Chapter Seven, Cutting Tools

Part One of Notes taken while studying Chapter Seven of Machine Shop Basics visit them at www.aubelbooks.com

Chapter Seven

Cutting tools

All machine tool operators need to have a basic knowledge of the cutting action of cutting tools.

Action of Cutting Tools

Cutting tools use a wedging action, the power used in cutting metal is expended in the form heat. When used to make heavy cuts a tool has a small ridge of metal directly over the cutting edge. This metal is much harder then the metal bring cut, coolants help absorb the heat from the cutting edge of the tool, in high-speed production work.

Materials

Here are some materials used for making cutting tools.

Carbon Tool Steel: Less expensive as other cutting tools, and can be used on some types of metal successfully.

High Speed Steel: The most popular cutting tool material, high-speed tools contain tungsten, chromium, vanadium and carbon.

Stellite: These bits can withstand higher cutting speeds then high-speed steel. Stellite is a non-magnetic alloy, harder than common steel (High-Speed) even if heated red hot by fiction, it will not lose its temper. Being harder than high-speed steel, Stellite is more brittle and is used for machining high steel cast iron and bronze.

Carbide: Tips of cutting tools are made of carbide for manufacturing operations where maximum cutting speeds are desired.

Tungsten Carbide: These cutting tools for machining cast iron, alloyed cast iron, bronze, copper, brass, Aluminum, Babbitt, and abrasive nonmetallic materials, hard rubbers and plastics. These tools are so hard they cannot be ground satisfactory on a regular grinding wheel.

Titanium Carbide: a combination of tungsten carbide and titanium carbide are interchangeable with tantalum carbide in its uses.

Shapes and Uses of Cutting Tools

Here are nine popular shapes of lathes cutter bits and their uses.

Left Hand turning tool-opposite of the right hand turning tool for turning in either direction, this tool is used in machine work from left to right.

Round-nose turning tool-used for reducing the diameter of a shaft in the center, this tool is for turning in either direction.

Right-hand turning tool-is the most common type of cutting tool for general lathe work used in machining work; this cutting tool travels from left to right.

Left-hand facing tool-opposite of the right hand tool, and is used for facing the left hand side of the work.

Threading tool- This tool is used to cut threads and the point is ground to a 60-degree angle.

Cutoff tool-is used where a regular turning tool cannot be.

Boring tool-is ground the same as a left hand turning tool; however, the front clearance angle is slightly greater. This is the heel of the tool will rub in the hole of the work.

Inside threading tool-is ground the same way as the screw-threading tool, except that the front clearance angle must be greater.

Terms Related to Cutting Tools

Base- Surface of the shank that bears against the support and takes the tangential pressure of the cut

Chip Breaker- this is to break chips into small pieces, can be an irregularity in the face of the tool or a separate piece attached to the tool or holder.

Cutting Edge- Portion of the face edge along which the chip is separated from the work

Face- Surface on which the chip slides as it is cut from the work

Flank- Surface or surface below and adjacent to the cutting edge

Flat- Straight portion of the cutting edge intended to produce a smooth machine surface.

Heel- Edge between the base and the flank immediately below the face

Neck- An extension of reduced sectional area of the shank.

Nose- A curved face edge

Shank- Portion of the tool back of the face that is supported in the tool post

Chapter Six, Cutting Fluids

Notes taken while studying chap. 6 of Machine Shop Basics visit them at www.audelbooks.com

Chapter 6
Cutting Fluids

In machining operations, cutting fluids reduce temperature and adhesion between the chip and the tool. This avoids thermal expansion and provides easier handling; cutting fluids also keeps away chips from the machining area. Sometimes a lubricant is part of the cutting fluid; this provides a rust proof layer to the finished work piece.

Coolant

A coolant chief purpose is to absorb heat from the work and the cutting tool. Coolant is usually in a liquid form; water has the highest cooling effect of any cutting fluid.

Lubricant

A cooling lubricant is a cutting fluid with the additional property that enables it to act as a lubricant. These materials usually consist of both cooling and lubricating agents, such as soluble oil or glycerin mixed in proper proportions.

