Manual Mill Basics 201

adjustable boring head

A toolholder used in boring operations that require a hole diameter larger than that of the boring tool. An adjustable boring head can be set to bore differently sized hole diameters.

angle vises

A type of vise that can position the workpiece at an angle. Angle vises can be adjusted from zero to 90 degrees.

arbor

A bar attached to the spindle of a horizontal milling machine. The arbor holds the milling cutting tool for different types of milling processes.

base

The foundation of a machine that supports all the other machine components. The base of a milling machine is typically square or rectangular.

boring

The process of enlarging an existing hole with a single-point tool. Boring removes small amounts of material to achieve tight tolerances and finishes.

box ways

A pair of parallel, square rails that guides movement of a machine component. Box ways, or square ways, help keep the mill worktable aligned to the knee as it moves.

carbide

A common cutting tool material used to make both indexable inserts and solid cutting tools. Carbide tools are hard and wear resistant when used under optimal milling conditions.

chips

A piece of metal that is removed from a workpiece during cutting or grinding. Chips are tiny curls, shards, fragments, or particles of metal.

collets

A split-sleeve device that expands or contracts to grip a cutting tool as it rotates. Collets come in various sizes to match specific tool diameters.

column

The vertical support, or backbone, of a milling machine. The column is supported by the machine base.

column and knee milling machine

A milling machine with a spindle mounted to the column and a worktable that rests on an adjustable knee. Column and knee milling machines are the most common type of manual mill and are available in vertical or horizontal orientations.

contours

A curved, non-linear dimension created by a cutting process. Contours can be created by precise tool movements in milling.

cutting

The use of single- or multi-point tools to separate metal from a workpiece in the form of chips. Cutting processes vary based on the requirements of a finished part.

cutting tool

A device made of hard, tough material that is used to remove metal by creating chips. Cutting tools are either single or multi-point tools.

depth of cut

The amount of material removed by one pass of the cutting tool. Depth of cut measures how far the cutting tool penetrates the surface of the workpiece during a cut.

diameter

The distance from one edge of a circle to the opposite edge that passes through the center. Diameter measurements are required for round or cylindrical features.

dovetail cutters

A mill cutting tool used to produce angled slots. Dovetail cutters create very strong slots or grooves that are often used for fixtures or joints.

dovetail ways

A pair of parallel, angle-shaped rails that guides movement of a machine component. Dovetail ways help to keep the mill worktable aligned to the knee as it moves.

drawbar

A long metal bar that is threaded through the spindle and pulls the toolholder into a seated position. Drawbars can be manual or powered.

drill chuck

A type of toolholder that holds drill bits on the mill. Drill chucks enable quick installation and removal of drill bits.

drill press

A machine tool that can be used for a variety of holemaking operations. Drill presses create round holes in workpieces.

drills

A multi-point cutting tool used to make round holes. Drills generally have two flutes and a pointed end.

end mill

A mill cutting tool used to machine grooves, slots, pockets, and contours into workpieces. End mills have one or more flutes.

end milling

A milling operation that uses a narrow mill to create pockets, slots, and contours in a workpiece. End milling may cut with both the bottom and sides of the cutting tool.

face mill

A flat mill cutting tool with multiple cutting teeth surrounding the bottom edge. The face mill is often used to remove a large amount of material to create flat surfaces.

face mill assemblies

A manual mill component that includes a face mill cutting tool and a conical toolholder in one setup. The toolholder of a face mill assembly may also be called a face mill arbor.

face milling

A milling operation that produces a flat surface. Face milling is primarily used on the top surface of a workpiece.

fixed spindles

A design of manual mills that allows the spindle to rotate in place but not travel from side-to-side or in-and-out of a workpiece. Fixed spindles are more common on horizontal mills.

flute

A straight or helical recessed feature on the periphery of a cutter. Flutes allow chips to flow away from the cut.

form milling

A milling operation that uses a mill with a unique shape to create that shape into the workpiece. Form milling is often used to machine gears and other parts requiring specially contoured shapes.

