Typically, materials are categorized into color-coded groups as shown below. These groups are made up of different types of similar materials. Each of these material types typically consist of numerous subgroups (listed below, under each material type):

Austenitic SS

(200 and 300 series) Nonmagnetic with excellent corrosion resistance and ductility. Hardened by cold-working (not heat-treatable).

Martensitic SS

(400 and 500 series) Magnetic with high strength, hardness, fatigue resistance, and ductility, but only moderate corrosion resistance. Very machinable and hardenable by heat treatment.

Ferritic SS

(400 series) Magnetic with good corrision resistance. Hardened by cold-working (not heat-treatable).

PH SS

(Precipitation-hardening) Has good corrosion resistance and ductility. Can be precipitation hardened to higher strengths than the martensitic grades.

Duplex SS

Has a mixed microstructure of austenite and ferrite. Have higher resistance to corrision and stress-corrosion cracking than austenitic grades.

Wrought Aluminum Alloy

Aluminum alloy “worked” into shape by rolling, extrusion, drawing, forging, etc. High thermal and electrical conductivity, good corrosion resistance. Excellent machinability.

Cast Aluminum Alloy

Directly casted into final form (sand-casting, die or pressure die casting). Contains high levels of silicon to improve cast ability, resulting in abrasiveness.

Magnesium Alloy

Lightest of structural metals. Can be precipitation hardened to improve mechanical properties. Excellent machinability.

Copper Alloy

High thermal and electrical conductivity. Good corrosion and wear resistance. Includes brass (copper-zinc alloy) and bronze (copper-tin alloy).

Low Carbon Steel

(Also called mild steel) Has less than 0. 3% carbon. Used for components that do not require high strength. Improved machinability is found in the 11xx and 12xx series steels.

Medium Carbon Steel

Has 0.3% to o.6% carbon. Used for components requiring higher strength than low-carbon steels. Improved machinability is found in the 11xx and 12xx series steels.

High Carbon Steel

Has more than o.6% carbon. The higher carbon content results in higher strength, hardness, and wear resistance.

Low Alloy Steel

Contain significant amounts of other alloying elements in addition to carbon. Exhibit improved strength, hardness, toughness, wear resistance, corrosion resistance, hardenability, and hot
hardness (compared to carbon steels).

Tool Steel

Specially alloyed steels designed for high strength, impact toughness, and wear resistance. Commonly used for machining and/or forming metals.

Specialty Steel

Generally contain 32% to 67% iron. This group includes low-expansion steel, maraging steel, and some of the iron-based superalloys.

Gray Cast Iron

Contain flake graphite. Moderate strength, but good machinability and damping capacity. Cannot be worked (forged, extruded, rolled, etc.).

Malleable Cast Iron

Good ductility, strength, and shock resistance (better fracture toughness at low temperatures than nodular irons) . Moderate machinability. Can be shaped through cold working.

Nodular Cast Iron

Contain nodular graphite. Good ductility and shock resistance. Moderate machinability.

Nickel Alloy

Commercially pure grades ( or low alloy nickel) such as Nickel 200 and Nickel 201 have excellent corrosion resistance. Nickel alloys generally contain .38% to 76% nickel. Nickel alloys such as Hastelloy, lnconel, and Wacspaloy are classified as superalloys.

Titanium Alloy

Highest strength-to-weight ratio of all metals with good corrosion resistance as well. High thermal resistance that contributes to poor ma.ch inability.

Cobalt Alloy

Generally contains .35% to 65% cobalt. Although not typically as strong as nickel alloys, they retain their strength at higher temperatures.

Tungsten Alloy

Used for high temperature applications due to its very high melting point. High strength at elevated temperatures, but tends to be brittle at low temperatures. Poor oxidation resistance.

The material condition is the form, heat treatment, temper, etc. of the material. Some common forms of heat treatment include:

Aging

Keeping an alloy at an elevated temperature for a long period of time to allow precipitation to take place. See also precipitation hardening.

Annealing

Heating to and holding at a specific temperature and then cooling at a specific rate. Generally used to soften material for cold working. improve machinability, or alter/improve physical and sometimes chemical

Normalizing

Austenitizing a ferrous alloy (heating above the transformation range) and subsequently cooling it in open air to relieve internal stress and provide uniform composition and grain size. Results in a harder, stronger steel than annealing.