Applications of Cutting Fluids

A stream of soluble oil is increases the cutting capacity of an abrasive wheel by preventing it from glazing over, and by carrying off the heat generated by the friction of the wheel on the work. It is important to apply the coolant to the work. A large stream of coolant at slow velocity is preferable to a high stream at high velocity. The cutting fluid should make contact with the work at the exact spot where the cutting is taking place, not above or to one side of the cutting tool.
On machining tools, cutting fluids keep heat from softening the cutting edge of the cutting tool. Cutting fluids cool the cutting tool and make it cut more easily and smoothly. The use of fluids washes away chips, prevents friction and allows higher cutting speeds.

Types of Cutting Fluids
Commonly used cutting fluids

o Lard oil- One of the oldest and best cutting oils, providing excellent lubrication, increased tool life, and provides a smooth finish on the work while preventing rust. Primary used for cutting screw threads, drilling deep holes, and reaming. Its use is somewhat limited because of the expense, the tendency to become rancid, and can cause skin irritation.
o Mineral-lard oil mixtures- Mixtures of various proportions of lard oil and petroleum-base mineral oils use in the place of lard oil alone, they are more fluid, less expensive and almost as effective.
o Mineral oils-Petroleum-based oils- Added with chemicals improving lubrication and anti-welding qualities. They are less expensive than lard oil and mineral oil mixtures.
o Water-soluble oils- Limited to use in rough turning operations, they carry away heat better than lard and minerals oils; however, lubricating qualities are poor. They are mixed with water to form an emulsion and prove to be an excellent low-cost coolant.
o Chemical cutting fluids- These are mixed with water and generally do not contain any petroleum products. The chemicals used provide excellent lubricating and anti-welding properties.
o Low-viscosity oils- Kerosene and other types of oils are used for cutting tough nonferrous metals and alloys such as bronze, aluminum alloys and alloys containing a small percentage of iron such as Monel metal.

Solid Lubricants

Grease-type lubricants are used on band saws to lubricate the sides, back edge and guide bearing especially where high speeds are involved. Graphite is often combined with these lubricants and is supplied in tubes.
Wax and soap lubricants are combined with petroleum substances and are supplied in stick form. A good solid lubricant is recommended for sawing metals, hardwoods ect, where the use of a solid lubricant is preferred to a circulating type.

CHAPTER 5 OF MACHINE SHOP BASICS

CHAPTER 5
GRINDING
NOTES TAKEN WHILE STUDYING CHP5 OF MACHINE SHOP BASICS
VISIT THEM AT www.audelbooks.com
Grinding
By definition, grinding is the process of disintegrating a material and reducing it into small particles of dust by crushing or attrition.
Manufacture of Grinding Wheels
Grinding wheels are made from sandstone, occurs in nature or from man-made abrasives. Natural grindstones are mostly used in glass, cutler, and woodworking edge-tool industries. However, manufactured abrasives wheels have largely replaced natural grindstones in these industries. Because manufactured grinding wheels can be operated at higher speeds, and the grain size, hardness and structure can be controlled.
Manufactured Abrasives Grinding Wheels
Most grinding wheels are made from aluminum oxide and silicon oxide, these are prepared in a similar way. The process starts out with ore from an electric furnace rough crushed into lumps about six inches in diameter. From there the next step is to the abrasive mill, the lumps are further reduced in size to about three fourths in diameter. The final step they are ran through a series steels crushing rolls, the pieces are reduced to grain size for use in grinding wheels and coated abrasive products.
Iron impurities are removed by using magnetic separators, fine abrasive dust and foreign particles are removed by washing with stream and hot water. Washing is important because clean grains mix uniformly with the bond, after washing the abrasive in then dried in continues rotary driers.
The abrasive grains are passed over a series of vibrating screens in the range of 10 to 600 this is the mesh size, which a particle grain will pass though. A screen having 10 mesh openings per linear inch is called a 10-grit size and will have 100 openings per square inch.
Abrasive grains are inspected as they come from the mill for capillary, uniformity of size, strength, and weight per unit volume. The grains are uniformly distributed throughout the bond in the wheel. The structure refers to relative spacing as dense, medium or open, depending on the percentage of abrasive or pores. Wheels of medium structure are best for hard, dense materials open structures are best for heavy cuts and soft, ductile materials that are easily penetrated and require good chip clearance.
Shapes of Grinding Wheels
Grinding wheels are manufactured in nine standard shapes and 12 faces

