottom as a cutting surface to mill large flat surfaces.

face milling

A milling operation in which the surface of the workpiece is perpendicular to the spindle axis. Face milling primarily cuts with the bottom of the cutting tool.

feed

The rate at which the cutting tool and the workpiece move in relation to one another. Feed is typically a linear movement but can also be angular and circular.

fixture

A custom workholding device that is designed to effectively support, locate, and hold a specific type of workpiece. A workpiece with multiple, complex dimensions often requires a dedicated fixture.

fixtures

A customized workholding device used to position and hold a part during various machining operations. Fixtures are built to hold a specific part design.

flange

A ring or collar surrounding the toolholder. Flanges allow a tool to be grasped by the toolchanger arm.

helix

A spiral shape. An end mill has cutting edges along its sides in a helix.

high-speed steel

HSS. A category of tool steels used for cutting tool applications. HSS is a tough but inexpensive material.

holemaking

The act of machining a hole into the interior surface of a workpiece. Holemaking can be accomplished by drilling, boring, reaming, and tapping.

horizontal mill

A mill with a spindle that is parallel to the worktable. The horizontal mill is less common than the vertical mill.

inches per minute

ipm. A unit of measurement that indicates how far in inches a tool advances in one minute. Inches per minute is used to measure feed.

inches per revolution

ipr. A unit of measurement that indicates how far in inches a tool advances in one rotation. Inches per revolution is used to measure feed.

index

To rotate a cutting head from one fixed position to another fixed position in order to reveal a fresh cutting edge. A cutting tool with multiple cutting edges should be indexed once the original edge has been worn or damaged.

inserts

A replaceable bit that has multiple cutting edges. Inserts can be indexed to a new cutting edge as each edge wears out.

intermittent cutting

A cutting process in which the cutting edge of the tool comes into and out of contact with the workpiece surface. Intermittent cutting is also known as interrupted cutting.

interrupted cutting

A cutting process in which the cutting edge of the tool comes into and out of contact with the workpiece surface. Interrupted cutting is also known as intermittent cutting.

machine control unit

MCU. A computer that controls and operates a CNC machine. Machine control units interpret the numerical data in the part program to guide machine movement.

machining center

A sophisticated CNC mill that can perform multiple machining operations in the same setup. Machining centers can hold a wide variety of cutting tools, including mills and holemaking tools.

machining centers

A sophisticated CNC mill that can perform multiple machining operations in the same setup. Machining centers can hold a wide variety of cutting tools, including mills and holemaking tools.

mill

A multi-point cutting tool that has teeth around its cutting surface. The term "mill" is also used to describe the machine tool that uses this multi-point cutting tool to remove material from the surface of a workpiece.

millimeters per minute

mm/min. A unit of measurement that indicates how far in millimeters a tool advances in one minute. Millimeters per minute is used to measure feed.

millimeters per revolution

mm/rev. A unit of measurement that indicates how far in millimeters a tool advances in one rotation. Millimeters per revolution is used to measure feed.

milling machine

A machine that uses a rotating multi-point tool to remove material from the surface of a workpiece. Milling machines are commonly used to machine slots, grooves, and flat surfaces on rectangular workpieces.

multi-point tool

A cutting tool with more than one cutting edge. Multi-point tools include mills and drills.

pallet

An automatic, moveable table that supports a workpiece and slides or pivots into and out of the CNC mill. Pallets allow an operator to set up a part while another is being machined.

parallel

Two lines that are equidistant from one another and do not intersect. On a CNC mill, a cutting tool can be positioned parallel to the workpiece.

part program

A series of alphanumerical instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific workpiece. Multiple part programs can be stored in a CNC at one time.

peripheral milling

A milling operation in which the cutting edge of the mill is parallel to the axis of rotation. Peripheral milling primarily cuts with the side edges of the cutting tool.

perpendicular

Two lines or axes that intersect to form a right angle. On a CNC mill, a cutting tool can be positioned perpendicular to the workpiece.

pocket

An interior recess that is cut into the surface of a workpiece. Pockets may be round or rectangular and generally are created using an end mill.

pots

One of the numerous slots of the toolchanger that holds a cutting tool in its toolholder. Each pot has a specific location number.

radial

A direction perpendicular to the tool rotational axis commonly called the radius of the tool. The periphery of a tool makes radial cuts.

ramped

A tool movement that gradually engages the cutting tool with the workpiece. A ramped face mill can cut a pocket without the existence of a premachined cavity in the workpiece.

reaming

The process of enlarging or smoothing an existing hole with a multi-point tool. Reaming is a holemaking operation.

retention knob

A knob screwed into the end of the toolholder. Retention knobs lock a tool in place within the spindle.

servomotors

A motor in a CNC machine that powers the movement of the machine tool. Servomotors rotate ballscrews, which cause a machine component to move.

slot

A narrow channel cut into the surface of a workpiece. Slots can be created with either a face or end mill.

speed

The rate at which the machine spindle rotates. The spindle speed affects how fast the cutting tool moves at the point of contact.

spindle

The part of the machine tool that spins or rotates. On the mill, the spindle holds the cutting tool.

tapered shank

The long, narrow portion of a toolholder that is typically shaped like a cone. Tapered shanks are the most common shape for a mill toolholder.

tapping

The process of cutting internal threads in a hole with a rotating multi-point tool. Tapping can be performed on a mill or machining center.

toolchanger

A milling machine device that arranges and positions multiple cutting tools for the spindle to retrieve. The toolchanger also stores the cutting tools between uses.

toolholder

A mechanism used to rigidly hold a cutting tool in place during machining. Toolholders are classified so that they can be paired with the correct style of cutting tool or insert.

vertical mill

A mill with a spindle that is perpendicular to the worktable. Vertical mill worktables are parallel to the ground.

vise

A workholding device with two jaws that grip and hold a workpiece in place. Vises are mostly used to hold rectangular workpieces with fairly simple dimensions.

workholding

The process of securely supporting, locating, and clamping a workpiece for a manufacturing operation. Workholding devices for CNC mills and machining centers hold the workpiece in place on the worktable.

workpiece

A part that is in the process of being manufactured. A workpiece may be a complete product by itself or one component of a product consisting of many parts.

worktable

The component of a milling machine that supports the workpiece and any workholding device during machining. The worktable moves along the X and Y axes.