Precipitation Hardening

Keeping an alloy at an elevated temperature for a long period of time (see aging) to allow the controlled release of constituents (alloying elements) to form precipitate (fine particles separated from the solid solution) clusters which increase the yield strength of the alloy.

Quenching

Rapidly cooling a metal after heating it above the critical temperature. Usually produces a harder metal in ferrous alloy, while most non-ferrous alloys become softer.

Tempering

Heating to a temperature below the transformation range for a specific time and then allowing it to cool in open air. Usually performed after hardening to reduce excess hardness and increase toughness (ability to absorb energy and plastically deform without breaking).

HBW

Brinell hardness number (BHN) using a 10-mm 3,000 kgf carbide ball (HBW 10/3000)

HBS

Brinell hardness number (BHN) using a 10-mm 500 kgf steel ball (HBS 10/500)

HRC

Rockwell C hardness number (using a 150 kgf load)

HRB

Rockwell B hardness number (using a 100 kgf load)

Equidistant parallel lines that fit with the cut area.*

Equidistant offsets following the shape of the past profile.

* This is the least favorable tool path and it is not recommended. It utilizes both conventional and climb milling. 

Rounded offsets with arcs that pick out slots and corners.

Loops expanding outward to part profile with smaller arcs picking out corners.

The endmill diameter is equivalent to the slot width and the path follows the centerline of the slot.

The endmill diameter is less than the slot width so it can follow a series of arcs. **

** These tool paths utilize a higher ADOC than the others. It is typically safe to use the full endmill LOC.

Follows the part profile after most of the material has been removed during a roughing operation.

Shank (spindle taper)

The upper section of the tool holder t hat fits into the machine tool spindle. This is the “male” interface of the “female” spindle.

Common spindles include:

-CV (also known as Caterpillar ”V-Flange,” or CAT)
-BT (a Japanese standard)
-HSK ( an abbreviation for a German phrase that means “hollow-shank taper”)
-NMTB (National Machine Tool Builders Association)

Flange

The part of the tool holder that the machine tool changer locks onto when moving the tool holder between the tool changer and spindle. It is also referred to as the V-Flange in holders with CV, BT, and HSK.

Holding Section

This is the section of the tool holder that secures the cutting tool inside the tool holder.

Common holders include:

-Weldon (or endmill adapter)
-Shrink-Fit Adaptors
-Hydraulic Chucks
-Milling Chucks
-Press-fit Adaptors
-Collet Chucks

Gauge Length

Distance from the bottom of the machine tool spindle to the bottom of the tool holder (measured when the tool holder is mounted in the machine spindle).

The distance from the end of the holder/collet to the end of the tool. The more the tool sticks out, the less rigid the setup. This results in increased deflection (may require lighter chip loads) and decreased natural

Also known as Step Down or Cut Depth (often expressed as a percentage of ADOC to endmill cutting diameter).

Heavy ADOC

-More tool deflection, requiring lighter chip load
-Difficulty with chip evacuation may require lighter ROOC and/or fewer flutes

Light ADOC

-Less tool deflection, allowing heavier chip load
-Better chip evacuation, allowing increased ROOC and/or more flute

Also known as Step Over or Cut Width (often expressed as a percentage of RDOC to endmill cutting diameter).

The RDOC and TEA have a direct trigonometric relationship to one another.*

Heavy RDOC/TEA

-More cutting work per tool rotation, requiring slower surface speed!
-Difficulty with chip evacuation may require lighter ADOC and/or fewer flutes
-Fewer re-positioning moves, resulting in shorter cycle time

Light RDOC/TEA

-Less cutting work per tool rotation, allowing faster surface speed
-Better chip evacuation, allowing increased ADOC and/or more flutes
-More re-positioning moves, resulting in longer cycle time

*As stated above, there is a direct trigonometric relationship between the radial depth of cut and the tool engagement angle. Also important to understand is how TEA/ROOC affects “chip thinning”.

To learn more about your recommendations, check out our Speeds and Feeds 101 post on our machinist resource blog – In The Loupe.

Before using a cutting tool, it is necessary to understand tool cutting speeds and feed rates, more often referred to as “speeds and feeds.” Speeds and feeds are the cutting variables used in every milling […]