Straight
Recessed one side
Recessed two sides
Cylinder
Straight cup
Flaring cup
Tapered Two sides
Dish
Saucer

Twelve Standard Grinding wheel faces
Method of Mounting Grinding Wheels
Before mounting grinding wheels should be checked for balance and out of balance wheels cause excessive vibration, causing chatter marks on the ground surface and excessive wear on the bearings and spindle.
Truing and Dressing the Grinding Wheel
To be running true on its own spindle, a wheel should have enough of the cutting face removed in preparation for grinding. With use a wheel will become glazed or loaded then it needs to be dressed, this restores its original shape and clean cutting face. There are three types of wheel dresses used on precision grinding machines. The diamond tool, abrasive wheel and mechanical dresser, the common is the diamond wheel on all types of precision grinders.
Bond types in grinding wheels
The bond in the grinding wheel holds the grains together and supports them while they cut. The greater the amount of bond with respect to the abrasive, the heavier the coating of bond around the grains the harder the wheel. Hard and soft are terms that actually refer to the strength of the bonding wheel. The three types of grinding wheel bond are:

Vitrified
Organic (resinoid, rubber, shellac)
Silicate
Vitrified-Bond Grinding Wheels

Approximately two-thirds of the manufactured grinding wheels are made with a vitrified bond composed of clays and feldspars, and are selected for their fusibility. During the burning process manufacture, a temperature of 1270’f is reached, which is high enough to fuse the clays into molten glass condition. When cooling a span or post of this glass connects each abrasive grain to its neighboring grains to make a strong rigid grinding wheel.
Organic-Bonded Grinding Wheels
Organic-bonded grinding wheels are made from resinoid , rubber of shellac. Resinoid wheels are used in high-speed rough-grinding operations and are the largest percentage of organic-bonding wheels. Straight wheels are used on bench and pedestal grinding, cup wheels and cones are used for cleaning castings and for weld grinding with portable grinders. Reinforced cutoff wheels are used on both cutting-off machines, cutting bar stock and cutting concrete blocks and other masonry materials.
Grinding Wheel Markings
In 1944 a standard system for marking grinding wheels was adopted by grinding wheel manufacturers throughout the country. The markings consists of six parts arranged in this order

o Abrasive type
o Grain size
o Grade
o Structure
o Bond Type
o Bond Modification Symbols

Abrasive types: Abrasive types fall into two groups, letters are used to identify them

o A-Aluminum Oxide
o C-Silicon Carbide

Grain Size: Grain size in wheels range in size from 10 (course) to 600 (fine)
Grade: Grade is indicated by letters of the alphabet ranging from A to Z (soft to Hard)

Grade A to H Soft
I to P Medium
Q to Z Hard

Structure : Structure spacing or grain spacing in grinding wheels is indicated by a number from 1 to 12. The higher numbers indicates more open grain spacing
examples

3 in dense or close grain structure
8 is a wide grain spacing

Bond or Process: the following letters designate the type of bond.

V-Vitrified
B-Retinoid
R-Rubber
E-Shellac
S-Silicate

Bond Modification Symbols: These indicate a particular type of bond that distinguishes it as a variation from a basic bond.

VG (Norton G type of Vitrified bond)
B11 (Norton 11 type of resinoid bond)

Factors Affecting Grinding Wheel Selection
Six items need to be taken into consideration when selecting grinding wheels

