A code

A word in a part program that indicates tool angle during each pass of a threading operation. A codes are neccessary for G76 canned cycles.

bar stock

Raw material sold in the form of long bars. Bar stock can be round, square, or hexagonal.

block

A single line of a part program. Blocks are composed of words and written in G code programming.

boring

The process of enlarging an existing hole with a single-point tool. Boring is performed to improve the surface finish and concentricity of a hole.

canned cycles

A predetermined machining sequence used to simplify programming. A canned cycle sequence is initiated by a single G code.

castings

A workpiece formed by melting various raw materials, pouring them into a mold or cavity, and removing the workpiece once the materials have cooled and solidified. Castings are often similar to their desired final shape and require profile turning rather than straight turning operations.

centerline

An imaginary line that runs through the center of an object or divides a shape into two equal halves. The centerline is the axis along which a part rotates on a CNC lathe.

chamfers

An angled edge around the end of a cylindrical workpiece or the entrance of a hole. Chamfers can be machined using a multiple repetitive cycle.

chips

An unwanted piece of metal that is removed from a workpiece. Chips are formed when a tool cuts or grinds metal.

clearance plane

The safe distance for rapid tool movement from one operation to the next. A clearance plane is specified by an R level.

CNC lathes

A machine that uses computerized numerical data to control workpiece rotation and cutting tool movements for the machining of cylindrical parts. CNC lathes are precise and versatile.

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. CNC machines use part programs to control the cutting operations required to create a part.

concentricity

A geometric tolerance that ensures that the median points of a cylindrical feature are within a specified distance of the feature's sides. Concentricity of a hole improves when the hole is reamed or bored with the G85 canned cycle.

contours

A curved or complex shape on a workpiece surface. Contours can be machined using a multiple repetitive cycle.

counterboring

A holemaking operation that enlarges one end of a previously drilled hole to a certain depth. Counterboring allows room for the head of a screw or nut.

cutting fluid

Any fluid used to cool, lubricate, and clear chips during metal cutting. Cutting fluids may be composed of oils, water, synthetic fluids, or a combination of the three.

D code

A G code programming word that indicates the depth of cut in a rough turning and rough facing cycle. A D code indicates the number of tool passes in the G73 rough profile turning cycle.

depth

The top-to-bottom measurement of a recess or relief. For a thread, the depth is the distance between the root and the crest, indicated by the K code in a G76 threading canned cycle.

depth of cut

doc. The distance that a cutting tool penetrates the surface of a workpiece. Depth of cut determines the amount of material removed with each cutting pass.

diameter

The distance from one edge of a circle to the opposite edge through the center. A drill's diameter is the thickness of the drill.

drag line

A mark left along the length of a hole at the end of a G86 rough boring operation. Drag lines are the result of a boring tool retracting rapidly out of a hole.

drilling

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

dwell

A pause built into the execution of a program in which the cutting tool remains in contact with the workpiece. A dwell can be used to improve the finish of a hole.

F code

A word in a part program that determines the feed rate during a cutting operation. F codes are usually given in inches per minute or inches per revolution.

facing

A lathe cutting operation that feeds a cutting tool across an end of a cylindrical workpiece to create a flat surface and shorten its length. Facing can be performed with the G94 canned cycle.

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.

feed rate

The rate at which the cutting tool moves along the workpiece. Feed rate is typically a linear movement.

finishing

A final metal cutting pass that emphasizes tight tolerances and smooth surface finish. Finishing cuts usually follow roughing operations.

forgings

A workpiece formed by compressing or hammering hot metal to achieve a specific shape. Forgings are often similar to their desired final shape and require profile turning rather than straight turning operations.

G code

A word in a part program that determines the type of operation performed on the CNC machine. G codes apply to all blocks following their occurrence until a new G code occurs in the part program.

G code programming

A method of programming that pairs address letters with numerical values to form words. G code programming is used to write a part program.

G70

A code in G code programming that generally activates the finish turning or facing canned cycle. The G70 canned cycle follows either a G71, G72, or G73 canned cycle.

G71

A code in G code programming that generally activates the rough turning canned cycle. The G71 canned cycle is a multiple repetitive cycle.

G72

A code in G code programming that generally activates the rough facing canned cycle. The G72 canned cycle is a multiple repetitive cycle.

G74

A code in G code programming that generally activates the left-hand tapping canned cycle. During the G74 canned cycle, the cutting tool rotates counterclockwise as it enters a hole to cut a thread.

G76

A code in G code programming that generally activates the threading canned cycle. The G76 canned cycle machines a thread on a part using a series of progressively smaller cuts at a specified angle.