full-side cutters

A narrow, wheel-shaped milling cutter with teeth on both sides of its periphery. Full-side milling cutters are used on horizontal mills to create vertical workpiece features.

gib

A device used to reduce undesired worktable movement in the mill table as it is moved from one direction to another in a mill. A gib is placed between the ways and the table.

half-side cutters

A narrow, wheel-shaped mill cutting tool that has teeth on one side of its periphery. Half-side cutters are used on horizontal mills to create vertical workpiece features.

head

A part of a vertical milling machine that holds the spindle. The head usually also contains various speed and feed controls for the mill.

helical

A winding shape in a spiral or coil. Helical flutes appear on drills and end mill cutting tools.

hex bolt

A type of bolt that has a six-sided head. Hex bolts are used to tighten drawbars on manual mills.

holemaking

A machining operation in which a single- or multi-point cutting tool creates, sizes, or finishes a hole. Holemaking includes drilling, boring, reaming, and tapping.

horizontal column and knee milling machine

A milling machine with a spindle that is parallel to the ground and machine worktable. Horizontal column and knee milling machines, or horizontal mills, are less common than vertical column and knee milling machines.

indexable carbide inserts

A cutting bit that has multiple cutting edges made out of strong, carbide steel. Indexable carbide inserts can be replaced or changed to a new cutting edge after excessive wear or damage.

indexable toolholders

A component designed to hold multiple toolholders at once. Indexable toolholders allow different cutting tools to be rotated into place without changing the tooling or setup of a machine.

interrupted cutting

A machining 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.

jaw

A component on a vise that grips and holds the workpiece in place. Jaws of vises are usually adjustable.

knee

A component of a mill that supports the worktable from underneath. The knee can be used to adjust the worktable vertically and, sometimes, horizontally.

manual mill

A machine controlled by an operator that uses a multi-point cutting tool to remove metal from the surface of a workpiece. Manual mills are classified as either vertical or horizontal based on their spindle orientation.

micrometer adjustment screw

A threaded rod that is used to make fine changes to spindle depth on a manual mill. The micrometer adjustment screw enables precise changes in thousandths of an inch or hundredths of a millimeter.

milling

A cutting operation in which a rotating multi-point cutting tool is fed along a part's surface to remove material. Milling operations are very versatile and generally produce flat surfaces.

milling machine

A machine that uses a multi-point tool to remove metal from the surface of a workpiece. Milling machines are also called mills.

multi-point tool

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

overarm

A component of a horizontal milling machine that extends over the workpiece and worktable. The overarm supports the spindle and arbor.

parallel

A set of lines, components, or axes that are equidistant from each other at all points along their length and thus never intersect. On a horizontal mill, the spindle is parallel to the worktable.

parallels

A pair of rectangular strips or blocks of precision metal that help support the workpiece in a vise. Parallels can be used to raise the workpiece to a desired working height in a vise.

perpendicular

A set of lines, components, or axes that meet at a right angle. On a vertical mill, the spindle is perpendicular to the worktable.

pockets

An enclosed recess that is machined into the surface of a workpiece. Pockets are usually square or rectangular with rounded corners.

power feed

A system that enables automatic movements of a workpiece or machine component. Power feed systems on some manual mills automatically move the quill to adjust the depth of cut.

power feed unit

A control unit on some manual mills that enables automatic movement in the worktable. A power feed unit can automatically adjust the worktable vertically and, sometimes, horizontally.

quick-change tooling

A toolholding system that uses a master toolholder with a set of interchangeable toolholders or cutting tools. Quick-change tooling increases production speeds for manual milling processes.

quill

A component on some manual mills that moves the spindle in and out of the mill head. The quill can be controlled automatically or manually, such as with a lever or handwheel, to adjust spindle depth.

retrofitted

A modernizing or upgrading process that adds features with which a machine was not originally manufactured. Retrofitted manual mills may be upgraded with quick-change tooling to reduce the time spent changing toolholders.

revolutions per minute

rpm. A measurement of speed that tracks how many times a machine component rotates in one minute. Revolutions per minute measures the spindle speed on a milling machine.