1. Abrasive type
2. Grain size
3. Grade
4. Structure
5. Bond type
6. Manufacture’s Record

Hardness of the Metal to be Ground
Abrasive: Aluminum oxide is best suited for grinding steel and steel alloys.
Silicon Carbide grinding wheels are most efficient for grinding cast iron, non-ferrous metals, and non-metallic materials.
Grit Size: Fine grit is best for hard, brittle, and difficult to penetrate materials. Course grit is best for soft ductile, easily penetrated materials.
Grade: For very hard dense materials, use a relatively soft grade-grinding wheel. Hard materials resist the penetration of the abrasive grains and cause them to dull quickly. A soft grade wheel enables worn, dull grains to break away and expose newer, shaper cutting grains. Harder grade grinding wheels should be used for soft, easily cut materials.
Amount of Stock to be removed and Finish Required
Grit size and bond are important in the selection of a wheel depending on the amount of stock to be removed and the finish required.
Grit size: For rough grinding or rapid removal of stock, use a coarse grit. If a high finish and close tolerances are required, use a fine grit size.
Bond: A vitrified bond is best suited for a fast cutting and a commercial finish. Resinoid, rubber of shellac is best for obtaining a high finish.
Operation (Wet or Dry): Generally wet grinding permits the use of grinding wheels at least one grade higher than for dry grinding without danger of burning the work from heat of friction. Water speeds up the work and reduces dust.
Wheel speed: Grinding wheel speed is very important in selecting a wheel and bond as follows.
For speeds, less than 6500 surface feet per minute (sfpm) use vitrified-bonded wheels.
For speeds above 6500, sfpm use an organic-bonded wheel (resinoid, rubber or shellac).
Areas of Grinding Contact
The area of contact between the wheel and the work influences grit size and grade. In general the smaller the area of contact, the harder the grinding wheel should be. For a large area of contact, a coarse grit wheel should be used. If the area of contact is small then a fine-grit wheel should be used.
Severity of the Grinding Operation
Factors that influence the choice of abrasive:
Use a tough abrasive, “regular aluminum oxide for grinding steel and steel alloys under severe conditions.
Use a relatively mild abrasive for light grinding on hard steels.
Use a intermediate abrasive for grinding job of average severity

Abrasives

CHAPTER FOUR
ABRASIVES

Notes made while reading Audel‘s Machine Shop Basics visit them at www.audelbooks.com
Grinding is relativity a new art with most of the development having taken place since the 1890’s. The definition of an abrasive is a substance (i.e. sandpaper, emery) used for grinding polishing etc. Before this, the only abrasives were prepared from sandstone. Because of harder metals and alloys, abrasives that are more efficient were needed.

Natural Abrasives

Emery and corundum are hard natural metals, naturally occurring in aluminum oxide, corundum has larger crystals and contains fewer impurities. These materials were used in grinding wheels until the turn of the century, since then more efficient man-made material started being used.

Manufactured Abrasives

As the need, grinding increases so did producing abrasives whose quality is controlled. Progress has made in the development of bonding materials when ceramic clays and pottery kiln used in grinding wheel manufacture.

Composition of Abrasives

At first emery was used in grinding wheels, it was not until silicon carbide, aluminum oxide, and diamonds were developed to replace emery that true progress was made. Silicon carbide is a mixture of clay and powered coke originally used to polish precious gems. Aluminum oxide or Bauxite was fused electrically into a hard material similar to emery and corundum. Its one advantage is it can be produced in uniform grade and higher purity, 93% to 94% Aluminum oxide. Today Aluminum oxide is used 75% of all grinding wheels of one type or another.

Diamonds

The ability to synthesize diamonds in the laboratory was achieved in 1955, prior to this natural diamonds were used in grinding wheels. The need for diamonds was created by tungsten carbide a material so hard ordinary grinding wheel would not work. Today diamonds wheels are used for grinding carbide, ceramics, glass, stone and some tool steels.
Use of Abrasives in Grinding Wheels

Grinding is the process of disintegrating a material and reducing it into small particles of dust by crushing or attrition. Here are some of the newer abrasives used in grinding wheels.
Silicon Carbide Abrasives

Silicon carbide is made of pure silica and carbon in the form of finely ground coke. When heated in an electric furnace silicon carbide crystals are formed, these are mainly used in a large variety of abrasive and refectory products. Here are some brand names

crystolon
carborundum
carbolon
carbonite
Aluminum Oxide Abrasives

The source of aluminum oxide (Al/2O/3) is Bauxite, which is aluminum, combined with water and varying amounts of impurities. Manufacture of aluminum abrasive is done with Arc-type electric furnaces. The finished product is called a “pig” of crystalline aluminum oxide. Here are some brand names of aluminum oxide abrasives:

Alundum
Aloxite
Lionite
Borolon
Exolon

Diamond Abrasive

Both natural and man-made diamonds have fields of application in which they excel. Diamond grinding wheels are made in the following three different bond types.