G81

A code in G code programming that usually activates the general drilling canned cycle. During the G81 canned cycle, the cutting tool positions to a hole location, drills a hole, and then exits out of the hole.

G82

A code in G code programming that generally activates the drilling with dwell canned cycle. During the G82 canned cycle, the cutting tool remains in position at the bottom of a hole before retracting out of it.

G83

A code in G code programming that generally activates the standard peck drilling canned cycle. During the G83 canned cycle, the cutting tool moves rapidly out of the hole between pecks.

G84

A code in G code programming that generally activates the right-hand tapping canned cycle. During the G84 canned cycle, the cutting tool rotates clockwise as it enters a hole to cut a thread.

G85

A code in G code programming that generally activates the boring/reaming canned cycle. The G85 canned cycle feeds a cutting tool into and then back out of a hole at the same feed rate without stopping when reversing direction at the bottom of the hole.

G86

A code in G code programming that generally activates the rough boring canned cycle. In the G86 canned cycle, a boring tool feeds into a hole, stops at the bottom, and then moves rapidly back out of the hole.

G90

A code in G code programming that generally activates the turning canned cycle. The G90 canned cycle can be used to perform a straight or tapered cut parallel to the Z axis.

G94

A code in G code programming that generally activates the facing canned cycle. The G94 canned cycle makes a straight or tapered cut parallel to the X axis.

G98

A code in G code programming that instructs the cutting tool to return to the initial level. G98 codes are often used at the end of canned cycles.

G99

A code in G code programming that instructs the cutting tool to return to the R level or clearance plane. G99 codes are often used at the end of canned cycles.

holemaking

The act of machining a hole into the surface of a workpiece. Holemaking operations include drilling, boring, reaming, and tapping.

I code

A word in a part program that indicates the initial amount of material to be removed along the X axis. I codes are required for a G73 rough profile turning canned cycle.

initial level

The X axis or Z axis tool position when a canned cycle is initiated. The initial level is typically located above the R level.

initial level return

A movement that positions the cutting tool at the initial level at the end of a canned cycle. Initial level return occurs when a G98 code is used in a part program.

K code

A word in a part program that indicates the initial amount of material to be removed along the Z axis. K codes are required for a G73 rough profile turning canned cycle and G76 threading canned cycle, when the K code indicates the depth of thread per side.

lead

The distance a cylinder travels in one revolution. Leads are created by the feed rate set by the F code in a G76 threading canned cycle.

left-hand tap

A cutting tool that rotates counterclockwise as it enters a hole to cut a thread. Left-hand taps require the use of the tapping canned cycle G74.

live tooling

Power-driven tools, such as end mills and drills, that are installed in a CNC lathe turret. Live tooling can perform cutting operations off-center while the workpiece is held still in the spindle.

machine control unit

MCU. A small, powerful computer that controls and operates a CNC machine. Machine control units offer standard canned cycles as well as special canned cycles.

machining

The process of removing metal to form, shape, or finish a part. Machining processes include turning, drilling, and boring.

MCUs

Machine control unit. A small, powerful computer that controls and operates a CNC machine. MCUs offer standard canned cycles as well as special canned cycles.

minor diameter

The smallest diameter feature of a workpiece. The minor diameter of a thread is indicated by a G76 canned cycle X code.

mode

A programmed function that stays in effect until it is either cancelled or substituted with another function. Most canned cycles function as modes on a CNC machine.

modes

A programmed function that stays in effect until it is either cancelled or substituted with another function. All canned cycles function as modes on a CNC machine.

multiple repetitive cycle

A canned cycle for the lathe that uses a single block of code to automatically execute a series of tool passes. Multiple repetitive cycles include the canned cycles G71, G72, G73, and G76.

overrides

A control that allows a machine operator to adjust a programmed machining variable during execution of the part program. Overrides cannot occur during tapping operations, because they require a synchronized speed and feed rate.

P code

A word in the drilling with dwell G82 canned cycle that indicates how long the tool should dwell inside the hole. P codes are also used in multiple repetitive canned cycles to indicate the starting block number of the final toolpath.

part programs

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.

peck drilling

A drilling operation that periodically retracts the tool to clear chips or flood the hole with coolant. Peck drilling is often used for holes that are three or four times deeper than the drill diameter.

pecks

A single pass of a peck drilling cycle. A complete peck drilling cycle is comprised of a number of pecks.

profile turning

A turning operation that uses a single-point tool to machine the outline of a part feature. Profile turning operations typically require the use of the G73 rough profile turning canned cycle.