rigidity

The condition of a workpiece, machine, or machine setup that is characterized as stiff and immoveable. Rigid components are inflexible and fixed securely in place.

rotary bases

A rotating base on the bottom of a vise. Rotary bases can position a workpiece at a variety of angles relative to the spindle.

saddle

A machine component that moves the worktable back and forth relative to the column. The saddle on a column and knee milling machine rests on the knee.

setscrew

A type of screw, often with no head, used to hold a device in place relative to other components. Setscrews are used as toolholders for end mill cutting tools.

shell mill

A mill cutting tool with solid, non-indexable cutting edges around its entire periphery. A shell mill's cutting edges are often helical like the flutes on an end mill or drill.

slab milling

A milling operation that uses a cylindrical cutting tool on an axis parallel to the worktable to create a flat surface. Slab milling is performed on horizontal mills.

slots

A rectangular channel cut into the surface of a workpiece. Slots are created on mills during slotting operations.

slotting

A milling operation that cuts a long, rectangular channel into the surface of a workpiece. Slotting uses a disk-like cutting tool.

spindle

A component of a machine that rotates or spins. The spindle holds and rotates the cutting tool on a manual mill.

spindle depth

The distance inside the workpiece that the spindle reaches during a cutting operation. Spindle depth affects the depth of cut and varies based on factors like workpiece material and cutting speed.

spindle feed

The rate at which the spindle moves across the workpiece, measured in inches per revolution (IPR) or millimeters per revolution (mm/rev). Spindle feed can be adjusted automatically on some manual mills or manually with a lever, handwheel, or other control.

spindle speed

The rate at which the machine spindle rotates. Spindle speed is typically measured in revolutions per minute (rpm).

square ways

A pair of parallel, square rails that guides movement of a machine component. Square ways, or box ways, help keep the mill worktable aligned to the knee as it moves.

stop rods

A control device that limits the travel of the worktable. Stop rods are located on the front of a mill worktable.

straddle milling

A milling operation that uses two, parallel cutters attached to the arbor to create two identical, parallel, vertical workpiece features. Straddle milling is performed on a horizontal mill.

stripping

A condition in which a screw has damaged threads as a result of overtightening. Stripping can occur when manually tightening the drawbar on a manual mill.

table

A machine component that supports the workpiece and any workholding devices. The table, or worktable, on a manual mill moves side-to-side and back-and-forth.

threads

A long, spiral ridge around the exterior or interior of a cylindrically shaped object. Threads are used to fasten drawbars into manual mill heads.

toolholders

A device used to securely hold a cutting tool in place. Toolholders for the manual mill include set screws, collets, drill chucks, and face mil assemblies.

T-slot cutters

A mill cutting tool that machines a portion of a T-shaped slot into a workpiece. T-slot cutters often resemble a toothed disk mounted on a narrow arm.

T-slots

A T-shaped opening that runs the length of a worktable. T-slots enable machinists to clamp vises and other workholding components onto the worktable.

T-slotting

A milling operation that uses a T-shaped cutting tool to cut a channel shaped like an inverted T into a workpiece. T-slotting is often used to machine worktables.

vertical column and knee milling machine

A manual milling machine with a spindle that is perpendicular to the ground and machine worktable. Vertical column and knee milling machines are more common than horizontal mills.

vise

A workholding device with two jaws that grip and hold a workpiece in place. A vise is one of the most common workholding devices for the mill.

ways

A pair of parallel rails that guides the movement of a machine component. Ways keep the mill worktable straight and parallel to the knee as it moves.

workholding devices

A component used to secure, support, and locate a workpiece during a manufacturing operation. The most common workholding devices for the manual mill are vises.

workpiece

A part that is in the process of being machined. A workpiece may be subject to cutting, grinding, forming, welding, or other operations to produce a finished part.

worktable

A machine component that supports the workpiece and any workholding devices. The worktable, or table, on a manual mill moves side-to-side and back-and-forth.

X axis

An axis that represents linear motions and positions to the left or right of a mill operator. The X axis represents coordinates along the longest distance parallel to the worktable on a mill.