Manual Mill Basics 201

adjustable boring head

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

angle vise

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

arbor

The bar attached to the spindle of a horizontal milling machine. The arbor holds the milling cutter 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.

belt

An endless loop of material used to transmit motion between two or more pulleys. Belts on a milling machine motor should only be repositioned with the spindle turned off.

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

Two parallel box-shaped rails that guide movement of a machine component. Box ways help keep the mill table aligned to the knee as it moves and are also referred to as square ways.

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.

collet

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 whose spindle is mounted in the column, and whose worktable rests on an adjustable knee. Column and knee milling machines are the most common type of manual mill.

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.

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.

dovetail cutters

A mill cutter used to cut a dovetail angle into a workpiece. Dovetail cutters can produce angled slots.

dovetail ways

Two parallel angle-shaped rails that guide movement of a machine component. Dovetail ways help to keep the mill table 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

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

drill chuck

A type of toolholder that holds drill bits on the mill. Drill chucks allow for 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.

end mill

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

end mill toolholder

A toolholder that holds an end mill in place with a setscrew. End mill toolholders hold tools with more rigidity than collet-type toolholders.

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 cutter 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 milling

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

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.

forward-reverse switch

The main directional control for the spindle that determines whether the spindle rotates forward or reverse. The forward-reverse switch is also known as the high-low range switch.

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.

gear

A round or cylindrical mechanical component with teeth that is used to transmit power. Gears are designed to mesh with one another and can alter the speed, torque, or direction of mechanical energy.

gibb

A device used to reduce side play in the mill table as it is moved from one direction to another. Gibbs are placed between the ways and the table.

half-side cutters

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

head

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

helical

Winding in the shape of a spiral or coil. Helical flutes appear on drills and end mills.

hex bolt

A type of bolt that has a head with six sides. Hex bolts are used to tighten drawbars.

hi-neutral-lo lever

The control that puts the motor in gear. The hi-neutral-lo lever, located on the right side of the mill head, is tied to the operation of the forward-reverse switch.

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 are less common than vertical column and knee milling machines.

indexable

Having multiple cutting edges than can be repositioned to reveal a fresh cutting edge. Indexable inserts on a face mill can be rotated to a different cutting edge once the original edge has been worn or damaged.

inserts

A cutting tool that has multiple usable cutting edges. Inserts are typically very hard and wear resistant.

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.

jaw

A component on a vise that grips and holds the workpiece in place. Jaws of a vise used in a milling operation are adjustable.

knee

The device that supports the mill worktable from underneath. The knee can be used to adjust the worktable to different heights.

knee crank

A handle used to raise and lower the knee and worktable on a milling machine. The knee crank features a micrometer that allows operators to adjust the feed rate incrementally.

locknut

A nut that is used to keep the micrometer adjustment nut from moving out of position. The locknut is located below the micrometer adjustment nut.

manual feed handwheel

A handwheel located on the front of the mill head that controls quill feed. The manual feed handwheel is used for very precise quill movements.

manual mills

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

micrometer

A measuring instrument with a threaded spindle that slowly advances toward a small anvil. Micrometers are available in numerous types for measuring assorted dimensions and features.

micrometer adjustment nut

A nut located on a threaded rod that is used to determine spindle depth. The micrometer adjustment nut on a mill head is numbered in thousandths of an inch or hundredths of a millimeter.

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.

mills

A rotating, multi-point cutting tool that is guided along a workpiece to remove metal. Milling machines may also be referred to as mills.

motor

A machine that converts one form of energy, such as electricity, into mechanical energy or motion. The motor on a mill head powers a belt and pulley system, which then rotates the spindle.

multi-point tool

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

overarm

The part of the horizontal milling machine that reaches over the workpiece and worktable. The overarm supports the spindle and arbor.

parallel

Two lines 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

Two rectangular strips or blocks of precision metal that help support the workpiece in the vise. Parallels allow for raising the workpiece to the desired working height in the vise.

perpendicular

Meeting at a right angle. On a vertical mill, the spindle is perpendicular to the worktable.

personal protective equipment

PPE. Any of the various articles of clothing or safeguarding devices that assemblers or operators are required to wear to ensure their safety. Personal protective equipment for a milling operation includes safety glasses.

power feed

The method of moving a workpiece or machine component automatically. Power feed on a mill is turned on with the power feed engagement crank and adjusted by the quill feed selector.

power feed engagement crank

A switch that sets the quill feed to run automatically. The power feed engagement crank turns the power feed on, while the quill feed selector adjusts automated feed rates.

power feed unit

A control unit that allows the table to move side to side automatically. The power feed unit is attached to the mill table and must first be set by an operator.

powered drawbars

A type of drawbar that automatically pulls the toolholder into a secure position. Powered drawbars are typically controlled by a switch mounted on the machine.

pulley system

A setup on a machine consisting of two round, fixed pulleys. A pulley system features one pulley that powers and moves a belt, which in turn moves the other pulley.

quick-change tooling

A toolholding system that uses a master toolholder with a set of interchangeable toolholders. Quick-change tooling increases the speed of production.

quill

A shaft that moves the spindle in and out of the mill head. The quill feed handle controls the quill's main vertical movements, while the manual feed handwheel allows for smaller, more precise movements.

quill

The component on the mill that moves the spindle in and out of the mill head. The quill feed can be controlled manually or automatically.

quill feed handle

The main lever used to manually move the quill. The quill feed handle is located on the lower right side of the mill head and controls the quill feed.

quill feed selector

The knob on the left side of the mill head that allows the operator to set the automatic feed rate for the quill. The quill feed selector has three feed settings, which are small fractions of an inch or millimeter.

retrofit

To modify a machine or tool with a new part. Retrofitting manual mills with quick-change tooling reduces 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 characterized as stiff and immoveable. Rigid components are fixed securely in place.

rotary bases

A rotating base on the bottom of the vise. Rotary bases can position the workpiece at a variety of angles to the X and Y axes.

saddle

A machine component that moves the worktable back and forth from the column. The saddle on a column and knee 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 with end mill toolholders.

shell mill

A milling cutter with solid, nonindexable cutting edges around its entire periphery. A shell mill's cutting edges are often helical, similar to an end mill.

slab milling

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

slotting

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

speed change handwheel

A variable speed control handle that allows the operator to adjust spindle speed. The speed change handwheel on a mill adjusts spindle speeds incrementally within two speed ranges: high or low.

spindle

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

spindle depth

The distance inside the workpiece that the spindle reaches during a cutting operation. Spindle depth is controlled by setting the micrometer adjustment nut or using the knee crank.

spindle feed

The rate at which the spindle moves in and out of the mill head. The spindle feed is controlled by the quill feed handle or the manual feed handwheel.

spindle speed

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

square ways

Two parallel square rails that guide movement of a machine component. Square ways help keep the mill table aligned to the knee as it moves and are also referred to as box ways.

stop rods

Control devices used to limit the travel of the table automated by the power feed unit. The stop rods are located on the front of the mill table.

straddle milling

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

thread stripping

A condition in which a screw has damaged threads as a result of overtightening. Thread stripping can occur when tightening a mill's drawbar manually.

toolholders

The device used to rigidly hold a cutting tool in place. Toolholders may hold inserts or larger tools.

T-slot cutters

A T-shaped milling cutter 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-slotting

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

variable speed control

A speed control on the mill with a high and low speed range. Speeds can be set to any speed within the high and low speed range.

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. Vises are often used to hold workpieces on the mill.

ways

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

workholding

A device used to hold and locate a workpiece. Workholding is used to keep the workpiece stationary on a mill.

worktable

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

X axis

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