Resinoid
Metal
Vitritied

More Notes From Virtual Machine Shop

Notes on Machinery’s Handbook

Source: Virtual Machine Shop

Introduction to the Machinery’s Handbook

The Machinery’s Handbook is necessary in any machinist’s toolbox to be referred to on a regular basis. Here is an example of manufacturing a part and the use of the handbook during the machining process.

The Blueprint

Look at this blueprint

The material on the blueprint to be machined is 4130 steel that has been tempered at 800 degrees. Tensile strength needs to be determined to select the appropriate cutting tool. Find the Hardness of the metal, done by a Rockwell C scale tester, to find this information look in the chapter called Properties, Treatment, and Testing of Materials. Look for 4130 steel tempered at 800 degrees, looking at the table, tensile strength is 186,000 Pounds per square inch. (See table 11b page 469) The next thing to do is find the hardness of 4130 on the Rockwell C scale. Note here that the Brinell hardness is 380, to convert Brinell to Rockwell C scale look at in the Hardness Testing section table 1. A 381 Brinell hardness number equals a hardness of 41 RC on the Rockwell C scale. The chose of a cutting tool a coated carbide cutter would be more suitable.

Cutting Speeds and Feeds

Now the machining can begin, at a point, two questions need asking, they are. What should be the feed rate, and RPM for a 3-inch diameter work piece? Look at table 1 in the chapter on Feeds and Speeds in the Machinery’s handbook. See where 4130 under Material AISI/SAE Designation; remember 4130 has Brinell Hardness of 380 BHN that gives a feed rate of .028 per revolution and a speed of 120 feet per minute. Use this formula to determine the correct RPM to use:

RPM= (CSx4)/Dia. or (125x4)/3

RPM= (500)/3

RPM=166

To find feed rate in inches per minute use this formula

Feed=RPM x IPR (inches per revolution)

Feed= 166 x .028 = 4.65 inches per minute.

Finding Major Diameter

Remember the drawing calls for 1-8 UNC-2A thread on this piece. Here is how to go about finding the major diameter, look on table 3 of Unified Screw Threads on page 1744. The class is 2A, the max diameter is .9980 and the minimum diameter is .9930.

Thread Depth and Compound Angle

The material is going to be machined on a conventional engine lathe, next it has to determined how much to feed the material in for a complete thread. Looking back at table 3 in the Unified screw threads chapter to find the pitch diameter, and the table states for a 1-8UNC-2A thread the pitch diameter has to be between .9168 and .91. Take the average value of these two numbers.

(.9168+.91)/2

(1.8268)/2

=.9134

With a major diameter of .990, a feed in rate of, .990-.9134=, .0766 Note here that four things control thread geometry, pitch, major diameter, pitch diameter and tread angle. The minor diameter is a byproduct of these, so a feed of .0776 will produce some minor diameter not shown in table 3.

We are almost ready to machine the thread; however, the compound slide is set to 29 degrees. The question is how many thousands must the compound be moved to achieve the .0766 depth required? To solve a right angle problem, turn to page 91 in the Machinery Handbook, Solution of Right-angled Triangles. The compound slide is set at 29 degrees use the formula:

Side b; angle A

c=b/coos A

Since the distance to dial in is .0766 and the angle of the compound is 29 degrees, .0766 is side b and 29 angles A, use the above formula and plug in the numbers:

c=.0766/cos29

c=.0875

Measuring Over Wires

To measure the thread pitch diameter use three wires, actually these precisely matched ground steel rods fit on the threads as shown on the stretch below.

M

Then a micrometer is used to measure over the wires, with this reading calculations determine the pitch diameter.

From table 3 in the Unified screw threads chapter it states that the pitch diameter has to be between .9168 and .9100. Look at the table on page 1896, Diameters of Wires for Measuring American Standard Threads, of the Machinery’s Handbook for selecting a working diameter of wires for the 1-8 thread. The table states use a wire set of .0700 diameters to .1125 diameters for this thread. This however would take a great deal of calculating to determine what the measurement over wires should be for a given pitch diameter and wire set. Now look on page 1901 of the Machinery’s Handbook, Dimensions over Wires of Given Diameter for Checking Screw Threads of (U.S. Standard) and the V-Form. The table selects a .090 diameter wire, note that this is within the limits of .0700 and .1125. Using all the noted tables a 1-8 thread with a pitch diameter of .9314 will measure from 1.0535 to 1.0806 over three properly placed .090 diameter wires.