Q code

A word in a peck drilling canned cycle that indicates how far to feed the drill into the part for each peck. Q codes are also used to indicate the ending block number of the final toolpath in multiple repetitive canned cycles.

R code

A word in a holemaking canned cycle that describes the location of the R level or clearance plane. An R code also indicates the position from one end of a taper to the other when machining tapers with a G90 turning or G94 facing canned cycle on some CNC lathes.

R level

An imaginary line on the X or Z axis that indicates the top of the cutting tool clearance plane. An R level indicates the safe distance for rapid tool movement from one operation to the next.

R level return

A movement that positions the cutting tool at the R level or clearance plane. R level return occurs when a G99 code is used in a part program.

rapid positions

The quick movement of a machine component to a certain location. Rapid positioning occurs when the cutting tool is not machining into the workpiece.

reaming

The process of enlarging an existing hole with a multipoint tool. Reaming is performed to improve the surface finish and concentricity of a hole.

right-hand tap

A cutting tool that rotates clockwise as it enters a hole to cut a thread. Right-hand taps require the use of the tapping canned cycle G84.

rough boring

A holemaking operation that enlarges an existing hole with a single-point tool that rapidly retracts from the hole after machining. Rough boring often leaves a mark, known as a drag line, along the length of the hole.

roughing

An initial cutting tool pass that emphasizes high material removal rates rather than surface finish and accuracy. Roughing passes are followed by a finishing pass.

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 rotates. On the lathe, the spindle holds the workpiece.

spot drilling

A drilling operation that uses a shorter, sturdier drill to create a small hole that prevents the regular drill from wandering off center. Spot drilling often uses a drill size slightly larger than the hole diameter.

stock

Raw material that is used to make manufactured parts. Stock is available in standard shapes such as long bars, plates, or sheets.

surface finish

The degree of roughness and variation on the surface of a part after it has been manufactured. Surface finish on a part cannot be perfectly smooth, due to irregularities created during machining.

synchronizing

To operate at the same time or rate. Synchronizing feed and speed is required for tapping operations.

tapers

A conical shape with a gradually increasing or decreasing diameter. Tapers can be machined using the G90 turning or G94 facing canned cycle or using a multiple repetitive cycle.

tapping

The process of cutting internal threads in a hole with a rotating multipoint tool. Tapping can be performed on a lathe using the canned cycle G84 or G74 as long as it has the appropriate tapping cutting tool.

threading

A cutting operation that cuts a long, spiraling groove into a cylindrical workpiece with a single-point tool. Threading occurs in fasteners and mating parts so that they fit together.

threads

A long, spiral ridge around the exterior or interior of a cylindrically shaped object. Threads are usually machined to attach a fastener or a part to its mate.

tolerance

An unwanted but acceptable deviation from a given dimension. Both workpieces and gages have specified tolerances.

toolpath

A series of program blocks that describes the movement of a single cutting tool. The toolpath includes multiple tool movements.

turning

A machining operation that rotates a cylindrical workpiece while a single-point tool is guided along the length of the part. Turning can be performed using the G90 canned cycle.

turning centers

A sophisticated CNC lathe that can perform a variety of drilling and milling operations all at the same location. Turning centers usually use live tooling.

turret

A lathe component that holds a number of cutting tools. Turrets rotate or index to place tools in cutting position.

U code

A word in a multiple repetitive cycle that determines the stock remaining along the X axis. A U code, along with a W code, is required to run a G71 rough turning or G72 rough facing cycle.

W code

A word in a multiple repetitive cycle that determines the stock remaining along the Z axis. A W code, along with a U code, is required to run a G71 rough turning or G72 rough facing cycle.

X axis

A linear axis perpendicular to the machine spindle. The X axis usually runs parallel to the workpiece face on a CNC lathe.

X code

A word in a part program that describes a specific position along the X axis. X codes are usually used for both CNC mills and CNC lathes.

Z axis

The linear axis representing coordinate positions along a line parallel to the spindle. The Z axis usually runs parallel to the workpiece centerline on a CNC lathe.

Z code

A word in a part program that describes a specific position along the Z axis. Z codes are usually used for both CNC mills and CNC lathes.

Z depth

The Z axis position that marks the depth of a hole in a holemaking canned cycle. The Z depth is indicated by the Z code.

G73

A code in G code programming that generally activates the rough profile turning canned cycle. The G73 canned cycle is a multiple repetitive cycle.

G73

A code in G code programming that generally activates the rough profile turning canned cycle. The G73 canned cycle is a multiple repetitive cycle.