Fits

The other callout on the drawing is for a 2.00 Class RC7 fir. Find table 8a American National Standard Running and Sliding Fits page 659 of the Machinery’s Handbook. For a shaft of 2-inch diameter, the tolerance is from -5.8 to -4 thousands of an inch. Therefore, the diameter must be between

2.-.0058=1.9942 minimum

2-.004=1.9960 maximum

More notes on Planning a CNC program and setup

Planning a CNC Program
When writing a CNC program planning all the steps ahead of time is very important. The machine that is used and the operations done on that machine is the first step in the process.

Consider things like the size of the part to be machined, required horsepower, number of tools needed and the availability of the machine.


The Part and the Tools

The blueprint or drawing of the part is the basis for writing a NC program; dimensions from the drawing are converted directly into a program. A plan has to be developed for each operation on the part that allows for the sequence of tools to be used and the operation each tool will perform.

The use of extra tooling, using the same tool more the once, or having the tools programmed in the wrong order are things to be avoided. Fixtures and holding devices should be planned for early in the process; pay close attention to clamp locations in order to program around them.

Writing the Program
Planning out each operation on the part allow the machinist to prepare the sequence of tools and the operation each tool will perform before actually writing out the program.
In a nutshell a program is simply a series of commands written in the order they are to be executed. The controller interprets, and then acts on these commands one at a time without stopping.
With the operations defined, the tools selected, and the feeds and speeds calculated the last step is to write the program. This can be done on paper or with the aid of a computer; a part set-up sheet is developed with a tool list. Now the machine can be set-up and the parts machined.
Tool Length Offsets on the Mill
What is an Offset?
With a program written for multiple tools it is crucial that there a method accounting for the difference in tool length of each tool used is relayed to the controller. If these differences are not taken into account crashes will happen.
G43
The introduction of the G-code G43 (tool length offset code) is the solution to tool length compensation. G43 “talks “to the CNC controller to look in a special place within its memory for the length of the tools being used. During the setup of the program, the setup person or operator would have “touched off” each tool used in the program, input the value traveled from the tool change position to the Z-zero plane of the part. When M6 tool change is encountered the controller will make all the additions or subtractions necessary that the programmed value of Z0.0 will be adjusted for the tip of each tool to rest perfectly on the Z-zero part plane.

CNC Notes, Introduction to CNC code

Introduction to CNC Code

With Computer Numerical Control (CNC) a machine controller manages the operation of the machine. This includes table motions, spindle speeds, tool changes, and other machining functions. A program written in NC code is how these functions are accomplished. The coded instructions use letters, numbers and symbols (+,-,/…. and so on) to create a program.

A Character

An NC code is the language that is read by the CNC machine’s controller. To insure accuracy there is specific structure to this language, and consists of characters, words, blocks and programs.

Here are the nine character types used in CNC programming

1. letters A thru Z

2. a number or combination of numbers 0 thru 9

3. + plus sign

4. – minus sign

5. . decimal or period

6. : colon

7. ; semi-colon

8. / slash

9. % percent

A Word

Here are some examples of NC words and what they mean, these are used to provide specific commands to a machine.

NC Word Description

F as in F12.0 Feed rate at 12.0 inches per minute

G as in G1 Tool movement in linear interpolation while under feed control

M as in M6 Miscellaneous function in this instant a tool change

N as in N100 Block sequence number

R as in R.25 Arc radius 0.25 radius

S as in S1250 Spindle speed at 1250 RPM

T as in T3 Selection of tool number 3

X as in X2.5 X-axis coordinate, 2.5 inches in the X direction

Y as in Y4.75 Y-axis coordinates 4.75 inches in the Y direction

A Block

A series of words defining a single instruction is called a block, and a block is made up of a word or a combination of words. An end of block character terminates a block, the EOB can be either visible or invisible. Here are some examples of both.

N89 M30 (two word block)

N11 T01 M06 (three word block)

N05 G80 G90 G17 (four word block)

N9 G01 X3.0 Y1.7 F4.0 (Five word block)

With an EOB

N400 G0 X0.2 (three word block with “;” used as an EOB)

N5005 G90 G1 F20 X5 Y2 Z4$ (seven word block with “$” used as an EOB)

A Program

A program is a complete set of coded instructions made up of a series of block needed to completely machine a part.

A program and all of its parts can be equated to the English language as follows:

A character is the same in both CNC Code language and the English language

A word is the combination of characters in both the CNC language and the English language.

A block in CNC Code Language is equivalent to a sentence in the English language, conveying specific thoughts, commands and has punctuation that ends them.

A program in CNC Language is equivalent to complete memo of letter in the English Language. They both are a combination of sentences/blocks that convey complete ideas (English) or completed parts (NC Code).

Address Words

Address codes are a single letter character (A-Z) at the beginning of each word that defines what the computer should do with the numerical data that follows. There are address code for Milling and turning, two address codes are considered major codes they are G-codes and M-codes.

Address codes for Milling and Drilling

A Angular dimension around the X axis

B Angular dimension around the Y axis

C Angular dimension around the Z axis

D Cutter compensation register number

E Angular dimension for special axis

F Feed rate

G Preparatory function (G-codes)

I X axis arc center location

J Y axis arc center location

K Z axis arc center location

L Loop count repeat for canned cycles

N Block number

O Program number or subroutine number

P Dwell time

Q Canned cycle repeat dimension

R Arc radius Or z-axis retract distance

S Spindle speed

T Tool selection number

X primary X motion dimension

Y primary Y motion dimension

Z primary Z motion dimension

Address codes for Turning

A Fourth axis rotary motion

B Linear B axis motion

C Fifth axis rotary motion

D First pass cut depth for threading

E Feed rate

F Feed rate

G Preparatory function (G-codes)

I X axis arc center location

J Canned cycle data

K Z axis arc center location

L Loop count repeat for canned cycles

N Block number

O Program number of subroutine number

P Dwell time

Q Canned cycle repeat dimension

R Arc radius or z-axis retract distance

S Spindle speed

T Tool selection number

U Incremental Z axis motion

V Marco parameter

W Incremental Z axis motion

X primary X motion dimension

Y primary Y motion dimension

Z primary Z motion dimension

G Words

G words or G codes as they are commonly called are the major address codes for preparatory functions involving tool movement and material removal. This includes lineal and circular feed moves, rapid moves, canned cycles and dwell. Here are some of the more commonly used G-codes

G-codes for Milling

Rapid positioning (G00)

Interpolation (G01, G02, G03)

Dwell (G04)

Plane selection (G17, G18, G19)

Automatic Reference Returns (G28, G29)

Cutter compensation (G40, G41, G42)

Tool offset (G43-G49)

Work Coordinate Offset (G52-G59)

Unit Input (G20, G21; or G70, G71)

Fixed canned cycles (G80-G89)

Positioning Input (G90, G91)

Set Work Coordinates (G92)

Return Points (G98, G99)

G-codes for lathes

Rapid positioning (00)

Interpolation (G01, G02, G03)

Dwell (G04)

ZX plane selection (G18)

Unit Input (G20, G21)

Automatic Reference Return (G28, G29)

Tool Nose Radius Compensation (G40, G41, G42)

Work coordinate offset (G52-G59)

Fixed cycles:

Finishing Cycle (G70)

Turning Cycle (G71)

Facing Cycle (G72)

Peck-drilling (G74)

Grooving Cycle (G75)

Threading Cycles (76, G92)

O.D./I.D. turning cycle (G90)

Constant Surface Speed (G96, G97)

Free Rate unit (G98, G99)

M Words

Miscellaneous functions that perform instructions that do not involve tool movement are called M words or more commonly M-codes. Included in this is spindle on and off, tool changes, coolant on and off, along with similar other functions. Here are the more commonly used M-codes

for Milling and Lathes.

M-codes for Milling

Program Stops (M00, M01)

End of Program (M02, M30)

Spindle control (M03, M04, M05, M19)

Tool Change (M06)

Coolant Control (M08, M09)

Clamp Control (M10, M11)

Sub-program Control (M98, M99)

M-codes for Lathes

Program Stops (M00, M01)

End of Program (M02, M03)

Spindle control (M03, M04, M05)

Coolant Control (M08, M09)

Clamp Control (M10, M11)

Turret Rotation (M17, M18)

Tail Stock Control (M21, M22)

Sub-program Control (M98, M99)